Parapapillary choroidal dense pigmentation in young healthy eyes: a cross-sectional study

Parapapillary choroidal dense pigmentation in young healthy eyes: a cross-sectional study | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Research Article Parapapillary choroidal dense pigmentation in young healthy eyes: a cross-sectional study Yuki Uto, Takehiro Yamashita, Kazuki Fujiwara, Aiko Iwase, Hiroto Terasaki, and 2 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-8487176/v1 This work is licensed under a CC BY 4.0 License Status: Under Review Version 1 posted 11 You are reading this latest preprint version Abstract Background Some eyes with parapapillary choroidal dense pigmentation (PCP) have a pigmented conus visible on color fundus photography. This study aimed to determine the prevalence of PCP in young healthy eyes and examine its relationships with axial length, optic disc tilt, and conus area. Methods This prospective, observational, cross-sectional study included the right eyes of 133 participants, who were examined between November 1, 2010 and February 20, 2012. Among them, 117 right eyes of 117 patients were finally analyzed. Participants underwent comprehensive ophthalmologic examinations, including axial length measurement, fundus photography, and optic disc optical coherence tomography (OCT). Based on their color fundus photographs and optic disc cross-sectional OCT images, eyes were categorized into the non-PCP, temporal-PCP, and circum-PCP groups. Optic disc tilt was evaluated using a sine curve based on the retinal nerve fiber layer B-scan images. The conus area in the color fundus images was calculated using ImageJ and corrected using Bennett's formula. The Steel–Dwass test was used to perform multiple comparisons of the axial length, optic disc tilt, and conus area among the three groups. Results The mean age and axial length of the participants were 25.8 years and 25.5 mm, respectively. Of the 117 eyes, 49, 17, and 51 had non-PCP, temporal-PCP, and circum-PCP, respectively. The axial length (p = 0.011) and conus area (p = 0.047) were shorter and smaller, respectively, for the circum-PCP group than for the non-PCP group. No significant differences were observed in the other intergroup comparisons. Conclusions The eyes with circumferential PCP had shorter axial lengths and smaller conus areas than those without. parapapillary choroidal dense pigmentation pigmented conus axial length Figures Figure 1 Figure 2 Background Hyper- and hypopigmentation around the optic nerve head was reported by Jonas et al. in 1988, and these were named parapapillary atrophy alpha (PPA alpha) [ 1 , 2 ]. Irregular pigmentation, PPA alpha, was subsequently reported to be associated with relative scotoma [ 3 ] and more extensive in eyes with early glaucoma and ocular hypertension than in normal eyes [ 4 , 5 ]. However, its frequency and size did not differ between the eyes with normal tension glaucoma and normal eyes [ 6 ]. A study reported that PPA alpha was detected in all 47 eyes with open-angle glaucoma, and its area was significantly correlated with the mean deviation of standard automated perimetry [ 7 ]. Histological examination of human eyes has revealed that PPA alpha is associated with thickening and thinning of the retinal pigment epithelium (RPE) [ 8 ]. Dichtl et al. reported that PPA alpha is located outside PPA beta and in a specific part of the RPE layer [ 9 ]. Furthermore, a long-term observational study in rhesus monkeys showed that the PPA beta increased in size, but the PPA alpha remained unchanged in size and frequency in a long-term observational study of rhesus monkeys [ 10 ]. A cross-sectional population study reported that the prevalence of zone alpha decreased by 0.4% per 10 years of age [ 11 ]. Jonas et al. reported an increase of approximately 0.6% in the PPA alpha area based on the findings of the Beijing study, which involved a 5-year follow-up. This increase was associated with older age and the coexistence of zone beta [ 12 ]. We have been studying individual differences in the fundus of healthy young adults [ 13 – 15 ]. We observed a ring-shaped pigmented band around the optic disc (Fig. 1 b) that was distinct from PPA alpha. This ring-shaped pigmented band is continuous with PPA alpha, as shown in Fig. 1 b. It appears black myopic conus in some eyes. Some eyes had a pigmented band around the entire optic disc, whereas others had it only on the temporal side (Fig. 1 c). On horizontal cross-sectional OCT image, there are no IS/OS line and thin RPE layer in the black myopic conus on the temporal side. And the IS/OS line is thin and RPE layer isn’t thick in the black area on the nasal side (Fig. 1 d). This suggests that the black area observed on the fundus photograph is attributable to a cause other than PPA alpha, which involves thickening of the RPE. The choroidal pigments are the only parts of the fundus structure that appear black, other than the RPE. Therefore, we named this pigment band observed in the fundus as the parapapillary choroidal dense pigmentation (PCP). This study investigated the relationships between the axial lengths, optic disc tilts, and conus areas of eyes with non-PCP, temporal-PCP, and circumferential-PCP. Materials and methods Study design and study population This prospective, cross-sectional observational study enrolled 133 participants. Only right eyes were included. Examinations were performed from November 2010 through February 2012. Individuals with no history of ocular disease were enrolled, based on a review of medical records and comprehensive ophthalmic examinations. The eligibility criteria were: ages of 20–40 years; healthy eyes as determined by slit-lamp biomicroscopy, ophthalmoscopy, and optical coherence tomography (OCT); best-corrected visual acuity of ≥ 0.1 logarithm of the minimum angle of resolution units; and intraocular pressure of ≤ 21 mmHg. The exclusion criteria were: eyes with ocular diseases such as glaucoma, pathologic myopia, and optic disc anomaly; known systemic diseases such as hypertension and diabetes; visual field defects; prior refractive or intraocular surgery; and poor OCT or fundus image quality. Eyes were excluded for the following reasons: glaucoma (n = 1), superior segmental optic disc hypoplasia (n = 3), and a history of refractive surgery (n = 3). An additional nine eyes were omitted because fundus parameters could not be reliably evaluated. The data of 117 eyes (80 male and 37 female) were used for the analyses. Measurements Each subject underwent a standardized set of ophthalmic