Optic Pathway Measurements on MRI: Normal Values in the Pediatric Population

Optic Pathway Measurements on MRI: Normal Values in the Pediatric Population | 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 Optic Pathway Measurements on MRI: Normal Values in the Pediatric Population Nermeen El Sebaie, Hanan Morsi, Ahmed Abdelzaher, Ahmed El-Beheiry This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-9253327/v1 This work is licensed under a CC BY 4.0 License Status: Posted Version 1 posted You are reading this latest preprint version Abstract Background Different pathologies can affect the optic pathway structures in children, and early detection of these pathologies requires knowledge of their normal measurements. Our study aimed to establish a standardised method for measuring the optic pathway structures and report their normal values in children up to six years of age using brain MRI. Methods We retrospectively analysed the brain MR images of pediatric patients from infants to six years of age; scans that were interpreted as normal were included in the study. Axial T2-weighted images were used for optic nerve (intraorbital, pre-chiasmatic) and optic tract measurements. Coronal T2-weighted images were used for optic chiasm measurements. Patients were stratified into six age groups for analysis. Results A total of 104 MRI studies of the brain were included; there were 65 males and 39 females. The mean age of all the patients was 26 ± 12 months. An increase in diameter was observed with age for all measurements. There is a strong positive correlation between age and mean diameter of each of the intraorbital optic nerve (r = 0.670), pre-chiasmatic optic nerve (r = 0.703), optic tract (r = 0.693), as well as the height of the optic chiasm (r = 0.716). Conclusions Using axial and coronal brain MRI, we suggested standardised locations for measuring the optic pathway structures and reported their normal values in children from birth to 6 years of age. optic nerve optic chiasm optic tract optic pathway normal measurments Figures Figure 1 Figure 2 Figure 3 Introduction Early diagnosis of optic pathway disorders in the pediatric population is important as many disease entities can be seen affecting the optic pathway, such as hypoplasia, atrophy, inflammation, demyelinating, and neoplasia [ 1 ]. These pathologies can result in an increase or decrease in the diameter of different optic pathway structures. Although subjective evaluation can detect diseases affecting the visual pathway, objective measurements are more valuable for timely diagnosis [ 2 ]. Optic nerve hypoplasia (ONH) is the most common congenital optic disc anomaly. It is a non-progressive condition that can be isolated or associated with abnormalities of the pituitary gland and brain [ 3 ]. Patients may present with poor vision, nystagmus, neurologic symptoms, or endocrine dysfunction [ 4 , 5 ]. Measuring different segments of the optic pathway can be a critical tool for the diagnosis of ONH; however, accurate imaging assessment requires knowledge of the normal dimensions of these structures. While different diagnostic modalities can study the disc portion of the optic nerve, MR imaging is superior due to its ability to visualise the whole optic pathway with high soft-tissue resolution [ 6 ]. Limited literature is available regarding the normal size of the intraorbital and intracranial optic nerve as well as the optic chiasm and optic tract in children, and a sufficient number of normative data are still lacking. Our study aimed to establish a standardised method for measuring the optic pathway on MRI in the pediatric population, particularly in the early years and to report normal values of the optic pathway structures in pediatric patients up to 6 years of age using normal brain MRIs. Patients and Methods This was a retrospective study carried out by the Department of Diagnostic and Interventional Radiology of our institution. The study was approved by the institutional review board, and informed consent was waived. Patient selection The study took place over a period from January 2020 through May 2024. We retrospectively analysed the brain MR images of pediatric patients from infants to 6 years of age, who presented to our institution with symptoms or signs that are likely not related to involvement of the visual pathway, such as epilepsy, mild head trauma, ear pathologies or headache. Scans that were interpreted as normal by one of two neuroradiologists (NE, AA) with 8 and 15 years of experience, respectively, were included in the study. Exclusion criteria consisted of a history of prematurity (< 34 weeks), brain or ocular surgery, and MRI findings of cerebral ischemia, haemorrhage, atrophy or increased intracranial pressure. MRI studies that were degraded by motion or with poor visualisation of the optic nerve were also excluded. The exclusion flowchart is shown in Fig. 1 . Magnetic resonance imaging and measurements MRI scans were obtained on a 1.5T scanner (SOMATOM Definition Edge, Siemens, Germany) using a 16-channel head coil. Axial T2-weighted turbo spin echo images of the brain were used for optic nerve (intraorbital, pre-chiasmatic) and optic tract measurements. A Coronal T2-weighted turbo spin echo images, angled perpendicular to the long axis of the hippocampal body, were used for optic chiasm measurements. This sequence was routinely obtained in patients presenting with epilepsy. Acquisition parameters were as follows: repetition time (TR): 3,000–6,000 ms, echo time (TE): 80– 131 ms, section thickness 3 mm, intersection gap 0 mm, field of view 210 mm, and matrix 256×256. Measurements A total of seven measurements were performed for each patient, consisting of three bilateral measurements (intraorbital optic nerve, pre-chiasmatic optic nerve and optic tract), and one measurement in the midline (median height of the chiasm), as shown in Fig. 2 . Bilateral measurements of the transverse diameter of the intraorbital optic nerve were performed perpendicular to the longitudinal axis of the optic nerve at 3 mm behind the globe without including the optic nerve sheath (Fig. 2 A). The width of the pre-chiasmatic optic nerve was obtained at its mid-segment, approximately 5 mm posterior to the optic canal (Fig. 2 B). Measurements of each optic tract diameter were performed at the level of the anterior border of the cerebral peduncle (Fig. 2 C). If the measurement could not be performed within 1–2 mm of the intended location, or if the discrete margins of the nerve were not clearly visualized; the nerve was considered not measurable. The measurement of the optic chiasm was obtained on coronal sections at the slice where the maximum transverse diameter of the chiasm was visualized, and the central height of the chiasm was measured exactly at the midline perpendicular to the longitudinal axis of the chiasm (Fig. 2 D). The measurements were recorded into six groups, stratified by the patient’s age on the day of the MRI scan: Group I, 0 to 6 months; Group II, 6m to 1y; Group III, 1 to 2 years; Group IV, 2 to 3 years; Group V, 3 to 4 years and group VI, 4 to 6 years. All measurements were obtained using the built-in digital caliper tool in our Picture Archiving and Communication System (PACS). In some cases, measurements were performed on one side; if the other side was not delineated. Measurements were obtained by two neuroradiologists (NE, AA). The measurements of the two readers were used to calculate the inter-observer reproducibility. The average of the two measurements was used for the statistical analysis. Statistics Data analysis was performed by SPSS software, version 25 (SPSS Inc., PASW statistics for windows version 25. Chicago: SPSS Inc.). Data normality was assessed using Kolmogrov-Smirnov test. Differences between the right and left sides and between males and females were evaluated using the Student t test. There was neither side nor sex differences, so bilateral variables were averaged across the two sides. The mean values and standard deviations (SD) of the intraorbital optic nerve, pre-chiasmatic optic nerve, optic chiasm and optic tract diameters were calculated and stratified by each age group. Statistical differences of the mean values among each age group were analysed by using One Way ANOVA test with Post Hoc Tukey test to detect pair-wise comparison. Finally, measurement results were plotted versus age, and Pearson correlation coefficient was