Longitudinal Quantitative Assessment of Retinal Crystalline Deposits in Bietti Crystalline Dystrophy

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Methods We retrospectively reviewed consecutive patients diagnosed with BCD at a single center. Retinal crystalline deposits were quantified from fundus photographs using semi-automated software, which divided the macular area into a central foveal circle, inner ring, and outer ring. We then analyze changes in the amount and intensity of these deposits over a two-year period. Results The study included 30 eyes from 16 patients. Mean crystal intensity was 1.158 ± 1.425% in the central foveal circle, 1.043 ± 1.444% in the inner ring, and 0.990 ± 0.969% in the outer ring, with no significant differences observed between the regions (all P > 0.05). Over the two-year study period, there was a gradual decrease in both the amount and intensity of the crystals in all zones. However, these changes were not statistically significant (all P > 0.05). Conclusions The use of semi-automated software to analyze fundus photographs provided a quantitative method for assessing retinal crystalline deposits in BCD. This longitudinal study enhanced our understanding of the disease’s natural progression. Bietti crystalline dystrophy Inherited retinal disease Longitudinal study Quantification Retinal crystal Figures Figure 1 Figure 2 Figure 3 BACKGROUND Bietti Crystalline Dystrophy (BCD) is a rare, autosomal recessive inherited retinal disease (IRD) characterized by the deposition of numerous yellow-white crystalline materials in the retina, and occasionally in the cornea, associated with atrophy of the retinal pigment epithelium (RPE) and sclerosis of the choroidal vessels [ 1 ]. The disease typically manifests between the second and fourth decades of life and patients experience night blindness, reduced visual acuity, and visual field constriction [ 2 ]. The CYP4V2 gene has been identified as a causative gene for BCD. It encodes a novel 525 amino acid protein, a member of the cytochrome P450 family (family 4, subfamily IV, polypeptide 2), which plays a role in fatty acid metabolism [ 1 ]. This protein is expressed in various tissues, including the human RPE, retina, cornea, and many other tissue and cells, including kidney, liver, lung, and lymphocytes [ 2 , 3 ]. BCD is characterized by a dysregulation of lipid metabolism due to deficiencies of lipid binding or in fatty acid desaturation or elongation, resulting in reduced conversion of fatty acid precursors to n-3 polyunsaturated fatty acids (PUFAs) [ 4 ]. These PUFAs, which are recycled by the RPE cells, are crucial components of the photoreceptor outer segments of the retina [ 3 ]. Although crystalline materials in the posterior pole are a hallmark lesion of BCD, they gradually disappear as chorioretinal atrophy progresses [ 5 ]. The specific pathology of how mutations in CYP4V2 lead to the formation of crystalline materials and subsequent degeneration of the RPE and photoreceptors remains unclear. A recent study highlighted significant intereye symmetry in the area and density of retinal crystalline deposits and areas of absent-autofluorescence in both eyes of patients with BCD [ 6 ]. However, this study by Liu et al. [ 6 ] was cross-sectional and could not determine the temporal sequence of changes in the retinal crystalline deposits. Given the rarity of BCD with a global prevalence of 1 in 67,000 [ 2 , 7 , 8 ] and the scarcity of reports on retinal crystalline deposits and disease mechanisms, more detailed information is necessary to better understand this condition. Moreover, longitudinal studies could provide clinically significant outcome measures for gene and stem cell therapy trials. This study aims to quantitatively evaluate retinal crystalline deposits using semi-automated software on fundus photographs of patients with BCD and to explore the temporal evolution of these deposits in the macular area through a longitudinal analysis. METHODS Participants We retrospectively reviewed the medical records of patients diagnosed with clinically confirmed BCD who visited the Inherited Retinal Disease Clinic at Seoul National University Hospital between January 2005 and December 2021. The study received approval from the Institutional Review Board (IRB) of Seoul National University Hospital (IRB approval number: 2105-086-1219) and adhered to the tenets of the Declaration of Helsinki. Due to the retrospective nature of the study and the use of de-identified patient data, the IRB waived the requirement for written informed consent. The clinical diagnosis of BCD was based on a typical fundus appearance characterized by abundant small, sparkling, yellow-white crystals in the posterior pole accompanied by chorioretinal atrophy, corresponding visual field defects, and full-field electroretinography (ERG) findings. We excluded patients with optical media opacities that could significantly impair fundus image acquisition or those lacking at least two consecutive sets of fundus photographs. Ocular Examination All patients underwent comprehensive ophthalmic examinations, as previously described [ 9 ]. These included the measurement of best-corrected visual acuity (BCVA), slit-lamp biomicroscopy, indirect fundus examination, fundus photography, spectral-domain optical coherence tomography (SD-OCT), visual field testing, and full-field ERG. Fundus photography was performed using a Vx-10 fundus camera (Kowa OptiMed, Tokyo, Japan). SD-OCT images were captured using either a Heidelberg Spectralis (Heidelberg Engineering, Heidelberg, Germany) or a Zeiss Cirrus (Cirrus 4000; Carl Zeiss Meditec, Dublin, California, USA). Full-field ERGs were conducted using gold foil recording electrodes following the International Society for Clinical Electrophysiology of Vision (ISCEV) standard protocols [ 10 ]. BCVA measurements were converted to logarithm of the minimum angle of resolution (logMAR) units for statistical analyses. Molecular Genetic Analysis Molecular genetic tests were conducted using peripheral blood samples from patients with informed consent. Genetic testing included a next-generation sequencing (NGS)-based gene panel and whole exome sequencing (WES). The NGS-based gene panel encompassed 244 genes linked to inherited retinal diseases. WES was carried out by Macrogen in Seoul, Korea. Genomic DNA samples were enriched using the Agilent SureSelect Human All Exon Kit V6 Array (Agilent, Santa Clara, CA, USA) and sequenced using an Illumina NovaSeq 6000 system (Illumina, San Diego, CA, USA). Variant interpretations adhered to the guidelines of the American College of Medical Genetics and Genomics (ACMG) [ 11 ]. If pathogenic mutations in the biallelic CYP4V2 gene were identified, a genetic diagnosis of BCD was confirmed. Image Processing and Analysis Pre-processing of fundus photography was performed to enhance the quantification of retinal crystalline deposits (Fig. 1 a). Contrast Limited Adaptive Histogram Equalization (CLAHE) was utilized to isolate and detect retinal crystalline deposits in fundus images more effectively (Fig. 1 b) [ 12 ]. In CLAHE, after applying a threshold filter, equalization was conducted, resulting in enhanced image contrast. The fovea was defined as a 1-mm-diameter circle, aligned with the Early Treatment of Diabetic Retinopathy Study (ETDRS) grid [ 13 ], and centered using SD-OCT guidance to achieve optimal alignment using retinal vessels as landmarks. The ETDRS grid, which includes three concentric circles with radii of 0.5 mm, 1.5 mm, and 3 mm, was overlaid for regional quantification of retinal crystalline deposits (Fig. 1 c). Following, pre-processing, retinal crystalline deposits were extracted using Medilabel® software (version 1.0; Ingradient Inc., Seoul, Korea). The total area covered by retinal crystalline deposits was determined using an automatic threshold function, displaying retinal crystals as black on a white background (Fig. 1 d). Calibration from pixels to millimeters was performed. Subsequently, the area of retinal crystalline deposits was quantified using the “analyze particle” function in FIJI Image J software (version 1.53; National Institutes of Health, Bethesda, MD, USA) [ 14 ]. Measurements of crystal amount (mm²) were taken in different regions of the ETDRS grid: the central foveal ring (within a 1-mm diameter), the inner ring (between 1 and 3 mm annulus), and the outer ring (between 3 and 6 mm annulus). To evaluate crystal intensity (%), the crystal area was divided by the retinal area of each corresponding region. Furthermore, crystal quantification was undertaken at baseline, 1 year, and 2 years to examine the temporal progression of retinal crystalline deposits. Two blinded graders (S.J.Y. and E.K.L.) independently evaluated all fundus images and quantification of retinal crystalline deposits. Statistical Analysis Statistical analyses were conducted using IBM SPSS version 29.0 (IBM Corp., Armonk, NY, USA). We employed the Kruskal-Wallis and Mann-Whitney U tests with Hochberg correction for pairwise multiple comparisons to analyze the differences in mean crystal amount and intensity between the groups. Continuous variables are presented as mean ± standard deviation. A P -value < 0.05 was considered statistically significant. RESULTS Demographics and Genotype We reviewed the medical records of 21 patients diagnosed with BCD. Of the 42 eyes examined, 12 were excluded from the analysis due to the absence of consecutive fundus photographs, leaving 30 eyes from 16 patients for inclusion. None of the patients in this cohort had a history of taking tamoxifen. The mean age of the participants was 58.31 ± 10.77 years, with the mean age at symptom onset being 46.44 ± 7.86 years. The cohort comprised five males and 11 females. Twelve patients (75.0%) presented with nyctalopia, and six (37.5%) reported a family history of IRDs. The mean initial BCVA was logMAR 1.21 ± 0.88 for the right eye and logMAR 1.28 ± 0.84 for the left eye. The central visual field (CVF) was preserved only in the temporal visual field in 10 eyes (33.3%), 0° < CVF ≤ 5° in 16 eyes (53.3%), and 5° < CVF ≤ 10° in 4 eyes (13.3%). The mean follow-up duration was 6.29 ± 5.40 years. Table 1 displays the demographic and clinical characteristics of the study participants. Table 1 Demographics and baseline ocular characteristics of the study participants. Variable Eyes with BCD Age (years) 