examinations. These comprised slit-lamp biomicroscopy, fundus evaluation, intraocular pressure assessment with a pneumotonometer (CT-80; Topcon, Tokyo, Japan), and ultrasonic measurement of axial length (AL-2000; TOMEY, Nagoya, Japan). Objective refraction was obtained using an autorefractometer/keratometer (KR-8800; Topcon), and spherical equivalent values were used for analysis. Color fundus photographs were obtained using the TRC-50LX (TOPCON, Tokyo, Japan). Color fundus photographs and the RNFL 3.4 mm circle scans were obtained using the Topcon 3D OCT-1000 Mark II (TOPCON, Tokyo, Japan). A Spectralis OCT device (Heidelberg Engineering, Germany) was used to obtain scanning laser ophthalmoscopy (SLO) images and cross-sectional views of the optic disc. The scan pattern was centered on the optic nerve head and comprised 73 horizontal B-scans spanning 15 degrees. The averages of the data of seven B-scans were obtained and used. Built-in image registration and eye-tracking functions were applied to minimize motion artifacts during image acquisition. Image quality was assessed by the operator, with confirmation of appropriate SD-OCT B-scan positioning within the image frame, proper centering on the optic nerve head, and an adequate quality score (> 20). The images were reacquired when necessary. The color fundus ophthalmoscopic and SLO fundus images were aligned using PowerPoint software based on the vascular pattern. The Spectralis OCT software was used to process and optimize SLO images, color fundus photographs, and cross-sectional OCT scans. Assessment of the PCP, conus area, and optic disc tilt PCP was assessed based on evaluation of color fundus photographs and cross-sectional images of the optic disc. The PCP was defined based on the presence of a dark black parapapillary circular pigment band on ophthalmoscopy and dense choroidal stroma with low choroidal vessel density on OCT. Eyes without these features were allocated to the non-PCP group (Fig. 1 a). Those with these features on the temporal side of the optic disc were allocated to the temporal-PCP group (Fig. 1 c), and those with these features on the circumference of the optic disc were allocated to the circum-PCP group (Fig. 1 b, d). The PCP and conus were independently assessed by two raters (KF and TY). The third rater (HT) determined the type of PCP in cases of disagreement. Optic disc tilt was quantified according to a method previously reported by our group [ 14 ]. The optic disc tilt was quantified using the sine curve method based on the RNFL 3.4-mm circle scan, B-scan images obtained using the Topcon 3D OCT-1000 Mark II (TOPCON, Tokyo, Japan). The RPE course was plotted manually on the B-scan images. The coordinates of each pixel were determined automatically using ImageJ software. The coordinate system of the B-scan images was transformed such that the wave center served as the new origin. The converted data were fitted to the following sine wave equation using the curve fitting program of ImageJ: $$\:y=a\times\:\text{sin}\:(b\times\:x-c)$$ The amplitude (a) of the sine curve was defined as the degree of optic disc tilt. The conus area was measured from the fundus photographs using ImageJ. The image size decreases with increasing axial length because the fundus is farther from the camera. The magnification effect of the axial length was adjusted using Bennett’s formula (3.12 × 0.01306 × 100%/mm) [ 15 , 16 ]. Statistical analyses The intra-rater agreement for the PCP was determined using the weighted Cohen’s kappa coefficient. The Kruskal–Wallis one-way analysis of variance and Steel–Dwass multiple comparison tests were used to determine the significance of the differences in the axial length, conus area, and optic disc tilt among the groups. Statistical analyses were performed using R (version 3.0.2; The R Foundation for Statistical Computing, Vienna, Austria). Statistical significance was set at p < 0.05. Ethics This study was approved by the Ethics Committee of Kagoshima University Hospital (registration number:22–72) on September 30, 2010. All the procedures conformed to the tenets of the Declaration of Helsinki. We obtained written informed consent from all participants after explaining the procedures. Results The demographic information of the patients is provided in Table 1 . The mean age and axial length of the patients were 25.8 years and 25.5 mm, respectively. The number of eyes without PCP, with temporal-PCP, and with circum-PCP were 49, 17, and 51, respectively. The inter-rater agreement for PCP was high (kappa = 0.81). The axial length of the circum-PCP group was significantly shorter than that of the non-PCP group (p = 0.011). However, the differences between the non-PCP and temporal-PCP groups (p = 0.914) and between the temporal-PCP and circum-PCP groups (p = 0.195) were not significant (Fig. 2 a). The optic disc tilt did not significantly differ among the three groups (non vs. temporal, p = 0.061; temporal vs. circum, p = 0.729; non vs. circum, p = 0.108) (Fig. 2 b). The conus area was significantly smaller for the circum-PCP group than for the non-PCP group (p = 0.047). However, the differences between the non-PCP and temporal-PCP groups (p = 0.908) and between the temporal-PCP and circum-PCP groups (p = 0.351) were not significant (Fig. 2 c). Table 1 Participant characteristics Mean ± standard deviation or Median (interquartile range) Range Age (years) 25.8 ± 4.0 22–40 Sex (male/female) 80 / 37 Spherical equivalent (diopters) -4.72 ± 3.33 -14.25-0.50 Axial length (mm) 25.45 ± 1.42 22.43–30.42 PCP (non/temporal/circum) 49 / 17 / 51 Optic disc tilt (pixels) 37.69 ± 17.19 8.80–80.77 Conus area (pixels) 377.79 (0.00, 794.06) 0.00–4194.98 PCP: parapapillary choroidal dense pigmentation Discussion This study presents the first characterization of PCP, a new morphological feature in young healthy eyes. We found a significant association between the circumferential PCP pattern and shorter axial length and smaller conus area. These results suggest that PCP may be a feature of less ocular elongation, distinguishing it from established myopic changes, and requires further investigation into its choroidal origin. The axial length and conus area were shorter and smaller, respectively, for the circum-PCP group than in the non-PCP group. These results suggest that circum-PCP may be one of the hyperopic features. Myopic features [ 17 ] include myopic conus (PPA beta, gamma, and delta zones) [ 18 ], optic disc tilt [ 14 ], tessellation [ 19 ], vessel shift toward the fovea [ 13 ], and peripapillary nerve fiber elevation [ 15 ]. However, a few special hyperopic features have been reported in the fundus. Hyperopia is a refractive state of an eye with less eyeball elongation during growth [ 20 , 21 ]. The choroid is very thick during infancy, but it gradually thins as the eyeball expands during growth [ 22 ]. This is easy to understand if you imagine a balloon inflating. For example, the area around the inlet of the green balloon is darker than the rest of the balloon. The morphology is similar when the optic disc is considered the inlet of the eyeball, with a ring-shaped area of concentrated choroidal pigment around the optic disc. A short axis and small conus suggest less bulging of the eyeball. The choroidal pigment remains dark around the disc in such eyes, creating a ring-shaped black area that may result in PCP. The inlet of the balloon appears darker due to its weak inflation and thick wall. Which is the greater factor in PCP? The choroid in the PCP area appears to be rich in stromal components rather than thick, as observed in the OCT images (Figs. 1 b–d). The choroidal vascular component is abundant up to the optic disc in eyes without PCP (such as those in Fig. 1 a), but the stromal component is scant. The proportions of the stromal components in the choroid vary greatly among individuals [ 22 , 23 ]. The stromal and vascular components become thinner as axial length increases [ 23 , 24 ]. This results in the visibility of the large choroidal vessels, which causes stronger tessellation and a redder fundus [ 25 ]. PPA alpha was present in 98.6% of the cases in an epidemiological study involving Indians [ 26 ]. This study focused on Japanese participants, whose fundus pigmentation is darker than that of Westerners. PCP may be present in eyes with dark fundus pigmentation and weak ocular dilation due to individual and racial differences. Further research is needed to investigate the relationship between the ratio of choroidal stromal and vascular components [ 23 ] and PCP in various ethnic groups. The axial length of the non-PCP group was longer than that of the circum-PCP group. This suggests that myopic fundus changes attenuate PCP. The conus area was larger for the group without PCP than for the group with PCP. Axial elongation causes the choroid to become paper-thin on the temporal side of the optic disc, the sclera becomes visible, resulting in a whitish myopic conus [ 18 ]. The nerve fibers on the nasal side of the optic disc are elevated and appear whitish in eyes with peripapillary nerve fiber elevation [ 15 ]. This may reduce the visibility of the choroid and the apparent blackness of the fundus. Optic disc tilt is also a myopic change, and we expected the circum-PCP group to have greater optic disc tilt than the non-PCP group. However, the difference was not significant. This suggests that optic disc tilt has less effect on PCP than axial length and conus area. Further research is needed to investigate the relationship between myopic changes associated with axial elongation during growth and changes in PCP. The PPA alpha reported by Jonas et al. [ 1 , 2 ] may be influenced by RPE irregularity on the temporal side of the optic disc. However, the fundus findings in Fig. 1 show a black ring around the optic disc that is connected to PPA alpha. Therefore, RPE irregularity around the optic disc is unlikely. Moreover, the term PPA is inappropriate because PCP is not an atrophic change. PCP is a fundus finding derived from choroidal pigment and must be distinguished from the RPE irregularity. This study has some limitations. First, it was a cross-sectional correlation study, and the chronological changes in PCP could not be observed. Second, it involved a young Japanese population. An epidemiological study showed that the Japanese population was the most myopic [ 27 ]. PCP may be common in young healthy eyes, but the findings of this study may not be generalizable to other ethnic groups. Conclusions This study reports PCP, a fundus finding related to choroidal pigment around the optic disc. PCP may be observed in hyperopic eyes and may serve as an indicator of individual differences in fundus pigment. However, many aspects of PCP remain unclear, and further research is needed to explore ethnic differences, its relationship with quantified choroidal structure, and its association with ocular diseases. Abbreviations OCT, ocular coherence tomography PCP, parapapillary choroidal dense pigmentation PPA alpha, parapapillary atrophy alpha RPE, retinal pigment epithelium Declarations Ethics approval and consent to participate This study was approved by the Ethics Committee of Kagoshima University Hospital and registered with the University Hospital Medical Network Clinical Trials Registry (registration number: UMIN000007154). All the procedures conformed to the tenets of the Declaration of Helsinki. We obtained written informed consent from all participants after explaining the procedures. Consent for publication Not applicable. Availability of data and materials The datasets used and/or analyzed during the current study are available from the corresponding author on reasonable request. Competing interests The authors have no conflicts of interest. The authors have no financial disclosures. Funding This work was supported in part by JSPS KAKENHI grant 15H04996 and 25K12838. The funders had no role in the study design, data collection and analysis, decision to publish, or manuscript preparation. Authors' contributions Conceptualization and Methodology, T.Y. and A.I.; Data Curation, T.Y. and K.N.; Formal Analysis, T.Y. and Y.U.; Writing – Original Draft Preparation, T.Y. and Y.U.; Writing – Review & Editing, H.T., A.I. and T.S. Acknowledgements We want to thank Editage (www.editage.jp) for English language editing. Authors' information (optional) References Jonas JB, Gusek GC, Naumann GO. Die parapapilläre Region in Normal- und Glaukomaugen. I. Planimetrische Werte von 312 Glaukom- und 125 Normalaugen [The parapapillary region of normal and glaucoma eyes. I. Planimetric values of 312 glaucoma and 125 normal eyes]. Klin Monbl Augenheilkd German. 1988;193:52–61. Jonas JB, Naumann GO. Die parapapilläre Region in Normal- und Glaukomaugen. II. 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Additional Declarations No competing interests reported. Cite Share Download PDF Status: Under Review Version 1 posted Editorial decision: Revision requested 30 Mar, 2026 Reviews received at journal 28 Mar, 2026 Reviewers agreed at journal 19 Mar, 2026 Reviewers agreed at journal 18 Mar, 2026 Reviewers agreed at journal 01 Mar, 2026 Reviews received at journal 07 Feb, 2026 Reviewers agreed at journal 01 Feb, 2026 Reviewers agreed at journal 26 Jan, 2026 Reviewers invited by journal 21 Jan, 2026 Submission checks completed at journal 19 Jan, 2026 First submitted to journal 12 Jan, 2026 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. 