calculated. Intraclass correlation coefficients (ICC) with 95% confidence intervals were used to evaluate the interobserver reproducibility of the measurements. Inter-observer agreement was defined as excellent (≥ 0.81), good (0.61–0.80), moderate (0.41–0.60), fair (0.21–0.40), and poor (≤ 20). Results A total of 104 MRI studies of the brain were included, there were 65 males and 39 females. The mean age of all the patients was 27 ± 19 months (age range: 2–66 months). Optic nerve (intraorbital and pre-chiasmatic), and optic tract measurements did not differ between the right and left sides or between males and females. Interobserver agreement was excellent, with an intraclass correlation coefficient of 0.845 (95% CI, 0.819–0.836; P, .001), 0.881 (95% CI, 0.871–0.888; P, .001), 0.860 (95% CI, 0.840–0.873; P, .001) and 0.981 (95% CI, 0.971–0.988; P, .001), for the introrbital optic nerve, pre-chiasmatic nerve, optic tract and optic chiasm respectively. Axial imaging revealed a steady age-related increase in the mean diameter of the intraorbital optic nerve, from 1.90 ± 0.11 mm in infants under 6 months to 2.64 ± 0.14 mm in children aged 4–6 years. Similarly, the pre-chiasmatic optic nerve diameter increased from 2.73 ± 0.07 mm in the youngest group to 3.62 ± 0.15 mm in the 4–6-year cohort. The optic tract also exhibited progressive growth, with mean diameters rising from 1.82 ± 0.09 mm (under 6 months) to 2.54 ± 0.11 mm (4–6 years). Optic chiasm measurements were available only in 46 pediatric patients with epilepsy. The central height of the optic chiasm measured 1.23 ± 0.07 mm in infants ≤ 6 months and increased to 1.74 ± 0.05 mm in the 4–6-year age group. Differences between age groups were evaluated for each measurement, a significant difference was observed for most of the measurements with an overlap observed between group III and IV for intraorbital optic and pre-chiasmatic and optic tract measurements, and between group II and III for pre-chiasmatic and optic tract measurements. There was a significant difference in optic chiasm measurements between group I and II. An overlap was observed between group III and IV as well as between group V and VI. The number of cases, mean diameter of the optic pathway structures stratified by age group, and details of comparison between groups are shown in Table 1 . The results were plotted in a measurement-versus-age comparison. The graphs show that there is a strong positive correlation between age and mean diameter of each of the intraorbital optic nerve (r = 0.670, p < .001), pre-chiasmatic optic nerve (r = 0.703, p < .001), optic tract (r = 0.693, p < .001) as well as the height of the optic chiasm (r = 0.716, p < .001) (Fig. 3 ). Table 1 Number of measured optic nerves, optic chiasm and optic tracts, mean diameters and standard deviation (SD) stratified by age groups Age group Number of cases Intraorbital optic nerve Pre-chiasmatic optic nerve Optic tract Optic chiasm n mean ± SD n mean ± SD n Mean ± SD n mean ± SD 0–6 16 32 1.90 ± 0.11 27 2.73 ± 0.07 30 1.82 ± 0.09 9 1.23 ± 0.07 6 m- 1year 16 30 2.16 ± 0.08 29 2.99 ± 0.12 A 28 1.99 ± 0.10 A 10 1.40 ± 0.12 1–2 year 17 34 2.27 ± 0.095 A 31 3.10 ± 0.18 AB 33 2.09 ± 0.15 A 8 1.60 ± 0.09 A 2–3 year 20 40 2.33 ± 0.18 A 34 3.22 ± 0.24 B 39 2.24 ± 0.17 7 1.58 ± 0.11 A 3–4 year 15 30 2.48 ± 0.15 24 3.42 ± 0.18 30 2.36 ± 0.10 8 1.70 ± 0.05 B 4–6 year 20 40 2.64 ± 0.14 36 3.62 ± 0.15 40 2.54 ± 0.11 14 1.74 ± 0.05 B P value* 104 < 0.001 < 0.001 < 0.001 < 0.001 * P value using One Way ANOVA test to assess the significance of the between-group comparisons, A and b Similar letters in same row denote non-significant difference between these age groups by post hoc Tukey test Discussion In this study, we analysed the diameters of the optic pathway, including the width of the intraorbital, pre-chiasmatic optic nerve and the optic tract, as well as the height of the optic chiasm in pediatric patients from 0 to 6 years old on T2-weighted MR images of the brain. Our results showed that all structures increased with age, with significant differences between age groups in all measurements, independent of sex or eye laterality. In our study, the mean diameter of the intraorbital optic nerve in children up to 6 months of age measured at 3 mm behind the globe was 1.90 ± 0.11 mm. Our measurements were slightly greater than those reported by Al-Haddad et al. [ 7 ] who found that the intraorbital optic nerve diameter in the same age group was 1.53 ± 0.82 mm. The authors of this study used axial STIR images of the orbit at a 2–3 mm section thickness, which could explain this difference. Janthami et al. [ 8 ] focused on measuring the intraorbital optic nerve in the first 4 years of age and stratified them into 4 age groups. They used routine brain sections as in our study; however, our measurements for the intraorbital optic nerve were smaller than the measurements in this study for all age groups (Table 2 ). This could be explained by the greater section thickness they used (4–6 mm), in comparison with our study as routine axial T2-weighted images of the brain for pediatric patients in our institution were obtained with 3 mm thickness. At the age group from 2 years up to 6 years in our study, the mean diameter of the intraorbital optic nerve increased from 2.17 ± 0.21 mm in children up to 3 years, to 2.57 ± 0.17 mm in the age group from 4–6 years. Markat et al. [ 9 ] reported that the mean axial diameter of the retrobulbar optic nerve was 2.99 ± 0.29 mm at the age group ranging from 4–6 years. Table 2 Diameters of the intraorbital optic nerve measured axially 3 mm behind the globe in different studies Intraorbital optic nerve measured axially 3 mm behind the globe (retrobulbar) Age group Alhaddad et al. 1 Our study 2 Age group Markat et al. 3 Our study Age group Janthami et al. 4 Our study < 6 months 1.53 ± 0.82 1.90 ± 0.11 0–3 years 2.86 ± 0.31 2.17 ± 0.21 0–1 year 2.3 ± 0.4 2.02 ± 0.17 6m to 2 years 2.03 ± 0.30 2.22 ± 0.10 4–6 years 2.99 ± 0.29 2.57 ± 0.17 1–2 years 2.6 ± 0.2 2.27 ± 0.09 2–6 years 2.20 ± 0.30 2.48 ± 0.21 2–3 years 2.4 ± 0.3 2.33 ± 0.18 3–4 years 2.9 ± 0.4 2.48 ± 0.15 1 Using axial short time inversion recovery (STIR) sequence of the orbit with 2 to 3 mm section thickness; 2 Axial T2-weighted turbo spin echo images of the brain 3 mm section thickness; 3 using high-resolution 3dimensional T2-weighted fast spin echoo MR sequence 0.5 to 0.6 mm section thickness; 4 using axial T2-weighted turbo spin echo image of the brain 4 to 6 mm section thickness. Demonstrated from the previous comparison, there are some differences between measurements of the intraorbital optic nerve in the same age group with different acquisition sequences and different slice thickness. The optic pathway in children consists of small structures, which can make accurate and reproducible measurements challenging. Similar to previous studies [ 8 , 10 ], we used an axial T2-weighted turbo spin echo sequence of the brain for different optic pathway measurements. We believe that this is a more practical way to assess the optic pathway, and it is the technique that most neuroradiologists would adopt to make their diagnosis. Methods adopted in other studies [ 7 , 9 ] typically involved dedicated orbital MRI fat-saturated acquisition sequences along the axis of the optic nerve in addition to the commonly acquired sequences and extended the scan time for each patient. It can also involve imaging post-processing procedures, rendering it difficult to implement in routine clinical work. Furthermore, an additional thin slice thickness sequence on the MRI in pediatric patients means adding more time on the scanner and more time in sedation [ 11 ]. In the setting of suspected optic nerve hypoplasia, assessment of optic nerve size is mostly done as part of the evaluation of other structural brain abnormalities. Markat et al. [ 9 ] found a strong inter-reader agreement for the measurement of the intracranial segment of the optic nerve. They recorded that the width of the pre-chiasmatic optic nerve at its mid portion was 3.75 ± 0.28 mm at the age group of 4–6 years, which is similar to our results at the same age group (3.62 ± 0.15 mm). For optic tract measurements, the mean diameter among patients younger than 6 months was 1.82 ± 0.09 mm. Oyama et al. found that the mean of the width of the optic tract was 1.5 ± 0.1 mm in neonates with no intracranial abnormalities at term-equivalent age. AS each component