Variability in Foveal Morphology in Albinism Assessed with SD-OCT

Abstract

Purpose: : Albinism is typically characterized by foveal hypoplasia, although recent data have demonstrated variation in the degree of hypoplasia. We sought to quantify foveal morphology in individuals with albinism and compare this to normal foveal morphology using newly developed foveal pit metrics.

Methods: : We recruited 139 individuals with normal vision (71 male, 68 female; mean age = 27 yrs) and 23 individuals with albinism (6 OA1, 17 OCA; mean age = 24 yrs). Cross-sectional and/or volumetric SD-OCT images of the macula were obtained using the Cirrus HD-OCT or the Bioptigen SD-OCT. Seven subjects were imaged using the hand-held probe of the Bioptigen system, as they were imaged off-site at the National Conference of the National Organization for Albinism and Hypopigmentation (NOAH). Custom Matlab software was used to derive estimates of the depth, diameter, slope, and volume of the foveal pit from the retinal thickness data sets. Dimensions of all OCT scans were corrected for individual differences in axial length in order to ensure accurate absolute measures of pit dimensions.

Results: : Normal foveal pit depth ranged from 0.032 to 0.177 mm, diameter ranged from 1.17 to 2.65 mm, and volume ranged from 0.024 to 0.21 mm³. We observed considerable variation in foveal morphology in individuals with albinism - 9 had planar retinal thickness, 6 had mounding at the incipient foveal location but no pit, 7 had mounding and a subtle foveal depression, and 1 had nearly normal foveal morphology (foveal depth = 0.028 mm, foveal diameter = 1.58 mm, foveal volume = 0.016 mm³).

Conclusions: : The spectrum of foveal morphology seen in albinism is greater than previously thought. The ability to accurately characterize foveal morphology represents an important first step in separating out retinal versus cortical contributions to visual deficits in these patients.

Keywords: imaging/image analysis: clinical • imaging methods (CT, FA, ICG, MRI, OCT, RTA, SLO, ultrasound) • retinal development