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14:26:18","extension":"html","order_by":10,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":75178,"visible":true,"origin":"","legend":"","description":"","filename":"earlyproof.html","url":"https://assets-eu.researchsquare.com/files/rs-8487176/v1/a09bc19085b9bed55e77fa82.html"},{"id":100898018,"identity":"f622cb3b-2ad2-4ec9-9dd4-4fcb49b75795","added_by":"auto","created_at":"2026-01-22 14:26:15","extension":"jpg","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":467140,"visible":true,"origin":"","legend":"\u003cp\u003eIndividual variation of the parapapillary choroidal dense pigmentation (PCP). The eyes without PCP have a high density of choroidal vessels and a low density of choroidal stroma (a). The eyes with circumferential PCP have a low density of choroidal vessels and a high density of choroidal stroma (b). Eye with temporal-PCP (c). Eye with circumferential PCP and black conus (d).\u003c/p\u003e","description":"","filename":"PCPFigure1.tif.jpg","url":"https://assets-eu.researchsquare.com/files/rs-8487176/v1/3c4dda95dbd535d2e6ea606d.jpg"},{"id":100898017,"identity":"56382285-20ff-4fe9-9bcc-5696132fd474","added_by":"auto","created_at":"2026-01-22 14:26:14","extension":"jpg","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":178811,"visible":true,"origin":"","legend":"\u003cp\u003eBox plot analysis of the differences between the groups. Differences in the axial length (a), optic disc tilt (b), and conus area (c) among the non-, temporal, and circumferential parapapillary choroidal dense pigmentation (PCP) groups are shown. The axial length and conus area were shorter and smaller, respectively, in the circum-PCP group than in the non-PCP group.\u003c/p\u003e","description":"","filename":"PCPFigure2.tif.jpg","url":"https://assets-eu.researchsquare.com/files/rs-8487176/v1/a854614aba77bd067baf025f.jpg"},{"id":100898051,"identity":"874df4d8-6c1f-4f51-84aa-a396f880ce21","added_by":"auto","created_at":"2026-01-22 14:26:27","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":1183526,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-8487176/v1/dd82f56a-d2a2-4ef5-bb01-e43c6fe6bea7.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"Parapapillary choroidal dense pigmentation in young healthy eyes: a cross-sectional study","fulltext":[{"header":"Background","content":"\u003cp\u003eHyper- and hypopigmentation around the optic nerve head was reported by Jonas et al. in 1988, and these were named parapapillary atrophy alpha (PPA alpha) [\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e, \u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e]. Irregular pigmentation, PPA alpha, was subsequently reported to be associated with relative scotoma [\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e] and more extensive in eyes with early glaucoma and ocular hypertension than in normal eyes [\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e, \u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e]. However, its frequency and size did not differ between the eyes with normal tension glaucoma and normal eyes [\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e]. A study reported that PPA alpha was detected in all 47 eyes with open-angle glaucoma, and its area was significantly correlated with the mean deviation of standard automated perimetry [\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eHistological examination of human eyes has revealed that PPA alpha is associated with thickening and thinning of the retinal pigment epithelium (RPE) [\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e]. Dichtl et al. reported that PPA alpha is located outside PPA beta and in a specific part of the RPE layer [\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e]. Furthermore, a long-term observational study in rhesus monkeys showed that the PPA beta increased in size, but the PPA alpha remained unchanged in size and frequency in a long-term observational study of rhesus monkeys [\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eA cross-sectional population study reported that the prevalence of zone alpha decreased by 0.4% per 10 years of age [\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e]. Jonas et al. reported an increase of approximately 0.6% in the PPA alpha area based on the findings of the Beijing study, which involved a 5-year follow-up. This increase was associated with older age and the coexistence of zone beta [\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eWe have been studying individual differences in the fundus of healthy young adults [\u003cspan additionalcitationids=\"CR14\" citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e]. We observed a ring-shaped pigmented band around the optic disc (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003eb) that was distinct from PPA alpha. This ring-shaped pigmented band is continuous with PPA alpha, as shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003eb. It appears black myopic conus in some eyes. Some eyes had a pigmented band around the entire optic disc, whereas others had it only on the temporal side (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003ec).\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eOn horizontal cross-sectional OCT image, there are no IS/OS line and thin RPE layer in the black myopic conus on the temporal side. And the IS/OS line is thin and RPE layer isn\u0026rsquo;t thick in the black area on the nasal side (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003ed). This suggests that the black area observed on the fundus photograph is attributable to a cause other than PPA alpha, which involves thickening of the RPE. The choroidal pigments are the only parts of the fundus structure that appear black, other than the RPE. Therefore, we named this pigment band observed in the fundus as the parapapillary choroidal dense pigmentation (PCP).\u003c/p\u003e \u003cp\u003eThis study investigated the relationships between the axial lengths, optic disc tilts, and conus areas of eyes with non-PCP, temporal-PCP, and circumferential-PCP.