of the optic pathway grows at proportional rates, measurement of the optic pathway can be obtained at any point, and a suspicion for the presence of ONH can still be raised [ 12 ]. ONH is the most common congenital optic disc anomaly. The diagnosis of ONH is done by ophthalmoscopic confirmation of a small optic disc, often in combination with fundus photography [ 13 ]. Fundus photography overcomes problems with optic disc visualisation and can provide a measurement of the optic disc size that cannot be obtained by ophthalmoscopic examination. However, fundus photography in children is difficult in the presence of nystagmus or high refractive errors, which occur frequently in patients with ONH [ 13 ]. Kruglyakova J et al. [ 12 ] performed MRI in addition to fundus photography in children with suspected ONH before 2 years of age. Using fundus photographs, the ratio of the horizontal disc diameter (DD) to the distance between the macular and the temporal edge of the disc (DM) was measured, and the DD/DM ratio of optic nerves with normal vision was estimated to be greater than 0.35. They reported that all eyes with a DD/DM ratio of optic nerves less than 0.35 had an optic nerve diameter < 1.7 mm on MRI and diagnosed as having ONH, suggesting that optic nerve diameter < 1.7 mm is 100% sensitive for the diagnosis of ONH [ 12 ]. The minimum width of the intra-orbital optic nerve measured in our study was 1.8 mm. Neuroimaging in patients with the diagnosis of ONH is essential due to the high association with brain and pituitary abnormalities. The most prevalent neuroimaging findings included abnormalities of the corpus callosum, septum pellucidum and pituitary gland, including absent or ectopic posterior pituitary bright spot and infundibular hypoplasia [ 14 – 16 ]. All patients with a pituitary gland malformation on imaging develop hypothalamic-pituitary dysfunction. It is noteworthy that 66% of patients with a normal pituitary gland on MRI can also develop hypothalamic-pituitary dysfunction [ 16 – 20 ]. The presence of ONH alone is a risk factor for the development of hypothalamic-pituitary dysfunction, independent of the presence of various anatomic abnormalities of the brain. Other reported neuroimaging abnormalities included schizencephaly, arachnoid cysts, pachygyria, polymicrogyria, cortical heterotopia, white matter hypoplasia, and hydrocephalus [ 20 – 22 ]. Jeunger et al. [ 11 ] assessed optic chiasm height using a standard 3D T1-weighted MRI sequence and reported that measuring optic chiasm dimensions is easier and more reproducible than intraorbital optic nerve measurements. The optic chiasm is a rather fixed structure and less vulnerable to motion artefacts compared to orbital optic nerve measurement, less variable in morphology, bigger in dimensions and, thus, a simple target for MR investigations. However, the coronal plane should be perpendicular to the optic chiasm; otherwise, measurements at varying angles to the course of the optic chiasm will result in higher values and variance [ 23 ]. A few limitations must be brought to attention regarding this study. We didn’t use coronal sections for measuring the intraorbital optic nerve because routine brain MR images were not obtained perpendicular to the axis of each optic nerve. Since none of the patients exhibited overt visual symptoms or signs, direct comparison with a reference standard (e.g., ophthalmoscopic findings) was not possible. Conclusions It is important to define standardized locations along the course of the optic pathway for accurate assessment. We measured the width of the intraorbital optic nerve 3 mm behind the globe, the pre-chiasmatic optic nerve at its mid segment, and the optic tract at the anterior border of the brain stem on axial T2-weighted images. On coronal T2-weighted images acquired perpendicular to the optic chiasm; we measured the central height of the chiasm. We reported normal measurements of the optic pathway structures, providing reference values in children from birth to 6 years of age using routine brain MRI. Declarations Acknowledgements Not applicable Ethics approval and consent to participate Approval for this study was obtained from the Research Ethics Committee of Faculty of Medicine, Alexandria University (IRB NO: 00012098; FWA NO: 00018699; Serial NO: 0306769). All study procedures were carried out in accordance with the Declaration of Helsinki regarding research involving human subjects. Consent to participate was waived (retrospective study). Consent for publication Not applicable. Availability of data and material The datasets used and analyzed during the current study are available from the corresponding author on reasonable request. Competing interests The authors declare that they have no competing interests. Funding None (authors personal contribution). References Kanda T, Miyazaki A, Zeng F, et al (2020) Magnetic resonance imaging of intraocular optic nerve disorders: Review article. 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Clin Ophthalmol 13:2607–2616 Braga N, Pareto D, Mongay-Ochoa N, et al (2024) optic chiasm manual and automated measurments in sub-acute optic neuritis with OCT and MRI correlations. Eur J Radiol 172:111332. Additional Declarations No competing interests reported. Cite Share Download PDF Status: Posted Version 1 posted 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-9253327","acceptedTermsAndConditions":true,"allowDirectSubmit":true,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":617056287,"identity":"8885fb46-e57c-448a-b47b-e62b026c7ab6","order_by":0,"name":"Nermeen El Sebaie","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAA5klEQVRIiWNgGAWjYNCDigoGBgPStJw5Q7KWs21EaDFn73264UPFnWh+6faHDw7OOyxvzt58gOFHxTacWix7jpvdnHHmWe7MOWeMDQ5uO2y4s+dYAmPPmds4tRjcSGO7zdt2OHfDjRw26Y/bDjMCGQbMjG14tNx/xnb77z+QlvTnPw7OOWxPWMsNNrbbjA0gLQlmDAcbDicS1nImje1mz7HDuTNn5BhLHDiWnrzhzLGEg3j9cvwY240fNYdz+yXSH344UGNtu+F488EHPypwa0EHzWDyANHqgaCOFMWjYBSMglEwQgAATSdoDYQ+TtoAAAAASUVORK5CYII=","orcid":"","institution":"Alexandria University","correspondingAuthor":true,"prefix":"","firstName":"Nermeen","middleName":"El","lastName":"Sebaie","suffix":""},{"id":617056289,"identity":"687d001e-bbc8-486b-b0d9-16d44d7d891e","order_by":1,"name":"Hanan Morsi","email":"","orcid":"","institution":"College of Medicine, Academy of Science, Technology, and Maritime Transport","correspondingAuthor":false,"prefix":"","firstName":"Hanan","middleName":"","lastName":"Morsi","suffix":""},{"id":617056290,"identity":"daccfb3f-5da8-4001-b247-8f25aa52fb08","order_by":2,"name":"Ahmed Abdelzaher","email":"","orcid":"","institution":"Mubarak Al Kabeer Hospital","correspondingAuthor":false,"prefix":"","firstName":"Ahmed","middleName":"","lastName":"Abdelzaher","suffix":""},{"id":617056291,"identity":"b871b101-d6e4-44e2-9cc4-69ff071a0509","order_by":3,"name":"Ahmed El-Beheiry","email":"","orcid":"","institution":"Alexandria University","correspondingAuthor":false,"prefix":"","firstName":"Ahmed","middleName":"","lastName":"El-Beheiry","suffix":""}],"badges":[],"createdAt":"2026-03-28 14:08:15","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-9253327/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-9253327/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":106540627,"identity":"bf747912-2dc0-4953-b3c3-bb230b09832c","added_by":"auto","created_at":"2026-04-09 16:01:49","extension":"jpeg","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":58881,"visible":true,"origin":"","legend":"\u003cp\u003eFlow chart of the enrolling process of the study and reasons for patient exclusion.\u003c/p\u003e","description":"","filename":"floatimage1.jpeg","url":"https://assets-eu.researchsquare.com/files/rs-9253327/v1/ede4d9f17255ec8a5228ceef.jpeg"},{"id":106724854,"identity":"d4a461c2-a450-4ed3-a41a-30a8c8325175","added_by":"auto","created_at":"2026-04-12 18:30:08","extension":"jpeg","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":766974,"visible":true,"origin":"","legend":"\u003cp\u003eMR images of the different parts of the optic pathway with locations of measurements on axial T2-weighted turbo spin echo images (A) the intraorbital optic nerve, (B) the pre-chiasmatic optic nerve segment and (C) the optic tract. Central height of the optic chiasm was obtained on a reformatted coronal plane.