Investigating Determinants of Visual Outcome in Foveal Hypoplasia

Authors

• KD Bordonada
• LA Huryn
• WM Zein
• BP Brooks
• RB Hufnagel

Abstract

The fovea is an avascular zone of the retina rich in cone photoreceptors that plays an essential role in human vision, as it is responsible for improved visual acuity (VA) and color vision. Foveal hypoplasia (FH) is the incomplete formation of foveal architecture, including a lack of foveal depression and outer nuclear layer thickening with continuity of inner retinal layers. This disease is commonly seen with albinism or albinism-spectrum syndromes, aniridia, and as an isolated phenomenon. We analyzed data from a cohort of 209 NEI patients with FH, to describe relationships between retinal structure and visual function. Information on foveal imaging, VA, genetic testing, refractive error, and nystagmus was collected. Optical coherence tomography images were graded based on a published scale and analyzed by individual features: foveal contour; extrusion of inner retinal layers (IRL); widening of the outer nuclear layer (ONL); and lengthening of the outer segments (OS). We optimized and compared several grading schemas for FH using qualitative and quantitative measures, to find features of the fovea that are better predictors of VA. Our data show that nystagmus and foveal anatomy are independent determinants of VA, and that refractive error has higher variability with nystagmus and severe FH. Each component of FH has a different influence on the patient’s visual outcome, with IRL extrusion and ONL widening having a greater influence on VA than OS lengthening and foveal pit. We find that normalized IRL and ONL thickness provides a focused grading system that could be implemented in clinical trials and research settings.

Scientific Focus Area: Genetics and Genomics

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