\u003c/p\u003e"},{"header":"Materials and methods","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e \u003ch2\u003eStudy design and study population\u003c/h2\u003e \u003cp\u003eThis prospective, cross-sectional observational study enrolled 133 participants. Only right eyes were included. Examinations were performed from November 2010 through February 2012. Individuals with no history of ocular disease were enrolled, based on a review of medical records and comprehensive ophthalmic examinations. The eligibility criteria were: ages of 20\u0026ndash;40 years; healthy eyes as determined by slit-lamp biomicroscopy, ophthalmoscopy, and optical coherence tomography (OCT); best-corrected visual acuity of \u0026ge;\u0026thinsp;0.1 logarithm of the minimum angle of resolution units; and intraocular pressure of \u0026le;\u0026thinsp;21 mmHg. The exclusion criteria were: eyes with ocular diseases such as glaucoma, pathologic myopia, and optic disc anomaly; known systemic diseases such as hypertension and diabetes; visual field defects; prior refractive or intraocular surgery; and poor OCT or fundus image quality. Eyes were excluded for the following reasons: glaucoma (n\u0026thinsp;=\u0026thinsp;1), superior segmental optic disc hypoplasia (n\u0026thinsp;=\u0026thinsp;3), and a history of refractive surgery (n\u0026thinsp;=\u0026thinsp;3). An additional nine eyes were omitted because fundus parameters could not be reliably evaluated. The data of 117 eyes (80 male and 37 female) were used for the analyses.\u003c/p\u003e \u003c/div\u003e\n\u003ch3\u003eMeasurements\u003c/h3\u003e\n\u003cp\u003eEach subject underwent a standardized set of ophthalmic examinations. These comprised slit-lamp biomicroscopy, fundus evaluation, intraocular pressure assessment with a pneumotonometer (CT-80; Topcon, Tokyo, Japan), and ultrasonic measurement of axial length (AL-2000; TOMEY, Nagoya, Japan). Objective refraction was obtained using an autorefractometer/keratometer (KR-8800; Topcon), and spherical equivalent values were used for analysis.\u003c/p\u003e \u003cp\u003eColor fundus photographs were obtained using the TRC-50LX (TOPCON, Tokyo, Japan). Color fundus photographs and the RNFL 3.4 mm circle scans were obtained using the Topcon 3D OCT-1000 Mark II (TOPCON, Tokyo, Japan). A Spectralis OCT device (Heidelberg Engineering, Germany) was used to obtain scanning laser ophthalmoscopy (SLO) images and cross-sectional views of the optic disc. The scan pattern was centered on the optic nerve head and comprised 73 horizontal B-scans spanning 15 degrees. The averages of the data of seven B-scans were obtained and used. Built-in image registration and eye-tracking functions were applied to minimize motion artifacts during image acquisition. Image quality was assessed by the operator, with confirmation of appropriate SD-OCT B-scan positioning within the image frame, proper centering on the optic nerve head, and an adequate quality score (\u0026gt;\u0026thinsp;20). The images were reacquired when necessary. The color fundus ophthalmoscopic and SLO fundus images were aligned using PowerPoint software based on the vascular pattern. The Spectralis OCT software was used to process and optimize SLO images, color fundus photographs, and cross-sectional OCT scans.\u003c/p\u003e\n\u003ch3\u003eAssessment of the PCP, conus area, and optic disc tilt\u003c/h3\u003e\n\u003cp\u003ePCP was assessed based on evaluation of color fundus photographs and cross-sectional images of the optic disc. The PCP was defined based on the presence of a dark black parapapillary circular pigment band on ophthalmoscopy and dense choroidal stroma with low choroidal vessel density on OCT. Eyes without these features were allocated to the non-PCP group (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003ea). Those with these features on the temporal side of the optic disc were allocated to the temporal-PCP group (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003ec), and those with these features on the circumference of the optic disc were allocated to the circum-PCP group (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003eb, d). The PCP and conus were independently assessed by two raters (KF and TY). The third rater (HT) determined the type of PCP in cases of disagreement.\u003c/p\u003e \u003cp\u003eOptic disc tilt was quantified according to a method previously reported by our group [\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e]. The optic disc tilt was quantified using the sine curve method based on the RNFL 3.4-mm circle scan, B-scan images obtained using the Topcon 3D OCT-1000 Mark II (TOPCON, Tokyo, Japan). The RPE course was plotted manually on the B-scan images. The coordinates of each pixel were determined automatically using ImageJ software. The coordinate system of the B-scan images was transformed such that the wave center served as the new origin. The converted data were fitted to the following sine wave equation using the curve fitting program of ImageJ:\u003cdiv id=\"Equa\" class=\"Equation\"\u003e\u003cdiv format=\"TEX\" class=\"mathdisplay\" id=\"FileID_Equa\" name=\"EquationSource\"\u003e\n$$\\:y=a\\times\\:\\text{sin}\\:(b\\times\\:x-c)$$\u003c/div\u003e\u003c/div\u003e\u003c/p\u003e \u003cp\u003eThe amplitude (a) of the sine curve was defined as the degree of optic disc tilt. The conus area was measured from the fundus photographs using ImageJ. The image size decreases with increasing axial length because the fundus is farther from the camera. The magnification effect of the axial length was adjusted using Bennett\u0026rsquo;s formula (3.12 \u0026times; 0.01306 \u0026times; 100%/mm) [\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e, \u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e].\u003c/p\u003e\n\u003ch3\u003eStatistical analyses\u003c/h3\u003e\n\u003cp\u003eThe intra-rater agreement for the PCP was determined using the weighted Cohen\u0026rsquo;s kappa coefficient. The Kruskal\u0026ndash;Wallis one-way analysis of variance and Steel\u0026ndash;Dwass multiple comparison tests were used to determine the significance of the differences in the axial length, conus area, and optic disc tilt among the groups. Statistical analyses were performed using R (version 3.0.2; The R Foundation for Statistical Computing, Vienna, Austria). Statistical significance was set at p\u0026thinsp;\u0026lt;\u0026thinsp;0.05.\u003c/p\u003e\n\u003ch3\u003eEthics\u003c/h3\u003e\n\u003cp\u003e This study was approved by the Ethics Committee of Kagoshima University Hospital (registration number:22\u0026ndash;72) on September 30, 2010. All the procedures conformed to the tenets of the Declaration of Helsinki. We obtained written informed consent from all participants after explaining the procedures.