\u003c/p\u003e","description":"","filename":"floatimage2.jpeg","url":"https://assets-eu.researchsquare.com/files/rs-9253327/v1/6c36758175229e78d4abf31f.jpeg"},{"id":106540628,"identity":"0ee5fd8a-a021-4557-a866-bdaaf2c9d2bb","added_by":"auto","created_at":"2026-04-09 16:01:49","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":210541,"visible":true,"origin":"","legend":"\u003cp\u003eA scatterplot showing various optic nerve measurements against age, all reveal a positive correlation between age and the diameter measured.\u003c/p\u003e","description":"","filename":"floatimage3.png","url":"https://assets-eu.researchsquare.com/files/rs-9253327/v1/596284728355db77ee6f1249.png"},{"id":106726567,"identity":"54b692bd-fded-45e1-9291-35d964e70094","added_by":"auto","created_at":"2026-04-12 18:36:34","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":1642639,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-9253327/v1/f1e0e035-36e6-4d40-a9b0-5f33e8475db5.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"Optic Pathway Measurements on MRI: Normal Values in the Pediatric Population","fulltext":[{"header":"Introduction","content":"\u003cp\u003eEarly diagnosis of optic pathway disorders in the pediatric population is important as many disease entities can be seen affecting the optic pathway, such as hypoplasia, atrophy, inflammation, demyelinating, and neoplasia [\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e]. These pathologies can result in an increase or decrease in the diameter of different optic pathway structures. Although subjective evaluation can detect diseases affecting the visual pathway, objective measurements are more valuable for timely diagnosis [\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eOptic nerve hypoplasia (ONH) is the most common congenital optic disc anomaly. It is a non-progressive condition that can be isolated or associated with abnormalities of the pituitary gland and brain [\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e]. Patients may present with poor vision, nystagmus, neurologic symptoms, or endocrine dysfunction [\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e, \u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e]. Measuring different segments of the optic pathway can be a critical tool for the diagnosis of ONH; however, accurate imaging assessment requires knowledge of the normal dimensions of these structures. While different diagnostic modalities can study the disc portion of the optic nerve, MR imaging is superior due to its ability to visualise the whole optic pathway with high soft-tissue resolution [\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eLimited literature is available regarding the normal size of the intraorbital and intracranial optic nerve as well as the optic chiasm and optic tract in children, and a sufficient number of normative data are still lacking. Our study aimed to establish a standardised method for measuring the optic pathway on MRI in the pediatric population, particularly in the early years and to report normal values of the optic pathway structures in pediatric patients up to 6 years of age using normal brain MRIs.\u003c/p\u003e"},{"header":"Patients and Methods","content":"\u003cp\u003eThis was a retrospective study carried out by the Department of Diagnostic and Interventional Radiology of our institution. The study was approved by the institutional review board, and informed consent was waived.\u003c/p\u003e \u003cdiv id=\"Sec3\" class=\"Section2\"\u003e \u003ch2\u003ePatient selection\u003c/h2\u003e \u003cp\u003eThe study took place over a period from January 2020 through May 2024. We retrospectively analysed the brain MR images of pediatric patients from infants to 6 years of age, who presented to our institution with symptoms or signs that are likely not related to involvement of the visual pathway, such as epilepsy, mild head trauma, ear pathologies or headache. Scans that were interpreted as normal by one of two neuroradiologists (NE, AA) with 8 and 15 years of experience, respectively, were included in the study. Exclusion criteria consisted of a history of prematurity (\u0026lt;\u0026thinsp;34 weeks), brain or ocular surgery, and MRI findings of cerebral ischemia, haemorrhage, atrophy or increased intracranial pressure. MRI studies that were degraded by motion or with poor visualisation of the optic nerve were also excluded. The exclusion flowchart is shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e\n\u003ch3\u003eMagnetic resonance imaging and measurements\u003c/h3\u003e\n\u003cp\u003eMRI scans were obtained on a 1.5T scanner (SOMATOM Definition Edge, Siemens, Germany) using a 16-channel head coil. Axial T2-weighted turbo spin echo images of the brain were used for optic nerve (intraorbital, pre-chiasmatic) and optic tract measurements. A Coronal T2-weighted turbo spin echo images, angled perpendicular to the long axis of the hippocampal body, were used for optic chiasm measurements. This sequence was routinely obtained in patients presenting with epilepsy. Acquisition parameters were as follows: repetition time (TR): 3,000\u0026ndash;6,000 ms, echo time (TE): 80\u0026ndash; 131 ms, section thickness 3 mm, intersection gap 0 mm, field of view 210 mm, and matrix 256\u0026times;256.\u003c/p\u003e\n\u003ch3\u003eMeasurements\u003c/h3\u003e\n\u003cp\u003eA total of seven measurements were performed for each patient, consisting of three bilateral measurements (intraorbital optic nerve, pre-chiasmatic optic nerve and optic tract), and one measurement in the midline (median height of the chiasm), as shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e. Bilateral measurements of the transverse diameter of the intraorbital optic nerve were performed perpendicular to the longitudinal axis of the optic nerve at 3 mm behind the globe without including the optic nerve sheath (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003eA). The width of the pre-chiasmatic optic nerve was obtained at its mid-segment, approximately 5 mm posterior to the optic canal (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003eB). Measurements of each optic tract diameter were performed at the level of the anterior border of the cerebral peduncle (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003eC). If the measurement could not be performed within 1\u0026ndash;2 mm of the intended location, or if the discrete margins of the nerve were not clearly visualized; the nerve was considered not measurable. The measurement of the optic chiasm was obtained on coronal sections at the slice where the maximum transverse diameter of the chiasm was visualized, and the central height of the chiasm was measured exactly at the midline perpendicular to the longitudinal axis of the chiasm (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003eD). The measurements were recorded into six groups, stratified by the patient\u0026rsquo;s age on the day of the MRI scan: Group I, 0 to 6 months; Group II, 6m to 1y; Group III, 1 to 2 years; Group IV, 2 to 3 years; Group V, 3 to 4 years and group VI, 4 to 6 years. All measurements were obtained using the built-in digital caliper tool in our Picture Archiving and Communication System (PACS). In some cases, measurements were performed on one side; if the other side was not delineated. Measurements were obtained by two neuroradiologists (NE, AA). The measurements of the two readers were used to calculate the inter-observer reproducibility. The average of the two measurements was used for the statistical analysis.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e\n\u003ch3\u003eStatistics\u003c/h3\u003e\n\u003cp\u003eData analysis was performed by SPSS software, version 25 (SPSS Inc., PASW statistics for windows version 25. Chicago: SPSS Inc.). Data normality was assessed using Kolmogrov-Smirnov test. Differences between the right and left sides and between males and females were evaluated using the Student \u003cem\u003et\u003c/em\u003e test. There was neither side nor sex differences, so bilateral variables were averaged across the two sides. The mean values and standard deviations (SD) of the intraorbital optic nerve, pre-chiasmatic optic nerve, optic chiasm and optic tract diameters were calculated and stratified by each age group. Statistical differences of the mean values among each age group were analysed by using One Way ANOVA test with Post Hoc Tukey test to detect pair-wise comparison. Finally, measurement results were plotted versus age, and Pearson correlation coefficient was calculated. Intraclass correlation coefficients (ICC) with 95% confidence intervals were used to evaluate the interobserver reproducibility of the measurements. Inter-observer agreement was defined as excellent (\u0026ge;\u0026thinsp;0.81), good (0.61\u0026ndash;0.80), moderate (0.41\u0026ndash;0.60), fair (0.21\u0026ndash;0.40), and poor (\u0026le;\u0026thinsp;20).