58.31 ± 10.77 Age of onset (years) 46.44 ± 7.86 Laterality, RE/LE 15/15 Sex, M/F 5/11 Nyctalopia 12 (75.0%) Familial history 6 (37.5%) BCVA (logMAR) RE 1.21 ± 0.88 LE 1.28 ± 0.84 Central visual field (°) 0° 10 (33.3%) 0° < CVF ≤ 5° 16 (53.3%) 5° < CVF ≤ 10° 4 (13.3%) Follow up duration (years) 6.29 ± 5.40 BCD = Bietti Crystalline Dystrophy; RE = right eye; LE = left eye; M = male; F = female; BCVA = best-corrected visual acuity; logMAR = logarithm of the minimum angle of resolution; CVF = central visual field. Continuous variables are reported as mean ± standard deviation. All other data are numbers (percentages). Genetic analysis was performed on 12 of the 16 participants who provided informed consent (eight using an NGS-based gene panel and four using WES). The most frequent CYP4V2 variant identified was c.802-8_810del17insGC, with an allele frequency of 66.7%. Homozygous c.802-8_810del17insGC (p.Val268Alafs*7) mutations [exon7del] were identified in five patients, and compound heterozygous mutations of c.802-8_810del17insGC with other mutations were detected in six patients. Other pathogenic or likely pathogenic mutations included four known mutations (c.675-1G > A [p.?], c.992A > C [p.H331P], c.810delT [p.A270fs], and c.656delT [p.F189fs]). The variant c.327 + 5G > A (p.?) was identified in two patients and classified as a variant of uncertain significance according to the ACMG guidelines, however, functional impact prediction using in-silico tools showed a higher likelihood of pathogenicity. Table 2 presents the genetic profiles of the 12 patients and the CYP4V2 variants identified. Table 2 Characterization of the disease-causing CYP4V2 variants found. No. Family Allele #1 Allele #2 Zygosity Nucleotide (Protein) ACMG criteria Nucleotide (Protein) ACMG criteria P1 c.802-8_810delinsGC (p.Val268Alafs*7) P c.802-8_810delinsGC (p.Val268Alafs*7) P Homo P3 c.802-8_810delinsGC (p.Val268Alafs*7) P c.675-1G > A (p.?) P Hetero P4 F1 c.802-8_810delinsGC (p.Val268Alafs*7) P c.327 + 5G > A (p.?) VUS Hetero P6 F1 c.802-8_810delinsGC (p.Val268Alafs*7) P c.327 + 5G > A (p.?) VUS Hetero P7 c.802-8_810delinsGC (p.Val268Alafs*7) P c.802-8_810delinsGC (p.Val268Alafs*7) P Homo P9 c.802-8_810delinsGC (p.Val268Alafs*7) P c.992A > C (p.H331P) P Hetero P11 c.802-8_810delinsGC (p.Val268Alafs*7) P c.810delT (p.A270fs) LP Hetero P12 F2 c.802-8_810delinsGC (p.Val268Alafs*7) P c.802-8_810delinsGC (p.Val268Alafs*7) P Homo P13 F2 c.802-8_810delinsGC (p.Val268Alafs*7) P c.802-8_810delinsGC (p.Val268Alafs*7) P Homo P14 c.656delT (p.F189fs) P c.992A > C (p.H331P) P Hetero P15 c.802-8_810delinsGC (p.Val268Alafs*7) P c.992A > C (p.H331P) P Hetero P16 c.802-8_810delinsGC (p.Val268Alafs*7) P c.802-8_810delinsGC (p.Val268Alafs*7) P Homo No. = number; ACMG = American College of Medical Genetics and Genomics; P = pathogenic; LP = likely pathogenic; VUS = variant of uncertain significance; Homo = homozygous; Hetero = heterozygous. Longitudinal Quantitative Analysis of Retinal Crystalline Deposits This section summarizes the serial changes in the average amount of retinal crystals over time and differences in average crystal intensity across various zones of the retina, as illustrated in Table 3 and Fig. 2 . At baseline, the average crystal amount was 0.009 ± 0.011 mm² in the central foveal ring, 0.065 ± 0.091 mm² in the inner ring, and 0.241 ± 0.236 mm² in the outer ring of the ETDRS grid. Over two years, there was a gradual decrease in crystal amount across all zones, with mean values at two years of 0.004 ± 0.005 mm² in the central foveal ring, 0.030 ± 0.052 mm² in the inner ring, and 0.169 ± 0.226 mm² in the outer ring. However, none of these reductions were statistically significant (all P > 0.05). Table 3 Serial changes in average retinal crystal amount over time and differences in average retinal crystal intensity across retinal zones. Crystal amount (mm 2 ) Baseline 1 yr 2 yr P value Baseline vs. 1 yr Baseline vs. 2 yr 1 year vs. 2 yr Central foveal ring 0.009 ± 0.011 0.006 ± 0.011 0.004 ± 0.005 0.645 0.149 0.084 0.779 Inner ring 0.065 ± 0.091 0.040 ± 0.058 0.030 ± 0.052 0.440 0.231 0.101 0.074 Outer ring 0.241 ± 0.236 0.219 ± 0.257 0.169 ± 0.226 0.809 0.420 0.124 0.721 Crystal intensity (%) Central foveal ring Inner ring Outer ring P value Central vs. inner ring Central vs. outer ring Inner vs. outer ring Baseline 1.158 ± 1.425 1.043 ± 1.444 0.990 ± 0.969 0.839 0.851 0.655 0.573 1 yr 0.807 ± 1.385 0.632 ± 0.927 0.898 ± 1.055 0.232 0.401 0.121 0.255 2 yr 0.552 ± 0.653 0.472 ± 0.829 0.694 ± 0.928 0.361 0.475 0.550 0.141 †Analysis of Variance. *Paired t -test. Continuous variables are reported as mean ± standard deviation. Significant values with P < 0.05 are in bold. In terms of mean crystal intensity, which reflects the density of crystals within the retinal area of the ETDRS grid, initial measurements were 1.158 ± 1.425% in the central foveal ring, 1.043 ± 1.444% in the inner ring, and 0.990 ± 0.969% in the outer ring, showing no significant differences between the regions (all P > 0.05). At one and two years, there was a noted decrease in crystal intensity across all zones, although these changes did not reach statistical significance at any time point. Figure 3 depicts a representative case illustrating the serial changes in retinal crystalline deposits alongside the progression of chorioretinal atrophy. The pattern of retinal crystals gradually diminishes over the two-year observation period, concurrent with expanding chorioretinal atrophy. DISCUSSION In this study, we quantitatively analyzed retinal crystalline deposits in a patient cohort with BCD using semi-automated software. Through this longitudinal study, we observed how retinal crystals changed over time. We found that crystal intensity did not significantly differ between sectors of the ETDRS grid at any time point. Additionally, there was a clear trend of decreasing crystal intensity as the disease progressed over the 2-year follow-up period. Despite our understanding of the stages of BCD [ 6 , 8 , 15 , 16 ], knowledge about retinal crystalline deposits remains limited. Previous studies have primarily been qualitative or cross-sectional, with little effort made to quantify crystals or examine their longitudinal changes. The clinical implications of our findings suggest that quantifying retinal crystals could make clinical assessments of BCD patients more practical and provide deeper insight into the pathogenesis and phenotype of the disease. Crystalline retinopathy is not exclusive to BCD and can be associated with various etiological conditions, including genetic, toxic, degenerative, idiopathic, and iatrogenic factors [ 17 ]. Regarding hyperreflective crystalline deposits associated with BCD, Meyer et al. [ 18 ] reported that they appear in the retina and RPE, associated with thickening of the RPE-choriocapillaris complex in OCT images. Similarly, Halford et al. [ 15 ] observed that most crystals are located in the RPE/Bruch membrane complex, with a few crystals found elsewhere in the retina but not in the choroid. Although OCT provides detailed localization of crystals within the retinal layers, changes in the overall appearance of crystalline deposits in patients can be intuitively observed in fundus photographs. The contrast enhancement with CLAHE and the semi-automatic segmentation with Medilabel® software in our study enabled us to capture crystals more effectively than with traditional color fundus photography or retinal examination. Earlier studies on the evolution of crystals indicated that atrophy and thinning of the RPE/Bruch's membrane complex were associated with the disappearance of the crystals. Liu et al. [ 6 ] described manual quantification methods for retinal crystals in patients with BCD and noted a strong degree of intereye symmetry. Despite being a cross-sectional study, they observed a decrease in crystal density in areas of complete RPE atrophy, suggesting a timeline where crystal appearance occurs in the early to mild stages of the disease, with crystal involution corresponding to RPE atrophy in later stages. Halford et al. [ 15 ], through serial SD-OCT imaging, also suggested that the crystals might represent a visible phenotype of metabolic dysfunction in the RPE or photoreceptor cells, with their disappearance possibly linked to cell death. Although we could not perform longitudinal quantification of RPE atrophy in this study and thus directly link it to changes in crystals, this is the first longitudinal quantitative study to show that the intensity of crystals gradually decreased over time across all regions of the posterior pole retina, with crystal disappearance clearly evident in areas of RPE atrophy. It can be speculated that crystals are a phenotypic expression of impaired RPE function, and that regional variations in crystal number and intensity may be useful in predicting areas of impending RPE atrophy and identifying targets for future therapeutic interventions. Several biochemical findings have revealed systemic abnormalities of lipid metabolism in patients with BCD [ 4 , 19 ]. CYP4V2 is a microsomal enzyme with ω-hydroxylase activity on both saturated and PUFAs of medium and long-chains, and this enzyme is expressed in the vast majority of body tissues, especially in the RPE and retina [ 3 , 20 ]. The phenotype of BCD appears to be restricted to the eye and does not affect other organs, suggesting the presence of compensatory enzymes that are absent in the RPE. A disruption in the CYP4V2 gene leads to the accumulation of triglycerides and cholesterol, with a concurrent decrease in the metabolism of n-3 PUFAs, resulting in their accumulation in RPE cells in patients with BCD [ 3 , 20 ]. Alterations in functional CYP4V2 are thought to cause impaired lipid processing in the RPE layer, leading to severe localized dyslipidemia and photoreceptor degeneration. However, the exact pathogenetic mechanisms involved in RPE dysfunction and subsequent damage remain unclear. The precise biochemical composition of crystalline deposits in BCD is still undetermined; however, histopathological studies have reported the presence of crystalline intracellular inclusions in extraretinal lymphocytes and fibroblasts [ 2 , 21 ]. Our study had several limitations. First, the retrospective design could introduce selection bias, potentially accentuating some estimates while masking others. Second, the small sample