\u003c/p\u003e"},{"header":"Results","content":"\u003cp\u003eThe demographic information of the patients is provided in Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e. The mean age and axial length of the patients were 25.8 years and 25.5 mm, respectively. The number of eyes without PCP, with temporal-PCP, and with circum-PCP were 49, 17, and 51, respectively. The inter-rater agreement for PCP was high (kappa\u0026thinsp;=\u0026thinsp;0.81). The axial length of the circum-PCP group was significantly shorter than that of the non-PCP group (p\u0026thinsp;=\u0026thinsp;0.011). However, the differences between the non-PCP and temporal-PCP groups (p\u0026thinsp;=\u0026thinsp;0.914) and between the temporal-PCP and circum-PCP groups (p\u0026thinsp;=\u0026thinsp;0.195) were not significant (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003ea). The optic disc tilt did not significantly differ among the three groups (non vs. temporal, p\u0026thinsp;=\u0026thinsp;0.061; temporal vs. circum, p\u0026thinsp;=\u0026thinsp;0.729; non vs. circum, p\u0026thinsp;=\u0026thinsp;0.108) (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003eb). The conus area was significantly smaller for the circum-PCP group than for the non-PCP group (p\u0026thinsp;=\u0026thinsp;0.047). However, the differences between the non-PCP and temporal-PCP groups (p\u0026thinsp;=\u0026thinsp;0.908) and between the temporal-PCP and circum-PCP groups (p\u0026thinsp;=\u0026thinsp;0.351) were not significant (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003ec).\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\u003eParticipant characteristics\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"3\"\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 \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eMean\u0026thinsp;\u0026plusmn;\u0026thinsp;standard deviation or\u003c/p\u003e \u003cp\u003eMedian (interquartile range)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eRange\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\u003e25.8\u0026thinsp;\u0026plusmn;\u0026thinsp;4.0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e22\u0026ndash;40\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eSex (male/female)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e80 / 37\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eSpherical equivalent (diopters)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e-4.72\u0026thinsp;\u0026plusmn;\u0026thinsp;3.33\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e-14.25-0.50\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eAxial length (mm)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e25.45\u0026thinsp;\u0026plusmn;\u0026thinsp;1.42\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e22.43\u0026ndash;30.42\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003ePCP (non/temporal/circum)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e49 / 17 / 51\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eOptic disc tilt (pixels)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e37.69\u0026thinsp;\u0026plusmn;\u0026thinsp;17.19\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e8.80\u0026ndash;80.77\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eConus area (pixels)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e377.79 (0.00, 794.06)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0.00\u0026ndash;4194.98\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003ctfoot\u003e \u003ctr\u003e\u003ctd colspan=\"3\"\u003ePCP: parapapillary choroidal dense pigmentation\u003c/td\u003e\u003c/tr\u003e \u003c/tfoot\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003e \u003c/p\u003e"},{"header":"Discussion","content":"\u003cp\u003eThis study presents the first characterization of PCP, a new morphological feature in young healthy eyes. We found a significant association between the circumferential PCP pattern and shorter axial length and smaller conus area. These results suggest that PCP may be a feature of less ocular elongation, distinguishing it from established myopic changes, and requires further investigation into its choroidal origin.\u003c/p\u003e \u003cp\u003eThe axial length and conus area were shorter and smaller, respectively, for the circum-PCP group than in the non-PCP group. These results suggest that circum-PCP may be one of the hyperopic features. Myopic features [\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e] include myopic conus (PPA beta, gamma, and delta zones) [\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e], optic disc tilt [\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e], tessellation [\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e], vessel shift toward the fovea [\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e], and peripapillary nerve fiber elevation [\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e]. However, a few special hyperopic features have been reported in the fundus. Hyperopia is a refractive state of an eye with less eyeball elongation during growth [\u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e, \u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e]. The choroid is very thick during infancy, but it gradually thins as the eyeball expands during growth [\u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e]. This is easy to understand if you imagine a balloon inflating. For example, the area around the inlet of the green balloon is darker than the rest of the balloon. The morphology is similar when the optic disc is considered the inlet of the eyeball, with a ring-shaped area of concentrated choroidal pigment around the optic disc. A short axis and small conus suggest less bulging of the eyeball. The choroidal pigment remains dark around the disc in such eyes, creating a ring-shaped black area that may result in PCP.\u003c/p\u003e \u003cp\u003eThe inlet of the balloon appears darker due to its weak inflation and thick wall. Which is the greater factor in PCP? The choroid in the PCP area appears to be rich in stromal components rather than thick, as observed in the OCT images (Figs.