\u003c/p\u003e"},{"header":"Results","content":"\u003cp\u003eA total of 104 MRI studies of the brain were included, there were 65 males and 39 females. The mean age of all the patients was 27\u0026thinsp;\u0026plusmn;\u0026thinsp;19 months (age range: 2\u0026ndash;66 months). Optic nerve (intraorbital and pre-chiasmatic), and optic tract measurements did not differ between the right and left sides or between males and females. Interobserver agreement was excellent, with an intraclass correlation coefficient of 0.845 (95% CI, 0.819\u0026ndash;0.836; P, .001), 0.881 (95% CI, 0.871\u0026ndash;0.888; P, .001), 0.860 (95% CI, 0.840\u0026ndash;0.873; P, .001) and 0.981 (95% CI, 0.971\u0026ndash;0.988; P, .001), for the introrbital optic nerve, pre-chiasmatic nerve, optic tract and optic chiasm respectively.\u003c/p\u003e \u003cp\u003eAxial imaging revealed a steady age-related increase in the mean diameter of the intraorbital optic nerve, from \u003cb\u003e1.90\u0026thinsp;\u0026plusmn;\u0026thinsp;0.11 mm\u003c/b\u003e in infants under 6 months to \u003cb\u003e2.64\u0026thinsp;\u0026plusmn;\u0026thinsp;0.14 mm\u003c/b\u003e in children aged 4\u0026ndash;6 years. Similarly, the pre-chiasmatic optic nerve diameter increased from \u003cb\u003e2.73\u0026thinsp;\u0026plusmn;\u0026thinsp;0.07 mm\u003c/b\u003e in the youngest group to \u003cb\u003e3.62\u0026thinsp;\u0026plusmn;\u0026thinsp;0.15 mm\u003c/b\u003e in the 4\u0026ndash;6-year cohort. The optic tract also exhibited progressive growth, with mean diameters rising from \u003cb\u003e1.82\u0026thinsp;\u0026plusmn;\u0026thinsp;0.09 mm\u003c/b\u003e (under 6 months) to \u003cb\u003e2.54\u0026thinsp;\u0026plusmn;\u0026thinsp;0.11 mm\u003c/b\u003e (4\u0026ndash;6 years). Optic chiasm measurements were available only in 46 pediatric patients with epilepsy. The central height of the optic chiasm measured \u003cb\u003e1.23\u0026thinsp;\u0026plusmn;\u0026thinsp;0.07 mm\u003c/b\u003e in infants\u0026thinsp;\u0026le;\u0026thinsp;6 months and increased to \u003cb\u003e1.74\u0026thinsp;\u0026plusmn;\u0026thinsp;0.05 mm\u003c/b\u003e in the 4\u0026ndash;6-year age group.\u003c/p\u003e \u003cp\u003eDifferences between age groups were evaluated for each measurement, a significant difference was observed for most of the measurements with an overlap observed between group III and IV for intraorbital optic and pre-chiasmatic and optic tract measurements, and between group II and III for pre-chiasmatic and optic tract measurements. There was a significant difference in optic chiasm measurements between group I and II. An overlap was observed between group III and IV as well as between group V and VI. The number of cases, mean diameter of the optic pathway structures stratified by age group, and details of comparison between groups are shown in Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e. The results were plotted in a measurement-versus-age comparison. The graphs show that there is a strong positive correlation between age and mean diameter of each of the intraorbital optic nerve (r\u0026thinsp;=\u0026thinsp;0.670, p \u0026lt; .001), pre-chiasmatic optic nerve (r\u0026thinsp;=\u0026thinsp;0.703, p \u0026lt; .001), optic tract (r\u0026thinsp;=\u0026thinsp;0.693, p \u0026lt; .001) as well as the height of the optic chiasm (r\u0026thinsp;=\u0026thinsp;0.716, p \u0026lt; .001) (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e).\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\u003eNumber of measured optic nerves, optic chiasm and optic tracts, mean diameters and standard deviation (SD) stratified by age groups\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"10\"\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 \u003cdiv align=\"left\" class=\"colspec\" colname=\"c9\" colnum=\"9\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c10\" colnum=\"10\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003eAge group\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eNumber\u003c/p\u003e \u003cp\u003eof cases\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colspan=\"2\" nameend=\"c4\" namest=\"c3\"\u003e \u003cp\u003eIntraorbital\u003c/p\u003e \u003cp\u003eoptic nerve\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colspan=\"2\" nameend=\"c6\" namest=\"c5\"\u003e \u003cp\u003ePre-chiasmatic\u003c/p\u003e \u003cp\u003eoptic nerve\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colspan=\"2\" nameend=\"c8\" namest=\"c7\"\u003e \u003cp\u003eOptic tract\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colspan=\"2\" nameend=\"c10\" namest=\"c9\"\u003e \u003cp\u003eOptic chiasm\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003en\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003emean\u0026thinsp;\u0026plusmn;\u0026thinsp;SD\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003en\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c6\"\u003e \u003cp\u003emean\u0026thinsp;\u0026plusmn;\u0026thinsp;SD\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c7\"\u003e \u003cp\u003en\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c8\"\u003e \u003cp\u003eMean\u0026thinsp;\u0026plusmn;\u0026thinsp;SD\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c9\"\u003e \u003cp\u003en\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c10\"\u003e \u003cp\u003emean\u0026thinsp;\u0026plusmn;\u0026thinsp;SD\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e0\u0026ndash;6\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e16\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e32\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e1.90\u0026thinsp;\u0026plusmn;\u0026thinsp;0.11\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e27\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e2.73\u0026thinsp;\u0026plusmn;\u0026thinsp;0.07\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e30\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e1.82\u0026thinsp;\u0026plusmn;\u0026thinsp;0.09\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e9\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c10\"\u003e \u003cp\u003e1.23\u0026thinsp;\u0026plusmn;\u0026thinsp;0.07\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e6 m- 1year\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e16\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e30\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e2.16\u0026thinsp;\u0026plusmn;\u0026thinsp;0.08\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e29\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e2.99\u0026thinsp;\u0026plusmn;\u0026thinsp;0.12 \u003csup\u003eA\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e28\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e1.99\u0026thinsp;\u0026plusmn;\u0026thinsp;0.10 \u003csup\u003eA\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e10\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c10\"\u003e \u003cp\u003e1.40\u0026thinsp;\u0026plusmn;\u0026thinsp;0.12\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e1\u0026ndash;2 year\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e17\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e34\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e2.27\u0026thinsp;\u0026plusmn;\u0026thinsp;0.095 \u003csup\u003eA\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e31\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e3.10\u0026thinsp;\u0026plusmn;\u0026thinsp;0.18 \u003csup\u003eAB\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e33\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e2.09\u0026thinsp;\u0026plusmn;\u0026thinsp;0.15 \u003csup\u003eA\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e8\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c10\"\u003e \u003cp\u003e1.60\u0026thinsp;\u0026plusmn;\u0026thinsp;0.09 \u003csup\u003eA\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e2\u0026ndash;3 year\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e20\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e40\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e2.33\u0026thinsp;\u0026plusmn;\u0026thinsp;0.18 \u003csup\u003eA\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e34\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e3.22\u0026thinsp;\u0026plusmn;\u0026thinsp;0.24 \u003csup\u003eB\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e39\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e2.24\u0026thinsp;\u0026plusmn;\u0026thinsp;0.17\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e7\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c10\"\u003e \u003cp\u003e1.58\u0026thinsp;\u0026plusmn;\u0026thinsp;0.11 \u003csup\u003eA\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e3\u0026ndash;4 year\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e15\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e30\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e2.48\u0026thinsp;\u0026plusmn;\u0026thinsp;0.15\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e24\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e3.42\u0026thinsp;\u0026plusmn;\u0026thinsp;0.18\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e30\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e2.36\u0026thinsp;\u0026plusmn;\u0026thinsp;0.10\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e8\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c10\"\u003e \u003cp\u003e1.70\u0026thinsp;\u0026plusmn;\u0026thinsp;0.05 \u003csup\u003eB\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e4\u0026ndash;6 year\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e20\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e40\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e2.64\u0026thinsp;\u0026plusmn;\u0026thinsp;0.14\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e36\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e3.62\u0026thinsp;\u0026plusmn;\u0026thinsp;0.15\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e40\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e2.54\u0026thinsp;\u0026plusmn;\u0026thinsp;0.11\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e14\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c10\"\u003e \u003cp\u003e1.74\u0026thinsp;\u0026plusmn;\u0026thinsp;0.05 \u003csup\u003eB\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cem\u003eP\u003c/em\u003e value*\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e104\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c4\" namest=\"c3\"\u003e \u003cp\u003e\u0026lt;\u0026thinsp;0.001\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c6\" namest=\"c5\"\u003e \u003cp\u003e\u0026lt;\u0026thinsp;0.001\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c8\" namest=\"c7\"\u003e \u003cp\u003e\u0026lt;\u0026thinsp;0.001\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c10\" namest=\"c9\"\u003e \u003cp\u003e\u0026lt;\u0026thinsp;0.001\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003ctfoot\u003e \u003ctr\u003e\u003ctd colspan=\"10\"\u003e\u003cb\u003e*\u003c/b\u003e\u003cem\u003eP\u003c/em\u003e value using One Way ANOVA test to assess the significance of the between-group comparisons, \u003csup\u003eA and b\u003c/sup\u003e Similar letters in same row denote non-significant difference between these age groups by post hoc Tukey test\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\u003eIn this study, we analysed the diameters of the optic pathway, including the width of the intraorbital, pre-chiasmatic optic nerve and the optic tract, as well as the height of the optic chiasm in pediatric patients from 0 to 6 years old on T2-weighted MR images of the brain. Our results showed that all structures increased with age, with significant differences between age groups in all measurements, independent of sex or eye laterality.\u003c/p\u003e \u003cp\u003eIn our study, the mean diameter of the intraorbital optic nerve in children up to 6 months of age measured at 3 mm behind the globe was 1.90\u0026thinsp;\u0026plusmn;\u0026thinsp;0.11 mm. Our measurements were slightly greater than those reported by Al-Haddad et al. [\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e] who found that the intraorbital optic nerve diameter in the same age group was 1.53\u0026thinsp;\u0026plusmn;\u0026thinsp;0.82 mm. The authors of this study used axial STIR images of the orbit at a 2\u0026ndash;3 mm section thickness, which could explain this difference. Janthami et al. [\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e] focused on measuring the intraorbital optic nerve in the first 4 years of age and stratified them into 4 age groups. They used routine brain sections as in our study; however, our measurements for the intraorbital optic nerve were smaller than the measurements in this study for all age groups (Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e). This could be explained by the greater section thickness they used (4\u0026ndash;6 mm), in comparison with our study as routine axial T2-weighted images of the brain for pediatric patients in our institution were obtained with 3 mm thickness. At the age group from 2 years up to 6 years in our study, the mean diameter of the intraorbital optic nerve increased from 2.17\u0026thinsp;\u0026plusmn;\u0026thinsp;0.21 mm in children up to 3 years, to 2.57\u0026thinsp;\u0026plusmn;\u0026thinsp;0.17 mm in the age group from 4\u0026ndash;6 years. Markat et al. [\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e] reported that the mean axial diameter of the retrobulbar optic nerve was 2.99\u0026thinsp;\u0026plusmn;\u0026thinsp;0.29 mm at the age group ranging from 4\u0026ndash;6 years.\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\u003eDiameters of the intraorbital optic nerve measured axially 3 mm behind the globe in different studies\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"9\"\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 \u003cdiv align=\"left\" class=\"colspec\" colname=\"c9\" colnum=\"9\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colspan=\"9\" nameend=\"c9\" namest=\"c1\"\u003e \u003cp\u003eIntraorbital optic nerve measured axially 3 mm behind the globe (retrobulbar)\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eAge group\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eAlhaddad et al. \u003csup\u003e1\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eOur study\u003csup\u003e2\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eAge group\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003eMarkat et al.\u003csup\u003e3\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003eOur study\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003eAge group\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003eJanthami et al.\u003csup\u003e4\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003eOur study\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u0026lt;\u0026thinsp;6 months\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e1.53\u0026thinsp;\u0026plusmn;\u0026thinsp;0.82\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e1.90\u0026thinsp;\u0026plusmn;\u0026thinsp;0.11\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0\u0026ndash;3 years\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e2.86\u0026thinsp;\u0026plusmn;\u0026thinsp;0.31\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e2.17\u0026thinsp;\u0026plusmn;\u0026thinsp;0.21\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e0\u0026ndash;1 year\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e2.3\u0026thinsp;\u0026plusmn;\u0026thinsp;0.4\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e2.02 \u0026plusmn; 0.17\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e6m to 2 years\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e2.03\u0026thinsp;\u0026plusmn;\u0026thinsp;0.30\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e2.22\u0026thinsp;\u0026plusmn;\u0026thinsp;0.10\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e4\u0026ndash;6 years\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e2.99\u0026thinsp;\u0026plusmn;\u0026thinsp;0.29\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e2.57\u0026thinsp;\u0026plusmn;\u0026thinsp;0.17\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e1\u0026ndash;2 years\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e2.6\u0026thinsp;\u0026plusmn;\u0026thinsp;0.2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e2.27\u0026thinsp;\u0026plusmn;\u0026thinsp;0.09\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e2\u0026ndash;6 