size limited our ability to detect statistical significance and investigate potential genotype-phenotype correlations. However, given that BCD is a rare IRD and longitudinal studies on this condition are scarce, our efforts to quantify longitudinal changes in retinal crystals in patients with BCD provide a reliable foundation for future studies. Third, although we sought to minimize subjectivity by employing two different blinded graders, manual measurements of crystalline deposits remain limited. Future studies using automated crystal quantification methods are needed to confirm our results. Lastly, we did not include quantitative assessments of RPE atrophy in our analyses due to the retrospective nature of the study. Further research is required to elucidate the correlation between longitudinal changes in RPE atrophy and crystalline deposits in patients with BCD, which will be essential for drawing definitive conclusions about the clinical implications of retinal crystalline deposits. CONCLUSIONS In conclusion, we quantitatively analyzed the longitudinal changes in retinal crystalline deposits in patients with BCD using semi-automated software. We observed that crystal intensity did not significantly differ across different sectors of the posterior pole and that there was a decreasing trend in crystal intensity in all sectors over the 2-year follow-up. However, these changes were not statistically significant. Future studies with larger sample sizes and automated crystal quantification methods are warranted to validate and expand upon our findings. Abbreviations BCD: Bietti crystalline dystrophy; IRD: Inherited retinal disease; RPE: Retinal pigment epithelium; PUFA: Poly-unsaturated fatty acid; IRB: Institutional review board; ERG: Electroretinography; BCVA: Best-corrected visual acuity; SD-OCT: Spectral domain optical coherence tomography; ISCEV: International society for clinical electrophysiology of vision; logMAR: Logarithm of the minimum angle of resolution; NGS: Next generation sequencing; WES: Whole exome sequencing; ACMG: American college of medical genetics and genomics; CLAHE: Contrast limited adaptive histogram equalization; ETDRS: Early treatment of diabetic retinopathy study; CVF: Central visual field Declarations Ethics approval and consent to participate All procedures performed in studies involving human participants were in accordance with the ethical standards of the Seoul National University Hospital (IRB 2105-086-1219) and with the 1964 Helsinki declaration and its later amendments or comparable ethical standards. Informed consent was waived because of the retrospective design of the study and the use of deidentified patient information. Consent for publication Not applicable. Availability of data and materials All data generated or analyzed during this study are included in this published article. Competing interest The authors declare no competing interests. Funding This study was supported by a research grant from the Seoul National University Hospital Research Fund (30-2023-0060), and the Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Science and ICT (Information and Communication Technology, NRF-2021R1F1A1045417). The sponsor or funding organization had no role in the design or conduct of this research. Authors’ contributions All authors have made substantive intellectual contributions to this manuscript. Design and conduct of the study (S.J.Y. and E.K.L.), collection and management of the data (S.J.Y., C.K.Y., U.C.P., K.H.P., and E.K.L.), analysis and interpretation of the data (S.J.Y. and E.K.L.), manuscript preparation (S.J.Y. and E.K.L.), review and approval of the manuscript (C.K.Y., U.C.P., K.H.P., and E.K.L.). All authors read and approved the final manuscript. Acknowledgements Not applicable. References Li A, Jiao X, Munier FL, Schorderet DF, Yao W, Iwata F, et al. Bietti crystalline corneoretinal dystrophy is caused by mutations in the novel gene CYP4V2 . Am J Hum Genet. 2004;74(5):817-26. Kaiser-Kupfer MI, Chan CC, Markello TC, Crawford MA, Caruso RC, Csaky KG, et al. Clinical biochemical and pathologic correlations in Bietti's crystalline dystrophy. Am J Ophthalmol. 1994;118(5):569-82. Nakano M, Kelly EJ, Rettie AE. Expression and characterization of CYP4V2 as a fatty acid omega-hydroxylase. Drug Metab Dispos. 2009;37(11):2119-22. 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Identification, isolation, and characterization of a 32-kDa fatty acid-binding protein missing from lymphocytes in humans with Bietti crystalline dystrophy (BCD). Mol Genet Metab. 1998;65(2):143-54. Nakano M, Kelly EJ, Wiek C, Hanenberg H, Rettie AE. CYP4V2 in Bietti's crystalline dystrophy: ocular localization, metabolism of omega-3-polyunsaturated fatty acids, and functional deficit of the p.H331P variant. Mol Pharmacol. 2012;82(4):679-86. Wilson DJ, Weleber RG, Klein ML, Welch RB, Green WR. Bietti's crystalline dystrophy. A clinicopathologic correlative study. Arch Ophthalmol. 1989;107(2):213-21. Additional Declarations No competing interests reported. Cite Share Download PDF Status: Published Journal Publication published 17 Mar, 2025 Read the published version in BMC Ophthalmology → Version 1 posted Editor invited by journal 10 Jan, 2025 Editor assigned by journal 07 Jan, 2025 Submission checks completed at journal 07 Jan, 2025 First submitted to journal 06 Jan, 2025 You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. We do this by developing innovative software and high quality services for the global research community. Our growing team is made up of researchers and industry professionals working together to solve the most critical problems facing scientific publishing. Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-5777272","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":398850327,"identity":"75626591-c0e3-4ae0-8947-73bdcc3c70d8","order_by":0,"name":"Seung Jun You","email":"","orcid":"","institution":"Seoul National University College of Medicine","correspondingAuthor":false,"prefix":"","firstName":"Seung","middleName":"Jun","lastName":"You","suffix":""},{"id":398850329,"identity":"1bad767f-b2df-4ec8-b08e-f0b3d93ce22a","order_by":1,"name":"Chang Ki Yoon","email":"","orcid":"","institution":"Seoul National University College of Medicine, Seoul National University Hospital","correspondingAuthor":false,"prefix":"","firstName":"Chang","middleName":"Ki","lastName":"Yoon","suffix":""},{"id":398850331,"identity":"c26c4818-2018-486e-8161-56983eba9d81","order_by":2,"name":"Un Chul Park","email":"","orcid":"","institution":"Seoul National University College of Medicine, Seoul National University Hospital","correspondingAuthor":false,"prefix":"","firstName":"Un","middleName":"Chul","lastName":"Park","suffix":""},{"id":398850333,"identity":"f2b8b544-6d91-4e0e-adc5-1bc5e2c72323","order_by":3,"name":"Kyu Hyung Park","email":"","orcid":"","institution":"Seoul National University College of Medicine, Seoul National University Hospital","correspondingAuthor":false,"prefix":"","firstName":"Kyu","middleName":"Hyung","lastName":"Park","suffix":""},{"id":398850335,"identity":"00cc15dc-5d87-4d79-ba13-62347e8247f9","order_by":4,"name":"Eun Kyoung Lee","email":"data:image/png;base64,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","orcid":"","institution":"Seoul National University College of Medicine, Seoul National University Hospital","correspondingAuthor":true,"prefix":"","firstName":"Eun","middleName":"Kyoung","lastName":"Lee","suffix":""}],"badges":[],"createdAt":"2025-01-07 02:53:13","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-5777272/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-5777272/v1","draftVersion":[],"editorialEvents":[{"content":"https://doi.org/10.1186/s12886-025-03962-8","type":"published","date":"2025-03-17T15:57:36+00:00"}],"editorialNote":"","failedWorkflow":false,"files":[{"id":73517764,"identity":"2c2a62b6-cf2b-4784-b804-fb3b6d50629b","added_by":"auto","created_at":"2025-01-10 17:58:55","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":10664308,"visible":true,"origin":"","legend":"\u003cp\u003eQuantitative assessment of retinal crystalline deposits in eyes with Bietti Crystalline Dystrophy. (\u003cstrong\u003ea\u003c/strong\u003e) A color fundus photograph showing greyish chorioretinal atrophy and numerous yellow-white crystalline deposits. (\u003cstrong\u003eb\u003c/strong\u003e) Image contrast enhanced using Contrast Limited Adaptive Histogram Equalization (CLAHE) to better detect retinal crystalline deposits. (\u003cstrong\u003ec\u003c/strong\u003e) An Early Treatment of Diabetic Retinopathy Study (ETDRS) grid overlaid for regional quantification of retinal crystalline deposits. (\u003cstrong\u003ed\u003c/strong\u003e) Retinal crystals extracted as black on a white background using Medilabel® software.\u003c/p\u003e","description":"","filename":"Fig1.png","url":"https://assets-eu.researchsquare.com/files/rs-5777272/v1/4e00152a5c95705a88c05d41.png"},{"id":73519001,"identity":"ab916323-46f6-4da5-b8bf-d7d20153a099","added_by":"auto","created_at":"2025-01-10 18:06:55","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":428342,"visible":true,"origin":"","legend":"\u003cp\u003eSerial changes in the average amount (\u003cstrong\u003ea\u003c/strong\u003e) and intensity (\u003cstrong\u003eb\u003c/strong\u003e) of retinal crystals throughout the follow-up period. Circles, squares, and triangles represent means, while vertical lines denote one standard error of the means.\u003c/p\u003e","description":"","filename":"Fig2.png","url":"https://assets-eu.researchsquare.com/files/rs-5777272/v1/8e928270146e04bb34112947.png"},{"id":73517769,"identity":"17ed6055-41cd-4a03-a681-c00b02e47f14","added_by":"auto","created_at":"2025-01-10 17:58:56","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":11484558,"visible":true,"origin":"","legend":"\u003cp\u003eRepresentative case of a 69-year-old man with Bietti Crystalline Dystrophy. (\u003cstrong\u003ea and d\u003c/strong\u003e) Multiple retinal crystalline deposits observed in the macular area of both eyes at baseline. At 2.5 years (\u003cstrong\u003eb and e\u003c/strong\u003e) and 3.5 years (\u003cstrong\u003ec and f\u003c/strong\u003e), the chorioretinal atrophic region has gradually enlarged (white arrows) compared to the arrangement of retinal vessels (white dotted lines), and retinal crystalline deposits are disappearing.