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003eb\u0026ndash;d). The choroidal vascular component is abundant up to the optic disc in eyes without PCP (such as those in Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003ea), but the stromal component is scant. The proportions of the stromal components in the choroid vary greatly among individuals [\u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e, \u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e]. The stromal and vascular components become thinner as axial length increases [\u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e, \u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e]. This results in the visibility of the large choroidal vessels, which causes stronger tessellation and a redder fundus [\u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e25\u003c/span\u003e]. PPA alpha was present in 98.6% of the cases in an epidemiological study involving Indians [\u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e26\u003c/span\u003e]. This study focused on Japanese participants, whose fundus pigmentation is darker than that of Westerners. PCP may be present in eyes with dark fundus pigmentation and weak ocular dilation due to individual and racial differences. Further research is needed to investigate the relationship between the ratio of choroidal stromal and vascular components [\u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e] and PCP in various ethnic groups.\u003c/p\u003e \u003cp\u003eThe axial length of the non-PCP group was longer than that of the circum-PCP group. This suggests that myopic fundus changes attenuate PCP. The conus area was larger for the group without PCP than for the group with PCP. Axial elongation causes the choroid to become paper-thin on the temporal side of the optic disc, the sclera becomes visible, resulting in a whitish myopic conus [\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e]. The nerve fibers on the nasal side of the optic disc are elevated and appear whitish in eyes with peripapillary nerve fiber elevation [\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e]. This may reduce the visibility of the choroid and the apparent blackness of the fundus. Optic disc tilt is also a myopic change, and we expected the circum-PCP group to have greater optic disc tilt than the non-PCP group. However, the difference was not significant. This suggests that optic disc tilt has less effect on PCP than axial length and conus area. Further research is needed to investigate the relationship between myopic changes associated with axial elongation during growth and changes in PCP.\u003c/p\u003e \u003cp\u003eThe PPA alpha reported by Jonas et al. [\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e, \u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e] may be influenced by RPE irregularity on the temporal side of the optic disc. However, the fundus findings in Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e show a black ring around the optic disc that is connected to PPA alpha. Therefore, RPE irregularity around the optic disc is unlikely. Moreover, the term PPA is inappropriate because PCP is not an atrophic change. PCP is a fundus finding derived from choroidal pigment and must be distinguished from the RPE irregularity.\u003c/p\u003e \u003cp\u003eThis study has some limitations. First, it was a cross-sectional correlation study, and the chronological changes in PCP could not be observed. Second, it involved a young Japanese population. An epidemiological study showed that the Japanese population was the most myopic [\u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e27\u003c/span\u003e]. PCP may be common in young healthy eyes, but the findings of this study may not be generalizable to other ethnic groups.\u003c/p\u003e"},{"header":"Conclusions","content":"\u003cp\u003eThis study reports PCP, a fundus finding related to choroidal pigment around the optic disc. PCP may be observed in hyperopic eyes and may serve as an indicator of individual differences in fundus pigment. However, many aspects of PCP remain unclear, and further research is needed to explore ethnic differences, its relationship with quantified choroidal structure, and its association with ocular diseases.\u003c/p\u003e"},{"header":"Abbreviations","content":"\u003cp\u003eOCT, ocular coherence tomography\u003c/p\u003e\n\u003cp\u003ePCP, parapapillary choroidal dense pigmentation\u003c/p\u003e\n\u003cp\u003ePPA alpha, parapapillary atrophy alpha\u003c/p\u003e\n\u003cp\u003eRPE, retinal pigment epithelium\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eEthics approval and consent to participate\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThis study was approved by the Ethics Committee of Kagoshima University Hospital and registered with the University Hospital Medical Network Clinical Trials Registry (registration number: UMIN000007154). All the procedures conformed to the tenets of the Declaration of Helsinki. We obtained written informed consent from all participants after explaining the procedures.\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\u003eThe datasets used and/or analyzed during the current study are available from the corresponding author on reasonable request.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eCompeting interests\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe authors have no conflicts of interest. The authors have no financial disclosures.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eFunding\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThis work was supported in part by JSPS KAKENHI grant 15H04996 and 25K12838. The funders had no role in the study design, data collection and analysis, decision to publish, or manuscript preparation.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAuthors' contributions\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eConceptualization and Methodology, T.Y. and A.I.; Data Curation, T.Y. and K.N.; Formal Analysis, T.Y. and Y.U.; Writing – Original Draft Preparation, T.Y. and Y.U.; Writing – Review \u0026amp; Editing, H.T., A.I. and T.S.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAcknowledgements\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eWe want to thank Editage (www.editage.jp) for English language editing.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAuthors' information (optional)\u003c/strong\u003e\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\u003cli\u003e\u003cspan\u003eJonas JB, Gusek GC, Naumann GO. Die parapapill\u0026auml;re Region in Normal- und Glaukomaugen. I. 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Longitudinal changes in choroidal thickness varied with refractive progression in myopic and non-myopic children: A two-year cohort study. Invest Ophthalmol Vis Sci. 2024;65:17.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eIto Y, Endo H, Kase S, Takahashi M, Sonoda S, Sakoguchi T, et al. Effects of age and axial length on choroidal stratified structure in normal eyes. Sci Rep. 2024;14:2527.