years\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e2.20\u0026thinsp;\u0026plusmn;\u0026thinsp;0.30\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e2.48\u0026thinsp;\u0026plusmn;\u0026thinsp;0.21\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e2\u0026ndash;3 years\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e2.4\u0026thinsp;\u0026plusmn;\u0026thinsp;0.3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e2.33\u0026thinsp;\u0026plusmn;\u0026thinsp;0.18\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e3\u0026ndash;4 years\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e2.9\u0026thinsp;\u0026plusmn;\u0026thinsp;0.4\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e2.48\u0026thinsp;\u0026plusmn;\u0026thinsp;0.15\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003ctfoot\u003e \u003ctr\u003e\u003ctd colspan=\"9\"\u003e\u003csup\u003e1\u003c/sup\u003e Using axial short time inversion recovery (STIR) sequence of the orbit with 2 to 3 mm section thickness; \u003csup\u003e2\u003c/sup\u003e Axial T2-weighted turbo spin echo images of the brain 3 mm section thickness; \u003csup\u003e3\u003c/sup\u003e using high-resolution 3dimensional T2-weighted fast spin echoo MR sequence 0.5 to 0.6 mm section thickness; \u003csup\u003e4\u003c/sup\u003e using axial T2-weighted turbo spin echo image of the brain 4 to 6 mm section thickness.\u003c/td\u003e\u003c/tr\u003e \u003c/tfoot\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003eDemonstrated from the previous comparison, there are some differences between measurements of the intraorbital optic nerve in the same age group with different acquisition sequences and different slice thickness. The optic pathway in children consists of small structures, which can make accurate and reproducible measurements challenging. Similar to previous studies [\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e, \u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e], we used an axial T2-weighted turbo spin echo sequence of the brain for different optic pathway measurements. We believe that this is a more practical way to assess the optic pathway, and it is the technique that most neuroradiologists would adopt to make their diagnosis. Methods adopted in other studies [\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e, \u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e] typically involved dedicated orbital MRI fat-saturated acquisition sequences along the axis of the optic nerve in addition to the commonly acquired sequences and extended the scan time for each patient. It can also involve imaging post-processing procedures, rendering it difficult to implement in routine clinical work. Furthermore, an additional thin slice thickness sequence on the MRI in pediatric patients means adding more time on the scanner and more time in sedation [\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e]. In the setting of suspected optic nerve hypoplasia, assessment of optic nerve size is mostly done as part of the evaluation of other structural brain abnormalities.\u003c/p\u003e \u003cp\u003eMarkat et al. [\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e] found a strong inter-reader agreement for the measurement of the intracranial segment of the optic nerve. They recorded that the width of the pre-chiasmatic optic nerve at its mid portion was 3.75\u0026thinsp;\u0026plusmn;\u0026thinsp;0.28 mm at the age group of 4\u0026ndash;6 years, which is similar to our results at the same age group (3.62\u0026thinsp;\u0026plusmn;\u0026thinsp;0.15 mm). For optic tract measurements, the mean diameter among patients younger than 6 months was 1.82\u0026thinsp;\u0026plusmn;\u0026thinsp;0.09 mm. Oyama et al. found that the mean of the width of the optic tract was 1.5\u0026thinsp;\u0026plusmn;\u0026thinsp;0.1 mm in neonates with no intracranial abnormalities at term-equivalent age. AS each component of the optic pathway grows at proportional rates, measurement of the optic pathway can be obtained at any point, and a suspicion for the presence of ONH can still be raised [\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eONH is the most common congenital optic disc anomaly. The diagnosis of ONH is done by ophthalmoscopic confirmation of a small optic disc, often in combination with fundus photography [\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e]. Fundus photography overcomes problems with optic disc visualisation and can provide a measurement of the optic disc size that cannot be obtained by ophthalmoscopic examination. However, fundus photography in children is difficult in the presence of nystagmus or high refractive errors, which occur frequently in patients with ONH [\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eKruglyakova J et al. [\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e] performed MRI in addition to fundus photography in children with suspected ONH before 2 years of age. Using fundus photographs, the ratio of the horizontal disc diameter (DD) to the distance between the macular and the temporal edge of the disc (DM) was measured, and the DD/DM ratio of optic nerves with normal vision was estimated to be greater than 0.35. They reported that all eyes with a DD/DM ratio of optic nerves less than 0.35 had an optic nerve diameter\u0026thinsp;\u0026lt;\u0026thinsp;1.7 mm on MRI and diagnosed as having ONH, suggesting that optic nerve diameter\u0026thinsp;\u0026lt;\u0026thinsp;1.7 mm is 100% sensitive for the diagnosis of ONH [\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e]. The minimum width of the intra-orbital optic nerve measured in our study was 1.8 mm.\u003c/p\u003e \u003cp\u003eNeuroimaging in patients with the diagnosis of ONH is essential due to the high association with brain and pituitary abnormalities. The most prevalent neuroimaging findings included abnormalities of the corpus callosum, septum pellucidum and pituitary gland, including absent or ectopic posterior pituitary bright spot and infundibular hypoplasia [\u003cspan additionalcitationids=\"CR15\" citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e]. All patients with a pituitary gland malformation on imaging develop hypothalamic-pituitary dysfunction. It is noteworthy that 66% of patients with a normal pituitary gland on MRI can also develop hypothalamic-pituitary dysfunction [\u003cspan additionalcitationids=\"CR17 CR18 CR19\" citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e]. The presence of ONH alone is a risk factor for the development of hypothalamic-pituitary dysfunction, independent of the presence of various anatomic abnormalities of the brain. Other reported neuroimaging abnormalities included schizencephaly, arachnoid cysts, pachygyria, polymicrogyria, cortical heterotopia, white matter hypoplasia, and hydrocephalus [\u003cspan additionalcitationids=\"CR21\" citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eJeunger et al. [\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e] assessed optic chiasm height using a standard 3D T1-weighted MRI sequence and reported that measuring optic chiasm dimensions is easier and more reproducible than intraorbital optic nerve measurements. The optic chiasm is a rather fixed structure and less vulnerable to motion artefacts compared to orbital optic nerve measurement, less variable in morphology, bigger in dimensions and, thus, a simple target for MR investigations. However, the coronal plane should be perpendicular to the optic chiasm; otherwise, measurements at varying angles to the course of the optic chiasm will result in higher values and variance [\u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eA few limitations must be brought to attention regarding this study. We didn\u0026rsquo;t use coronal sections for measuring the intraorbital optic nerve because routine brain MR images were not obtained perpendicular to the axis of each optic nerve. Since none of the patients exhibited overt visual symptoms or signs, direct comparison with a reference standard (e.g., ophthalmoscopic findings) was not possible.\u003c/p\u003e"},{"header":"Conclusions","content":"\u003cp\u003eIt is important to define standardized locations along the course of the optic pathway for accurate assessment. We measured the width of the intraorbital optic nerve 3 mm behind the globe, the pre-chiasmatic optic nerve at its mid segment, and the optic tract at the anterior border of the brain stem on axial T2-weighted images. On coronal T2-weighted images acquired perpendicular to the optic chiasm; we measured the central height of the chiasm. We reported normal measurements of the optic pathway structures, providing reference values in children from birth to 6 years of age using routine brain MRI.