\u003c/p\u003e","description":"","filename":"Fig3.png","url":"https://assets-eu.researchsquare.com/files/rs-5777272/v1/397734296bc0ebf504b70070.png"},{"id":79120660,"identity":"7b8a53b6-b5e8-4e52-be67-72e6acae5af4","added_by":"auto","created_at":"2025-03-24 16:10:40","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":22034989,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-5777272/v1/8ddeed47-22a7-4cf4-bf41-50be69a15318.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"Longitudinal Quantitative Assessment of Retinal Crystalline Deposits in Bietti Crystalline Dystrophy","fulltext":[{"header":"BACKGROUND","content":"\u003cp\u003eBietti Crystalline Dystrophy (BCD) is a rare, autosomal recessive inherited retinal disease (IRD) characterized by the deposition of numerous yellow-white crystalline materials in the retina, and occasionally in the cornea, associated with atrophy of the retinal pigment epithelium (RPE) and sclerosis of the choroidal vessels [\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e]. The disease typically manifests between the second and fourth decades of life and patients experience night blindness, reduced visual acuity, and visual field constriction [\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eThe \u003cem\u003eCYP4V2\u003c/em\u003e gene has been identified as a causative gene for BCD. It encodes a novel 525 amino acid protein, a member of the cytochrome P450 family (family 4, subfamily IV, polypeptide 2), which plays a role in fatty acid metabolism [\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e]. This protein is expressed in various tissues, including the human RPE, retina, cornea, and many other tissue and cells, including kidney, liver, lung, and lymphocytes [\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e, \u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e]. BCD is characterized by a dysregulation of lipid metabolism due to deficiencies of lipid binding or in fatty acid desaturation or elongation, resulting in reduced conversion of fatty acid precursors to n-3 polyunsaturated fatty acids (PUFAs) [\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e]. These PUFAs, which are recycled by the RPE cells, are crucial components of the photoreceptor outer segments of the retina [\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e]. Although crystalline materials in the posterior pole are a hallmark lesion of BCD, they gradually disappear as chorioretinal atrophy progresses [\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e]. The specific pathology of how mutations in \u003cem\u003eCYP4V2\u003c/em\u003e lead to the formation of crystalline materials and subsequent degeneration of the RPE and photoreceptors remains unclear.\u003c/p\u003e \u003cp\u003eA recent study highlighted significant intereye symmetry in the area and density of retinal crystalline deposits and areas of absent-autofluorescence in both eyes of patients with BCD [\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e]. However, this study by Liu et al. [\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e] was cross-sectional and could not determine the temporal sequence of changes in the retinal crystalline deposits. Given the rarity of BCD with a global prevalence of 1 in 67,000 [\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e, \u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e, \u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e] and the scarcity of reports on retinal crystalline deposits and disease mechanisms, more detailed information is necessary to better understand this condition. Moreover, longitudinal studies could provide clinically significant outcome measures for gene and stem cell therapy trials. This study aims to quantitatively evaluate retinal crystalline deposits using semi-automated software on fundus photographs of patients with BCD and to explore the temporal evolution of these deposits in the macular area through a longitudinal analysis.\u003c/p\u003e"},{"header":"METHODS","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e \u003ch2\u003eParticipants\u003c/h2\u003e \u003cp\u003eWe retrospectively reviewed the medical records of patients diagnosed with clinically confirmed BCD who visited the Inherited Retinal Disease Clinic at Seoul National University Hospital between January 2005 and December 2021. The study received approval from the Institutional Review Board (IRB) of Seoul National University Hospital (IRB approval number: 2105-086-1219) and adhered to the tenets of the Declaration of Helsinki. Due to the retrospective nature of the study and the use of de-identified patient data, the IRB waived the requirement for written informed consent. The clinical diagnosis of BCD was based on a typical fundus appearance characterized by abundant small, sparkling, yellow-white crystals in the posterior pole accompanied by chorioretinal atrophy, corresponding visual field defects, and full-field electroretinography (ERG) findings. We excluded patients with optical media opacities that could significantly impair fundus image acquisition or those lacking at least two consecutive sets of fundus photographs.\u003c/p\u003e \u003c/div\u003e\n\u003ch3\u003eOcular Examination\u003c/h3\u003e\n\u003cp\u003eAll patients underwent comprehensive ophthalmic examinations, as previously described [\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e]. These included the measurement of best-corrected visual acuity (BCVA), slit-lamp biomicroscopy, indirect fundus examination, fundus photography, spectral-domain optical coherence tomography (SD-OCT), visual field testing, and full-field ERG. Fundus photography was performed using a Vx-10 fundus camera (Kowa OptiMed, Tokyo, Japan). SD-OCT images were captured using either a Heidelberg Spectralis (Heidelberg Engineering, Heidelberg, Germany) or a Zeiss Cirrus (Cirrus 4000; Carl Zeiss Meditec, Dublin, California, USA). Full-field ERGs were conducted using gold foil recording electrodes following the International Society for Clinical Electrophysiology of Vision (ISCEV) standard protocols [\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e]. BCVA measurements were converted to logarithm of the minimum angle of resolution (logMAR) units for statistical analyses.\u003c/p\u003e\n\u003ch3\u003eMolecular Genetic Analysis\u003c/h3\u003e\n\u003cp\u003e Molecular genetic tests were conducted using peripheral blood samples from patients with informed consent. Genetic testing included a next-generation sequencing (NGS)-based gene panel and whole exome sequencing (WES). The NGS-based gene panel encompassed 244 genes linked to inherited retinal diseases. WES was carried out by Macrogen in Seoul, Korea. Genomic DNA samples were enriched using the Agilent SureSelect Human All Exon Kit V6 Array (Agilent, Santa Clara, CA, USA) and sequenced using an Illumina NovaSeq 6000 system (Illumina, San Diego, CA, USA). Variant interpretations adhered to the guidelines of the American College of Medical Genetics and Genomics (ACMG) [\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e]. If pathogenic mutations in the biallelic \u003cem\u003eCYP4V2\u003c/em\u003e gene were identified, a genetic diagnosis of BCD was confirmed.\u003c/p\u003e\n\u003ch3\u003eImage Processing and Analysis\u003c/h3\u003e\n\u003cp\u003ePre-processing of fundus photography was performed to enhance the quantification of retinal crystalline deposits (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003ea). Contrast Limited Adaptive Histogram Equalization (CLAHE) was utilized to isolate and detect retinal crystalline deposits in fundus images more effectively (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003eb) [\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e]. In CLAHE, after applying a threshold filter, equalization was conducted, resulting in enhanced image contrast. The fovea was defined as a 1-mm-diameter circle, aligned with the Early Treatment of Diabetic Retinopathy Study (ETDRS) grid [\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e], and centered using SD-OCT guidance to achieve optimal alignment using retinal vessels as landmarks. The ETDRS grid, which includes three concentric circles with radii of 0.5 mm, 1.5 mm, and 3 mm, was overlaid for regional quantification of retinal crystalline deposits (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003ec). Following, pre-processing, retinal crystalline deposits were extracted using Medilabel\u0026reg; software (version 1.0; Ingradient Inc., Seoul, Korea). The total area covered by retinal crystalline deposits was determined using an automatic threshold function, displaying retinal crystals as black on a white background (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003ed). Calibration from pixels to millimeters was performed.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eSubsequently, the area of retinal crystalline deposits was quantified using the \u0026ldquo;analyze particle\u0026rdquo; function in FIJI Image J software (version 1.53; National Institutes of Health, Bethesda, MD, USA) [\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e]. Measurements of crystal amount (mm\u0026sup2;) were taken in different regions of the ETDRS grid: the central foveal ring (within a 1-mm diameter), the inner ring (between 1 and 3 mm annulus), and the outer ring (between 3 and 6 mm annulus). To evaluate crystal intensity (%), the crystal area was divided by the retinal area of each corresponding region. Furthermore, crystal quantification was undertaken at baseline, 1 year, and 2 years to examine the temporal progression of retinal crystalline deposits. Two blinded graders (S.J.Y. and E.K.L.) independently evaluated all fundus images and quantification of retinal crystalline deposits.\u003c/p\u003e \u003cdiv id=\"Sec7\" class=\"Section2\"\u003e \u003ch2\u003eStatistical Analysis\u003c/h2\u003e \u003cp\u003eStatistical analyses were conducted using IBM SPSS version 29.0 (IBM Corp., Armonk, NY, USA). We employed the Kruskal-Wallis and Mann-Whitney U tests with Hochberg correction for pairwise multiple comparisons to analyze the differences in mean crystal amount and intensity between the groups. Continuous variables are presented as mean\u0026thinsp;\u0026plusmn;\u0026thinsp;standard deviation. A \u003cem\u003eP\u003c/em\u003e-value\u0026thinsp;\u0026lt;\u0026thinsp;0.05 was considered statistically significant.