Clinical and imaging characteristics of myelinated retinal nerve fibers: associations with refractive error and visual acuity

Abstract Purpose To characterize the clinical and imaging characteristics of myelinated nerve fibers (MNF) and evaluate their association with refractive error and visual acuity. Methods Retrospective observational case series of 367 eyes of 323 patients diagnosed with MNF between January 2013 and December 2025. Medical records were reviewed to assess the location and extent of MNF, along with optic disc and macular involvement. Best corrected visual acuity (BCVA) and refractive error were analyzed. 65 eyes of 63 patients with fundus photograph documentation were further analyzed for associations between clinical characteristics, refractive error, and visual acuity using univariate and multivariate regression analyses. The MNF extent was manually delineated by the trained graders using a freehand tool, excluding the optic disc, and measured in pixels. The optic disc area was similarly measured, and MNF extent was expressed in disc-area equivalents (the ratio of total area of MNF area to optic disc area). Amblyopia prevalence and its predictors were evaluated as a secondary outcome. Results The mean age at presentation was 37.23 years (range: 4 months to 91 years). Mean best-corrected visual acuity (BCVA) among 354 eyes (remaining were infants) was 0.59 ± 0.91 logMAR (range: 0-2.4). Spherical equivalent ranged from + 7.5 Diopters (D) to -20.5 D (mean:-3.33D ± -5.2D). Amblyopia was present in 24.5% (90/367) of eyes and optic disc was involved in 96.9% of eyes with photographic analysis. On univariate analysis, temporal location of MNF (p value = 0.010), greater MNF extent (p value = < 0.0001), and macular involvement (p value = 0.002) were significantly associated with worse visual acuity. On multivariate analysis MNF extent (β = 0.014, 95% CI: 0.005 to 0.021, p = 0.003) remained significantly associated with poorer visual acuity. Among 28 paediatric patients (< 18years), 14 patients had Straastma syndrome (the triad of MNF, myopia, and amblyopia) and underwent occlusion therapy. This subgroup demonstrated a mean spherical equivalent of -9.71 ± 3.52 D, axial length of 26.23 ± 1.77 mm. Conclusion Greater MNF extent and macular involvement are independently associated with worse visual acuity. Children with MNF should undergo careful cycloplegic refraction and assessment for amblyopia.