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003e\u003cu\u003eAcknowledgements\u003c/u\u003e\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eNot applicable\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e\u003cu\u003eEthics approval and consent to participate\u003c/u\u003e\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eApproval for this study was obtained from the Research Ethics Committee of Faculty of Medicine, Alexandria University (IRB NO: 00012098; FWA NO: 00018699; Serial NO: 0306769). All study procedures were carried out in accordance with the Declaration of Helsinki regarding research involving human subjects. Consent to participate was waived (retrospective study).\u003cu\u003e\u0026nbsp;\u003c/u\u003e\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e\u003cu\u003eConsent for publication\u003c/u\u003e\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eNot applicable.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e\u003cu\u003eAvailability of data and material\u003c/u\u003e\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe datasets used and analyzed during the current study are available from the corresponding author on reasonable request.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e\u003cu\u003eCompeting interests\u003c/u\u003e\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe authors declare that they have no competing interests.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e\u003cu\u003eFunding\u003c/u\u003e\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eNone (authors personal contribution).\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\u003cli\u003e\u003cspan\u003eKanda T, Miyazaki A, Zeng F, et al (2020) Magnetic resonance imaging of intraocular optic nerve disorders: Review article. Pol J Radiol 85:67\u0026ndash;81\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eSwienton DJ, Thomas AG (2020) The visual pathway-functional anatomy and pathology. Semin Ultrasound CT MR 2014 35:487\u0026ndash;503\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eQian X, Fouzdar Jain S, Morgan LA, Kruse T, Cabrera M, Suh DW (2018) Neuroimaging and endocrine disorders in paediatric optic nerve hypoplasia. Br J Ophthalmol 102:906\u0026ndash;910\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eNetzel AN, High R, Suh DW (2019) Optic nerve hypoplasia: A retrospective analysis of clinical presentation and disease severity. Clin Ophthalmol 13:2607\u0026ndash;2616\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eGarcia-Filion P, Borchert M (2013) Optic nerve hypoplasia syndrome: a review of the epidemiology and clinical associations. Curr Treat Options Neurol 15:78\u0026ndash;89\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eLenhart PD, Desai NK, Bruce BB, Hutchinson AK, Lambert SR (2014) The role of magnetic resonance imaging in diagnosing optic nerve hypoplasia. Am J Ophthalmol 158(6):1164\u0026ndash;1171.e2\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eAl-Haddad CE, Sebaaly MG, Tutunji RN, et al (2018) Optic Nerve Measurement on MRI in the Pediatric Population: Normative Values and Correlations. AJNR Am J Neuroradiol 39:369\u0026ndash;374\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eJanthanimi P, Dumrongpisutikul N (2019) Pediatric optic nerve and optic nerve sheath diameter on magnetic resonance imaging. Pediatr Radiol 49:1071\u0026ndash;1077\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eMarkart S, Wildermuth S, Geiss J, et al (2022) Pediatric reference values of anterior visual pathway structures measured with axis-correction on high-resolution 3D T2 fast spin echo sequences. BMC Pediatr; 22(1):584\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eOyama J, Mori K, Imamura M, Mizushima Y, Tateishi U (2016) Size of the intracranial optic nerve and optic tract in neonates at term-equivalent age at magnetic resonance imaging. Pediatr Radiol 46:527\u0026ndash;33\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eJuenger V, Cooper G, Chien C, et al (2020) Optic chiasm measurements may be useful markers of anterior optic pathway degeneration in neuromyelitis optica spectrum disorders. Eur Radiol 30 (9):5048\u0026ndash;5058\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eKruglyakova J, Garcia-Filion P, Nelson M, Borchert M (2020) Orbital MRI versus fundus photography in the diagnosis of optic nerve hypoplasia and prediction of vision. Br J Ophthalmol 104:1458\u0026ndash;1461\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eSkriapa-Manta A, Venkataraman AP, Olsson M, Nilsson M, Te\u0026auml;r Fahnehjelm (2024) Characteristic deviations of the optic disc and macula in optic nerve hypoplasia based on OCT. Acta Ophthalmol May 23\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eTaylor D (2007) Developmental abnormalities of the optic nerve and chiasm. 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Eur J Radiol 172:111332.\u003c/span\u003e\u003c/li\u003e\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":true,"highlight":"","institution":"","isAcceptedByJournal":false,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true},"keywords":"optic nerve, optic chiasm, optic tract, optic pathway, normal measurments","lastPublishedDoi":"10.21203/rs.3.rs-9253327/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-9253327/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003ch2\u003eBackground\u003c/h2\u003e \u003cp\u003eDifferent pathologies can affect the optic pathway structures in children, and early detection of these pathologies requires knowledge of their normal measurements. Our study aimed to establish a standardised method for measuring the optic pathway structures and report their normal values in children up to six years of age using brain MRI.\u003c/p\u003e\u003ch2\u003eMethods\u003c/h2\u003e \u003cp\u003eWe retrospectively analysed the brain MR images of pediatric patients from infants to six years of age; scans that were interpreted as normal were included in the study. Axial T2-weighted images were used for optic nerve (intraorbital, pre-chiasmatic) and optic tract measurements. Coronal T2-weighted images were used for optic chiasm measurements. Patients were stratified into six age groups for analysis.\u003c/p\u003e\u003ch2\u003eResults\u003c/h2\u003e \u003cp\u003eA total of 104 MRI studies of the brain were included; there were 65 males and 39 females. The mean age of all the patients was 26\u0026thinsp;\u0026plusmn;\u0026thinsp;12 months. An increase in diameter was observed with age for all measurements. There is a strong positive correlation between age and mean diameter of each of the intraorbital optic nerve (r\u0026thinsp;=\u0026thinsp;0.670), pre-chiasmatic optic nerve (r\u0026thinsp;=\u0026thinsp;0.703), optic tract (r\u0026thinsp;=\u0026thinsp;0.693), as well as the height of the optic chiasm (r\u0026thinsp;=\u0026thinsp;0.716).\u003c/p\u003e\u003ch2\u003eConclusions\u003c/h2\u003e \u003cp\u003eUsing axial and coronal brain MRI, we suggested standardised locations for measuring the optic pathway structures and reported their normal values in children from birth to 6 years of age.\u003c/p\u003e","manuscriptTitle":"Optic Pathway Measurements on MRI: Normal Values in the Pediatric Population","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2026-04-09 16:01:45","doi":"10.21203/rs.3.rs-9253327/v1","editorialEvents":[{"type":"communityComments","content":0}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"61a78d9a-7b38-4213-b9f1-0f1e57b3f3f8","owner":[],"postedDate":"April 9th, 2026","published":true,"recentEditorialEvents":[{"type":"editorInvitedReview","content":"","date":"2026-05-08T06:53:44+00:00","index":17,"fulltext":""},{"type":"reviewerAgreed","content":"148019212674554226873927758371375140251","date":"2026-05-01T04:25:11+00:00","index":16,"fulltext":""}],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[],"tags":[],"updatedAt":"2026-04-09T16:01:45+00:00","versionOfRecord":[],"versionCreatedAt":"2026-04-09 16:01:45","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-9253327","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-9253327","identity":"rs-9253327","version":["v1"]},"buildId":"XKTyCvWXoU3ODBz1xrDgd","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}