\u003c/p\u003e \u003c/div\u003e"},{"header":"RESULTS","content":"\u003cdiv id=\"Sec9\" class=\"Section2\"\u003e \u003ch2\u003eDemographics and Genotype\u003c/h2\u003e \u003cp\u003e We reviewed the medical records of 21 patients diagnosed with BCD. Of the 42 eyes examined, 12 were excluded from the analysis due to the absence of consecutive fundus photographs, leaving 30 eyes from 16 patients for inclusion. None of the patients in this cohort had a history of taking tamoxifen. The mean age of the participants was 58.31\u0026thinsp;\u0026plusmn;\u0026thinsp;10.77 years, with the mean age at symptom onset being 46.44\u0026thinsp;\u0026plusmn;\u0026thinsp;7.86 years. The cohort comprised five males and 11 females. Twelve patients (75.0%) presented with nyctalopia, and six (37.5%) reported a family history of IRDs. The mean initial BCVA was logMAR 1.21\u0026thinsp;\u0026plusmn;\u0026thinsp;0.88 for the right eye and logMAR 1.28\u0026thinsp;\u0026plusmn;\u0026thinsp;0.84 for\u003c/p\u003e \u003cp\u003ethe left eye. The central visual field (CVF) was preserved only in the temporal visual field in 10 eyes (33.3%), 0\u0026deg; \u0026lt; CVF\u0026thinsp;\u0026le;\u0026thinsp;5\u0026deg; in 16 eyes (53.3%), and 5\u0026deg; \u0026lt; CVF\u0026thinsp;\u0026le;\u0026thinsp;10\u0026deg; in 4 eyes (13.3%). The mean follow-up duration was 6.29\u0026thinsp;\u0026plusmn;\u0026thinsp;5.40 years. Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e displays the demographic and clinical characteristics of the study participants.\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab1\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 1\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eDemographics and baseline ocular characteristics of the study participants.\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"2\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eVariable\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eEyes with BCD\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eAge (years)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e58.31\u0026thinsp;\u0026plusmn;\u0026thinsp;10.77\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eAge of onset (years)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e46.44\u0026thinsp;\u0026plusmn;\u0026thinsp;7.86\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eLaterality, RE/LE\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e15/15\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eSex, M/F\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e5/11\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eNyctalopia\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e12 (75.0%)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eFamilial history\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e6 (37.5%)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eBCVA (logMAR)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eRE\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e1.21\u0026thinsp;\u0026plusmn;\u0026thinsp;0.88\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eLE\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e1.28\u0026thinsp;\u0026plusmn;\u0026thinsp;0.84\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eCentral visual field (\u0026deg;)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e0\u0026deg;\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e10 (33.3%)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e0\u0026deg; \u0026lt; CVF\u0026thinsp;\u0026le;\u0026thinsp;5\u0026deg;\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e16 (53.3%)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e5\u0026deg; \u0026lt; CVF\u0026thinsp;\u0026le;\u0026thinsp;10\u0026deg;\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e4 (13.3%)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eFollow up duration (years)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e6.29\u0026thinsp;\u0026plusmn;\u0026thinsp;5.40\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003ctfoot\u003e \u003ctr\u003e\u003ctd colspan=\"2\"\u003eBCD\u0026thinsp;=\u0026thinsp;Bietti Crystalline Dystrophy; RE\u0026thinsp;=\u0026thinsp;right eye; LE\u0026thinsp;=\u0026thinsp;left eye; M\u0026thinsp;=\u0026thinsp;male; F\u0026thinsp;=\u0026thinsp;female; BCVA\u0026thinsp;=\u0026thinsp;best-corrected visual acuity; logMAR\u0026thinsp;=\u0026thinsp;logarithm of the minimum angle of resolution; CVF\u0026thinsp;=\u0026thinsp;central visual field.\u003c/td\u003e\u003c/tr\u003e \u003ctr\u003e\u003ctd colspan=\"2\"\u003eContinuous variables are reported as mean\u0026thinsp;\u0026plusmn;\u0026thinsp;standard deviation. All other data are numbers (percentages).\u003c/td\u003e\u003c/tr\u003e \u003c/tfoot\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003eGenetic analysis was performed on 12 of the 16 participants who provided informed consent (eight using an NGS-based gene panel and four using WES). The most frequent \u003cem\u003eCYP4V2\u003c/em\u003e variant identified was c.802-8_810del17insGC, with an allele frequency of 66.7%. Homozygous c.802-8_810del17insGC (p.Val268Alafs*7) mutations [exon7del] were identified in five patients, and compound heterozygous mutations of c.802-8_810del17insGC with other mutations were detected in six patients. Other pathogenic or likely pathogenic mutations included four known mutations (c.675-1G\u0026thinsp;\u0026gt;\u0026thinsp;A [p.?], c.992A\u0026thinsp;\u0026gt;\u0026thinsp;C [p.H331P], c.810delT [p.A270fs], and c.656delT [p.F189fs]). The variant c.327\u0026thinsp;+\u0026thinsp;5G\u0026thinsp;\u0026gt;\u0026thinsp;A (p.?) was identified in two patients and classified as a variant of uncertain significance according to the ACMG guidelines, however, functional impact prediction using in-silico tools showed a higher likelihood of pathogenicity. Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e presents the genetic profiles of the 12 patients and the \u003cem\u003eCYP4V2\u003c/em\u003e variants identified.\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab2\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 2\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eCharacterization of the disease-causing \u003cem\u003eCYP4V2\u003c/em\u003e variants found.\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"7\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c7\" colnum=\"7\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003eNo.\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003eFamily\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colspan=\"2\" nameend=\"c4\" namest=\"c3\"\u003e \u003cp\u003eAllele #1\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colspan=\"2\" nameend=\"c6\" namest=\"c5\"\u003e \u003cp\u003eAllele #2\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c7\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003eZygosity\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eNucleotide (Protein)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eACMG criteria\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003eNucleotide (Protein)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c6\"\u003e \u003cp\u003eACMG criteria\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eP1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003ec.802-8_810delinsGC (p.Val268Alafs*7)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eP\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003ec.802-8_810delinsGC (p.Val268Alafs*7)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003eP\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003eHomo\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eP3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003ec.802-8_810delinsGC (p.Val268Alafs*7)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eP\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003ec.675-1G\u0026thinsp;\u0026gt;\u0026thinsp;A (p.?)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003eP\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003eHetero\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eP4\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eF1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003ec.802-8_810delinsGC (p.Val268Alafs*7)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eP\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003ec.327\u0026thinsp;+\u0026thinsp;5G\u0026thinsp;\u0026gt;\u0026thinsp;A (p.?)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003eVUS\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003eHetero\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eP6\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eF1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003ec.802-8_810delinsGC (p.Val268Alafs*7)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eP\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003ec.327\u0026thinsp;+\u0026thinsp;5G\u0026thinsp;\u0026gt;\u0026thinsp;A (p.?)