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eSuwan Y, Chansangpetch S, Fard MA, Pooprasert P, Chalardsakul K, Threetong T, et al. Association of myopia and parapapillary choroidal microvascular density in primary open-angle glaucoma. PLoS ONE. 2025;20:e0317881.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eYoshihara N, Yamashita T, Ohno-Matsui K, Sakamoto T. Objective analyses of tessellated fundi and significant correlation between degree of tessellation and choroidal thickness in healthy eyes. PLoS ONE. 2014;9:e103586.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eJonas JB, Thomas R, George R, Berenshtein E, Muliyil J. Optic disc morphology in south India: the Vellore Eye Study. Br J Ophthalmol. 2003;87:189\u0026ndash;96.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eSawada A, Tomidokoro A, Araie M, Iwase A, Yamamoto T, Tajimi Study Group. Refractive errors in an elderly Japanese population: the Tajimi study. Ophthalmology. 2008;115:363\u0026ndash;e3703.\u003c/span\u003e\u003c/li\u003e\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":"international-journal-of-retina-and-vitreous","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"IJRV","sideBox":"Learn more about [International Journal of Retina and Vitreous](https://jneurodevdisorders.biomedcentral.com/)","snPcode":"40942","submissionUrl":"https://submission.nature.com/new-submission/40942/3","title":"International Journal of Retina and Vitreous","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"stoa","reportingPortfolio":"BMC/SO AJ","inReviewEnabled":true,"inReviewRevisionsEnabled":true},"keywords":"parapapillary choroidal dense pigmentation, pigmented conus, axial length","lastPublishedDoi":"10.21203/rs.3.rs-8487176/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-8487176/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003ch2\u003eBackground\u003c/h2\u003e \u003cp\u003eSome eyes with parapapillary choroidal dense pigmentation (PCP) have a pigmented conus visible on color fundus photography. This study aimed to determine the prevalence of PCP in young healthy eyes and examine its relationships with axial length, optic disc tilt, and conus area.\u003c/p\u003e\u003ch2\u003eMethods\u003c/h2\u003e \u003cp\u003eThis prospective, observational, cross-sectional study included the right eyes of 133 participants, who were examined between November 1, 2010 and February 20, 2012. Among them, 117 right eyes of 117 patients were finally analyzed. Participants underwent comprehensive ophthalmologic examinations, including axial length measurement, fundus photography, and optic disc optical coherence tomography (OCT). Based on their color fundus photographs and optic disc cross-sectional OCT images, eyes were categorized into the non-PCP, temporal-PCP, and circum-PCP groups. Optic disc tilt was evaluated using a sine curve based on the retinal nerve fiber layer B-scan images. The conus area in the color fundus images was calculated using ImageJ and corrected using Bennett's formula. The Steel\u0026ndash;Dwass test was used to perform multiple comparisons of the axial length, optic disc tilt, and conus area among the three groups.\u003c/p\u003e\u003ch2\u003eResults\u003c/h2\u003e \u003cp\u003eThe mean age and axial length of the participants were 25.8 years and 25.5 mm, respectively. Of the 117 eyes, 49, 17, and 51 had non-PCP, temporal-PCP, and circum-PCP, respectively. The axial length (p\u0026thinsp;=\u0026thinsp;0.011) and conus area (p\u0026thinsp;=\u0026thinsp;0.047) were shorter and smaller, respectively, for the circum-PCP group than for the non-PCP group. No significant differences were observed in the other intergroup comparisons.\u003c/p\u003e\u003ch2\u003eConclusions\u003c/h2\u003e \u003cp\u003eThe eyes with circumferential PCP had shorter axial lengths and smaller conus areas than those without.\u003c/p\u003e","manuscriptTitle":"Parapapillary choroidal dense pigmentation in young healthy eyes: a cross-sectional study","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2026-01-22 14:24:00","doi":"10.21203/rs.3.rs-8487176/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"decision","content":"Revision requested","date":"2026-03-30T09:19:54+00:00","index":"","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2026-03-28T23:00:41+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"89211922637056700780773787338668066124","date":"2026-03-19T11:53:14+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"258685912771681799719933328842468446339","date":"2026-03-18T07:20:01+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"240106398866528508614931610837743351848","date":"2026-03-01T07:19:59+00:00","index":"hide","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2026-02-07T21:35:48+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"334628551743726060447615484420566138545","date":"2026-02-01T12:46:33+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"146356072132608355002173392394336956531","date":"2026-01-26T09:27:31+00:00","index":"hide","fulltext":""},{"type":"reviewersInvited","content":"","date":"2026-01-21T07:56:11+00:00","index":"","fulltext":""},{"type":"checksComplete","content":"","date":"2026-01-19T17:27:10+00:00","index":"","fulltext":""},{"type":"submitted","content":"International Journal of Retina and Vitreous","date":"2026-01-13T03:18:43+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"international-journal-of-retina-and-vitreous","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"IJRV","sideBox":"Learn more about [International Journal of Retina and Vitreous](https://jneurodevdisorders.biomedcentral.com/)","snPcode":"40942","submissionUrl":"https://submission.nature.com/new-submission/40942/3","title":"International Journal of Retina and Vitreous","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"stoa","reportingPortfolio":"BMC/SO AJ","inReviewEnabled":true,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"84852978-52d1-4c93-9426-20a4921181b6","owner":[],"postedDate":"January 22nd, 2026","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"under-review","subjectAreas":[],"tags":[],"updatedAt":"2026-04-25T09:24:13+00:00","versionOfRecord":[],"versionCreatedAt":"2026-01-22 14:24:00","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-8487176","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-8487176","identity":"rs-8487176","version":["v1"]},"buildId":"XKTyCvWXoU3ODBz1xrDgd","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}