Foveal Hypoplasia Grading in 95 Cases of Congenital Aniridia: Correlation to Phenotype and PAX6 Genotype

Abstract

Purpose: To correlate the degree of foveal hypoplasia in congenital aniridia with visual acuity, iris phenotype, and PAX6 mutations.

Design: Retrospective case series.

Methods: Ninety-five consecutive patients with high-quality spectral-domain optical coherence tomography records and available genotype were included in a single referral center. Iris hypoplasia was classified as complete, presence of iris root or remnants, and mild atypical aniridia. Spectral-domain optical coherence tomography images were assessed to classify foveal hypoplasia as grade 1 to 4 and to determine mean thicknesses for retinal layers. For statistical analysis 1 eye for each patient was used and 1 member of the same family has been included (n = 76 eyes).

Results: Most eyes (n= 158/169, 93.5%) showed variable degree of foveal hypoplasia. PAX6-positive patients presented higher degree of foveal hypoplasia than patients negative for PAX6 (P < .0001). PAX6 deletions, PAX6 variants subjected to nonsense-mediated decay and C-terminal extension variants were mostly associated with grade 3 or 4 foveal hypoplasia. Deletions restricted to the 3' flanking regulatory regions of PAX6 were associated with grade 1 or 2 foveal hypoplasia (P < .0001). Best-corrected visual acuity was higher and foveal outer retinal layers were thicker in patients with deletions in the 3' regulatory region of PAX6 (P = .001 and P < .0001). Patients with missense mutations presented with variable degree of foveal hypoplasia. The degree of foveal hypoplasia was most frequently correlated with the severity of iris defects, with 95% of eyes with complete aniridia presenting grade 3 or 4 foveal hypoplasia (P = .005). However, among eyes with mild iris phenotype, 70% (n=9/13) showed severe foveal hypoplasia.

Conclusions: All types of PAX6 variants, even those associated with mild iris defects, may be at risk for severe foveal hypoplasia with poor visual prognosis, except for deletions restricted to the 3' regulatory PAX6 regions.