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003eVUS\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003eHetero\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eP7\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003ec.802-8_810delinsGC (p.Val268Alafs*7)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eP\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003ec.802-8_810delinsGC (p.Val268Alafs*7)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003eP\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003eHomo\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eP9\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003ec.802-8_810delinsGC (p.Val268Alafs*7)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eP\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003ec.992A\u0026thinsp;\u0026gt;\u0026thinsp;C (p.H331P)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003eP\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003eHetero\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eP11\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003ec.802-8_810delinsGC (p.Val268Alafs*7)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eP\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003ec.810delT (p.A270fs)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003eLP\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003eHetero\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eP12\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eF2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003ec.802-8_810delinsGC (p.Val268Alafs*7)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eP\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003ec.802-8_810delinsGC (p.Val268Alafs*7)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003eP\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003eHomo\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eP13\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eF2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003ec.802-8_810delinsGC (p.Val268Alafs*7)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eP\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003ec.802-8_810delinsGC (p.Val268Alafs*7)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003eP\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003eHomo\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eP14\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003ec.656delT (p.F189fs)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eP\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003ec.992A\u0026thinsp;\u0026gt;\u0026thinsp;C (p.H331P)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003eP\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003eHetero\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eP15\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003ec.802-8_810delinsGC (p.Val268Alafs*7)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eP\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003ec.992A\u0026thinsp;\u0026gt;\u0026thinsp;C (p.H331P)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003eP\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003eHetero\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eP16\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003ec.802-8_810delinsGC (p.Val268Alafs*7)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eP\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003ec.802-8_810delinsGC (p.Val268Alafs*7)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003eP\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003eHomo\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003ctfoot\u003e \u003ctr\u003e\u003ctd colspan=\"7\"\u003eNo. = number; ACMG\u0026thinsp;=\u0026thinsp;American College of Medical Genetics and Genomics; P\u0026thinsp;=\u0026thinsp;pathogenic; LP\u0026thinsp;=\u0026thinsp;likely pathogenic; VUS\u0026thinsp;=\u0026thinsp;variant of uncertain significance; Homo\u0026thinsp;=\u0026thinsp;homozygous; Hetero\u0026thinsp;=\u0026thinsp;heterozygous.\u003c/td\u003e\u003c/tr\u003e \u003c/tfoot\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003c/div\u003e\n\u003ch3\u003eLongitudinal Quantitative Analysis of Retinal Crystalline Deposits\u003c/h3\u003e\n\u003cp\u003eThis section summarizes the serial changes in the average amount of retinal crystals over time and differences in average crystal intensity across various zones of the retina, as illustrated in Table\u0026nbsp;\u003cspan refid=\"Tab3\" class=\"InternalRef\"\u003e3\u003c/span\u003e and Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e. At baseline, the average crystal amount was 0.009\u0026thinsp;\u0026plusmn;\u0026thinsp;0.011 mm\u0026sup2; in the central foveal ring, 0.065\u0026thinsp;\u0026plusmn;\u0026thinsp;0.091 mm\u0026sup2; in the inner ring, and 0.241\u0026thinsp;\u0026plusmn;\u0026thinsp;0.236 mm\u0026sup2; in the outer ring of the ETDRS grid. Over two years, there was a gradual decrease in crystal amount across all zones, with mean values at two years of 0.004\u0026thinsp;\u0026plusmn;\u0026thinsp;0.005 mm\u0026sup2; in the central foveal ring, 0.030\u0026thinsp;\u0026plusmn;\u0026thinsp;0.052 mm\u0026sup2; in the inner ring, and 0.169\u0026thinsp;\u0026plusmn;\u0026thinsp;0.226 mm\u0026sup2; in the outer ring. However, none of these reductions were statistically significant (all \u003cem\u003eP\u003c/em\u003e\u0026thinsp;\u0026gt;\u0026thinsp;0.05).\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab3\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 3\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eSerial changes in average retinal crystal amount over time and differences in average retinal crystal intensity across retinal zones.\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"8\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c7\" colnum=\"7\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c8\" colnum=\"8\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eCrystal amount (mm\u003csup\u003e2\u003c/sup\u003e)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eBaseline\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003e1 yr\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003e2 yr\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003e\u003cem\u003eP\u003c/em\u003e value\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c6\"\u003e \u003cp\u003eBaseline vs. \u003c/p\u003e \u003cp\u003e1 yr\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c7\"\u003e \u003cp\u003eBaseline vs. \u003c/p\u003e \u003cp\u003e2 yr\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c8\"\u003e \u003cp\u003e1\u0026nbsp;year vs. \u003c/p\u003e \u003cp\u003e2 yr\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eCentral foveal ring\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e0.009\u0026thinsp;\u0026plusmn;\u0026thinsp;0.011\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0.006\u0026thinsp;\u0026plusmn;\u0026thinsp;0.011\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.004\u0026thinsp;\u0026plusmn;\u0026thinsp;0.005\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e0.645\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e0.149\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e0.084\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e0.779\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eInner ring\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e0.065\u0026thinsp;\u0026plusmn;\u0026thinsp;0.091\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0.040\u0026thinsp;\u0026plusmn;\u0026thinsp;0.058\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.030\u0026thinsp;\u0026plusmn;\u0026thinsp;0.052\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e0.440\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e0.231\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e0.101\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e0.074\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eOuter ring\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e0.241\u0026thinsp;\u0026plusmn;\u0026thinsp;0.236\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0.219\u0026thinsp;\u0026plusmn;\u0026thinsp;0.257\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.169\u0026thinsp;\u0026plusmn;\u0026thinsp;0.226\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e0.809\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e0.420\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e0.124\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e0.721\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eCrystal intensity \u003c/p\u003e \u003cp\u003e(%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eCentral foveal ring\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eInner ring\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eOuter ring\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e\u003cem\u003eP\u003c/em\u003e value\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003eCentral vs. inner ring\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003eCentral vs. outer ring\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003eInner vs. \u003c/p\u003e \u003cp\u003eouter ring\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eBaseline\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e1.158\u0026thinsp;\u0026plusmn;\u0026thinsp;1.425\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e1.043\u0026thinsp;\u0026plusmn;\u0026thinsp;1.444\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.990\u0026thinsp;\u0026plusmn;\u0026thinsp;0.969\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e0.839\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e0.851\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e0.655\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e0.573\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e1 yr\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e0.807\u0026thinsp;\u0026plusmn;\u0026thinsp;1.385\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0.632\u0026thinsp;\u0026plusmn;\u0026thinsp;0.927\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.898\u0026thinsp;\u0026plusmn;\u0026thinsp;1.055\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e0.232\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e0.401\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e0.121\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e0.255\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e2 yr\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e0.552\u0026thinsp;\u0026plusmn;\u0026thinsp;0.653\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0.472\u0026thinsp;\u0026plusmn;\u0026thinsp;0.829\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.694\u0026thinsp;\u0026plusmn;\u0026thinsp;0.928\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e0.361\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e0.475\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e0.550\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e0.141\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003ctfoot\u003e \u003ctr\u003e\u003ctd colspan=\"8\"\u003e\u0026dagger;Analysis of Variance. *Paired \u003cem\u003et\u003c/em\u003e-test.\u003c/td\u003e\u003c/tr\u003e \u003ctr\u003e\u003ctd colspan=\"8\"\u003eContinuous variables are reported as mean\u0026thinsp;\u0026plusmn;\u0026thinsp;standard deviation. Significant values with \u003cem\u003eP\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.05 are in bold.\u003c/td\u003e\u003c/tr\u003e \u003c/tfoot\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eIn terms of mean crystal intensity, which reflects the density of crystals within the retinal area of the ETDRS grid, initial measurements were 1.158\u0026thinsp;\u0026plusmn;\u0026thinsp;1.425% in the central foveal ring, 1.043\u0026thinsp;\u0026plusmn;\u0026thinsp;1.444% in the inner ring, and 0.990\u0026thinsp;\u0026plusmn;\u0026thinsp;0.969% in the outer ring, showing no significant differences between the regions (all \u003cem\u003eP\u003c/em\u003e\u0026thinsp;\u0026gt;\u0026thinsp;0.05). At one and two years, there was a noted decrease in crystal intensity across all zones, although these changes did not reach statistical significance at any time point. Figure\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e depicts a representative case illustrating the serial changes in retinal crystalline deposits alongside the progression of chorioretinal atrophy. The pattern of retinal crystals gradually diminishes over the two-year observation period, concurrent with expanding chorioretinal atrophy.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e"},{"header":"DISCUSSION","content":"\u003cp\u003eIn this study, we quantitatively analyzed retinal crystalline deposits in a patient cohort with BCD using semi-automated software. Through this longitudinal study, we observed how retinal crystals changed over time. We found that crystal intensity did not significantly differ between sectors of the ETDRS grid at any time point. Additionally, there was a clear trend of decreasing crystal intensity as the disease progressed over the 2-year follow-up period. Despite our understanding of the stages of BCD [\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e, \u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e, \u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e, \u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e], knowledge about retinal crystalline deposits remains limited. Previous studies have primarily been qualitative or cross-sectional, with little\u003c/p\u003e \u003cp\u003eeffort made to quantify crystals or examine their longitudinal changes. The clinical implications of our findings suggest that quantifying retinal crystals could make clinical assessments of BCD patients more practical and provide deeper insight into the pathogenesis and phenotype of the disease.\u003c/p\u003e \u003cp\u003eCrystalline retinopathy is not exclusive to BCD and can be associated with various etiological conditions, including genetic, toxic, degenerative, idiopathic, and iatrogenic factors [\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e]. Regarding hyperreflective crystalline deposits associated with BCD, Meyer et al. [\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e] reported that they appear in the retina and RPE, associated with thickening of the RPE-choriocapillaris complex in OCT images. Similarly, Halford et al. [\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e] observed that most crystals are located in the RPE/Bruch membrane complex, with a few crystals found elsewhere in the retina but not in the choroid. Although OCT provides detailed localization of crystals within the retinal layers, changes in the overall appearance of crystalline deposits in patients can be intuitively observed in fundus photographs. The contrast enhancement with CLAHE and the semi-automatic segmentation with Medilabel\u0026reg; software in our study enabled us to capture crystals more effectively than with traditional color fundus photography or retinal examination.\u003c/p\u003e \u003cp\u003eEarlier studies on the evolution of crystals indicated that atrophy and thinning of the RPE/Bruch's membrane complex were associated with the disappearance of the crystals. Liu et al. [\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e] described manual quantification methods for retinal crystals in patients with BCD and noted a strong degree of intereye symmetry. Despite being a cross-sectional study, they observed a decrease in crystal density in areas of complete RPE atrophy, suggesting a timeline where crystal appearance occurs in the early to mild stages of the disease, with crystal involution corresponding to RPE atrophy in later stages. Halford et al. [\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e], through serial SD-OCT imaging, also suggested that the crystals might represent a visible phenotype of metabolic dysfunction in the RPE or photoreceptor cells, with their disappearance possibly linked to cell death. Although we could not perform longitudinal quantification of RPE atrophy in this study and thus directly link it to changes in crystals, this is the first longitudinal quantitative study to show that the intensity of crystals gradually decreased over time across all regions of the posterior pole retina, with crystal disappearance clearly evident in areas of RPE atrophy. It can be speculated that crystals are a phenotypic expression of impaired RPE function, and that regional variations in crystal number and intensity may be useful in predicting areas of impending RPE atrophy and identifying targets for future therapeutic interventions.\u003c/p\u003e \u003cp\u003eSeveral biochemical findings have revealed systemic abnormalities of lipid metabolism in patients with BCD [\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e, \u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e]. \u003cem\u003eCYP4V2\u003c/em\u003e is a microsomal enzyme with ω-hydroxylase activity on both saturated and PUFAs of medium and long-chains, and this enzyme is expressed in the vast majority of body tissues, especially in the RPE and retina [\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e, \u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e]. The phenotype of BCD appears to be restricted to the eye and does not affect other organs, suggesting the presence of compensatory enzymes that are absent in the RPE. A disruption in the \u003cem\u003eCYP4V2\u003c/em\u003e gene leads to the accumulation of triglycerides and cholesterol, with a concurrent decrease in the metabolism of n-3 PUFAs, resulting in their accumulation in RPE cells in patients with BCD [\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e, \u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e]. Alterations in functional CYP4V2 are thought to cause impaired lipid processing in the RPE layer, leading to severe localized dyslipidemia and photoreceptor degeneration. However, the exact pathogenetic mechanisms involved in RPE dysfunction and subsequent damage remain unclear. The precise biochemical composition of crystalline deposits in BCD is still undetermined; however, histopathological studies have reported the presence of crystalline intracellular inclusions in extraretinal lymphocytes and fibroblasts [\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e, \u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eOur study had several limitations. First, the retrospective design could introduce selection bias, potentially accentuating some estimates while masking others. Second, the small sample size limited our ability to detect statistical significance and investigate potential genotype-phenotype correlations. However, given that BCD is a rare IRD and longitudinal studies on this condition are scarce, our efforts to quantify longitudinal changes in retinal crystals in patients with BCD provide a reliable foundation for future studies. Third, although we sought to minimize subjectivity by employing two different blinded graders, manual measurements of crystalline deposits remain limited. Future studies using automated crystal quantification methods are needed to confirm our results. Lastly, we did not include quantitative assessments of RPE atrophy in our analyses due to the retrospective nature of the study. Further research is required to elucidate the correlation between longitudinal changes in RPE atrophy and crystalline deposits in patients with BCD, which will be essential for drawing definitive conclusions about the clinical implications of retinal crystalline deposits.\u003c/p\u003e"},{"header":"CONCLUSIONS","content":"\u003cp\u003eIn conclusion, we quantitatively analyzed the longitudinal changes in retinal crystalline deposits in patients with BCD using semi-automated software. We observed that crystal intensity did not significantly differ across different sectors of the posterior pole and that there was a decreasing trend in crystal intensity in all sectors over the 2-year follow-up. However, these changes were not statistically significant. Future studies with larger sample sizes and automated crystal quantification methods are warranted to validate and expand upon our findings.\u003c/p\u003e"},{"header":"Abbreviations","content":"\u003cp\u003eBCD: Bietti crystalline dystrophy; IRD: Inherited retinal disease; RPE: Retinal pigment epithelium; PUFA: Poly-unsaturated fatty acid; IRB: Institutional review board; ERG: Electroretinography; BCVA: Best-corrected visual acuity; SD-OCT: Spectral domain optical coherence tomography; ISCEV: International society for clinical electrophysiology of vision; logMAR: Logarithm of the minimum angle of resolution; NGS: Next generation sequencing; WES: Whole exome sequencing; ACMG: American college of medical genetics and genomics; CLAHE: Contrast limited adaptive histogram equalization; ETDRS: Early treatment of diabetic retinopathy study; CVF: Central visual field\u003c/p\u003e\n"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eEthics approval and consent to participate\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eAll procedures performed in studies involving human participants were in accordance with the ethical standards of the Seoul National University Hospital (IRB 2105-086-1219) and with the 1964 Helsinki declaration and its later amendments or comparable ethical standards. Informed consent was waived because of the retrospective design of the study and the use of deidentified patient information.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConsent for publication\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eNot applicable.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAvailability of data and materials\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eAll data generated or analyzed during this study are included in this published article.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eCompeting interest\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe authors declare no competing interests.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eFunding\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThis study was supported by a research grant from the Seoul National University Hospital Research Fund (30-2023-0060), and the Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Science and ICT (Information and Communication Technology, NRF-2021R1F1A1045417). The sponsor or funding organization had no role in the design or conduct of this research.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAuthors\u0026rsquo; contributions\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eAll authors have made substantive intellectual contributions to this manuscript. Design and conduct of the study (S.J.Y. and E.K.L.), collection and management of the data (S.J.Y., C.K.Y., U.C.P., K.H.P., and E.K.L.), analysis and interpretation of the data (S.J.Y. and E.K.L.), manuscript preparation (S.J.Y. and E.K.L.), review and approval of the manuscript (C.K.Y., U.C.P., K.H.P., and E.K.L.). All authors read and approved the final manuscript.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAcknowledgements\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eNot applicable.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n\u003cli\u003eLi A, Jiao X, Munier FL, Schorderet DF, Yao W, Iwata F, et al. Bietti crystalline corneoretinal dystrophy is caused by mutations in the novel gene \u003cem\u003eCYP4V2\u003c/em\u003e. Am J Hum Genet. 2004;74(5):817-26.\u003c/li\u003e\n\u003cli\u003eKaiser-Kupfer MI, Chan CC, Markello TC, Crawford MA, Caruso RC, Csaky KG, et al. Clinical biochemical and pathologic correlations in Bietti\u0026apos;s crystalline dystrophy. Am J Ophthalmol. 1994;118(5):569-82.\u003c/li\u003e\n\u003cli\u003eNakano M, Kelly EJ, Rettie AE. Expression and characterization of \u003cem\u003eCYP4V2\u003c/em\u003e as a fatty acid omega-hydroxylase. Drug Metab Dispos. 2009;37(11):2119-22.\u003c/li\u003e\n\u003cli\u003eLee J, Jiao X, Hejtmancik JF, Kaiser-Kupfer M, Gahl WA, Markello TC, et al. The metabolism of fatty acids in human Bietti crystalline dystrophy. Invest Ophthalmol Vis Sci. 2001;42(8):1707-14.\u003c/li\u003e\n\u003cli\u003eOishi A, Oishi M, Miyata M, Hirashima T, Hasegawa T, Numa S, et al. Multimodal Imaging for Differential Diagnosis of Bietti Crystalline Dystrophy. Ophthalmol Retina. 2018;2(10):1071-7.\u003c/li\u003e\n\u003cli\u003eLiu Z, Ayton LN, O\u0026apos;Hare F, Arslan J, Hu ML, Noar AP, et al. Intereye Symmetry in Bietti Crystalline Dystrophy. Am J Ophthalmol. 2022;235:313-25.\u003c/li\u003e\n\u003cli\u003eHu DN. Prevalence and mode of inheritance of major genetic eye diseases in China. J Med Genet. 1987;24(10):584-8.\u003c/li\u003e\n\u003cli\u003eGarcia-Garcia GP, Martinez-Rubio M, Moya-Moya MA, Perez-Santonja JJ, Escribano J. Current perspectives in Bietti crystalline dystrophy. Clin Ophthalmol. 2019;13:1379-99.\u003c/li\u003e\n\u003cli\u003eLee EK, Lee SY, Oh BL, Yoon CK, Park UC, Yu HG. Pigmented Paravenous Chorioretinal Atrophy: Clinical Spectrum and Multimodal Imaging Characteristics. Am J Ophthalmol. 2021;224:120-32.\u003c/li\u003e\n\u003cli\u003eConstable PA, Bach M, Frishman LJ, Jeffrey BG, Robson AG. ISCEV Standard for clinical electro-oculography (2017 update). Doc Ophthalmol. 2017;134(1):1-9.\u003c/li\u003e\n\u003cli\u003eRichards S, Aziz N, Bale S, Bick D, Das S, Gastier-Foster J, et al. Standards and guidelines for the interpretation of sequence variants: a joint consensus recommendation of the American College of Medical Genetics and Genomics and the Association for Molecular Pathology. Genet Med. 2015;17(5):405-24.\u003c/li\u003e\n\u003cli\u003eReza A. Realization of the Contrast Limited Adaptive Histogram Equalization (CLAHE) for Real-Time Image Enhancement. VLSI Signal Processing. 2004;38:35-44.\u003c/li\u003e\n\u003cli\u003eDemirkaya N, van Dijk HW, van Schuppen SM, Abr\u0026agrave;moff MD, Garvin MK, Sonka M, et al. Effect of age on individual retinal layer thickness in normal eyes as measured with spectral-domain optical coherence tomography. Invest Ophthalmol Vis Sci. 2013;54(7):4934-40.\u003c/li\u003e\n\u003cli\u003eSchindelin J, Arganda-Carreras I, Frise E, Kaynig V, Longair M, Pietzsch T, et al. Fiji: an open-source platform for biological-image analysis. Nat Methods. 2012;9(7):676-82.\u003c/li\u003e\n\u003cli\u003eHalford S, Liew G, Mackay DS, Sergouniotis PI, Holt R, Broadgate S, et al. Detailed phenotypic and genotypic characterization of bietti crystalline dystrophy. Ophthalmology. 2014;121(6):1174-84.\u003c/li\u003e\n\u003cli\u003eZhang S, Wang L, Liu Z, Sun H, Li Q, Xing C, et al. Observation of the characteristics of the natural course of Bietti crystalline dystrophy by fundus fluorescein angiography. BMC Ophthalmol. 2021;21(1):239.\u003c/li\u003e\n\u003cli\u003eKovach JL, Isildak H, Sarraf D. Crystalline retinopathy: Unifying pathogenic pathways of disease. Surv Ophthalmol. 2019;64(1):1-29.\u003c/li\u003e\n\u003cli\u003eMeyer CH, Rodrigues EB, Mennel S, Schmidt JC. Optical coherence tomography in a case of Bietti\u0026apos;s crystalline dystrophy. Acta Ophthalmol Scand. 2004;82(5):609-12.\u003c/li\u003e\n\u003cli\u003eLee J, Jiao X, Hejtmancik JF, Kaiser-Kupfer M, Chader GJ. Identification, isolation, and characterization of a 32-kDa fatty acid-binding protein missing from lymphocytes in humans with Bietti crystalline dystrophy (BCD). Mol Genet Metab. 1998;65(2):143-54.\u003c/li\u003e\n\u003cli\u003eNakano M, Kelly EJ, Wiek C, Hanenberg H, Rettie AE. \u003cem\u003eCYP4V2\u003c/em\u003e in Bietti\u0026apos;s crystalline dystrophy: ocular localization, metabolism of omega-3-polyunsaturated fatty acids, and functional deficit of the p.H331P variant. Mol Pharmacol. 2012;82(4):679-86.\u003c/li\u003e\n\u003cli\u003eWilson DJ, Weleber RG, Klein ML, Welch RB, Green WR. Bietti\u0026apos;s crystalline dystrophy. A clinicopathologic correlative study. Arch Ophthalmol. 1989;107(2):213-21.\u003c/li\u003e\n\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":false,"highlight":"","institution":"","isAcceptedByJournal":true,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"bmc-ophthalmology","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"boph","sideBox":"Learn more about [BMC Ophthalmology](http://bmcophthalmol.biomedcentral.com/)","snPcode":"","submissionUrl":"https://www.editorialmanager.com/boph","title":"BMC Ophthalmology","twitterHandle":"BMC_series","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"em","reportingPortfolio":"BMC Series","inReviewEnabled":true,"inReviewRevisionsEnabled":true},"keywords":"Bietti crystalline dystrophy, Inherited retinal disease, Longitudinal study, Quantification, Retinal crystal","lastPublishedDoi":"10.21203/rs.3.rs-5777272/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-5777272/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003ch2\u003eBackground\u003c/h2\u003e \u003cp\u003eThis study aims to quantitatively analyze retinal crystalline deposits in patients with Bietti Crystalline Dystrophy (BCD) and examine their progression over time in a longitudinal study.\u003c/p\u003e\u003ch2\u003eMethods\u003c/h2\u003e \u003cp\u003eWe retrospectively reviewed consecutive patients diagnosed with BCD at a single center. Retinal crystalline deposits were quantified from fundus photographs using semi-automated software, which divided the macular area into a central foveal circle, inner ring, and outer ring. We then analyze changes in the amount and intensity of these deposits over a two-year period.\u003c/p\u003e\u003ch2\u003eResults\u003c/h2\u003e \u003cp\u003eThe study included 30 eyes from 16 patients. Mean crystal intensity was 1.158\u0026thinsp;\u0026plusmn;\u0026thinsp;1.425% in the central foveal circle, 1.043\u0026thinsp;\u0026plusmn;\u0026thinsp;1.444% in the inner ring, and 0.990\u0026thinsp;\u0026plusmn;\u0026thinsp;0.969% in the outer ring, with no significant differences observed between the regions (all \u003cem\u003eP\u003c/em\u003e\u0026thinsp;\u0026gt;\u0026thinsp;0.05). Over the two-year study period, there was a gradual decrease in both the amount and intensity of the crystals in all zones. However, these changes were not statistically significant (all \u003cem\u003eP\u003c/em\u003e\u0026thinsp;\u0026gt;\u0026thinsp;0.05).\u003c/p\u003e\u003ch2\u003eConclusions\u003c/h2\u003e \u003cp\u003eThe use of semi-automated software to analyze fundus photographs provided a quantitative method for assessing retinal crystalline deposits in BCD. This longitudinal study enhanced our understanding of the disease\u0026rsquo;s natural progression.\u003c/p\u003e","manuscriptTitle":"Longitudinal Quantitative Assessment of Retinal Crystalline Deposits in Bietti Crystalline Dystrophy","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-01-10 17:58:51","doi":"10.21203/rs.3.rs-5777272/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"editorInvited","content":"","date":"2025-01-10T09:48:39+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2025-01-07T11:42:54+00:00","index":"","fulltext":""},{"type":"checksComplete","content":"","date":"2025-01-07T11:40:12+00:00","index":"","fulltext":""},{"type":"submitted","content":"BMC Ophthalmology","date":"2025-01-07T02:46:08+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"bmc-ophthalmology","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"boph","sideBox":"Learn more about [BMC Ophthalmology](http://bmcophthalmol.biomedcentral.com/)","snPcode":"","submissionUrl":"https://www.editorialmanager.com/boph","title":"BMC Ophthalmology","twitterHandle":"BMC_series","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"em","reportingPortfolio":"BMC Series","inReviewEnabled":true,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"d737a787-e4fc-44ca-8957-e7c51b785fef","owner":[],"postedDate":"January 10th, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"published-in-journal","subjectAreas":[],"tags":[],"updatedAt":"2025-03-24T16:05:59+00:00","versionOfRecord":{"articleIdentity":"rs-5777272","link":"https://doi.org/10.1186/s12886-025-03962-8","journal":{"identity":"bmc-ophthalmology","isVorOnly":false,"title":"BMC Ophthalmology"},"publishedOn":"2025-03-17 15:57:36","publishedOnDateReadable":"March 17th, 2025"},"versionCreatedAt":"2025-01-10 17:58:51","video":"","vorDoi":"10.1186/s12886-025-03962-8","vorDoiUrl":"https://doi.org/10.1186/s12886-025-03962-8","workflowStages":[]},"version":"v1","identity":"rs-5777272","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-5777272","identity":"rs-5777272","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}