The relationship between foveal anatomy and retinal function in oculocutaneous albinism

To examine the relationship between multifocal ERG (mfERG) topography and peak cone density measured with adaptive optics scanning light ophthalmoscopy (AOSLO) in persons with albinism (PWA).

We obtained best corrected visual acuity (BCVA), mfERG, retinal imaging with AOSLO, and optical coherence tomography (OCT) data in seven PWA and one control. The relationship between central peak cone density, mfERG amplitude topography, and foveal hypoplasia (FH) grade was calculated using Spearman rank correlation. Parafoveal cone densities among a subset of PWA were compared to a previously reported control group.

All PWA had variably below average peak cone density, decreased BCVA, flattened mfERG topography, and FH. Higher peak cone density significantly correlated with higher peripheral mfERG amplitudes (r² = 0.73, p = 0.0049), but not central (r² = 0.25), and did not correlate with steeper (more normal) mfERG topography (r² = 0.031). Parafoveal cone densities did not greatly differ outside of the central 2° (within Ring 1) between PWA and those of previously reported controls.

The association of increased foveal cone packing with elevated peripheral, but not central mfERG amplitudes, suggests aberrant post-receptoral circuitry in the macula. The presence of excess connections between cone photoreceptors and bipolar cells, similar to the unrefined circuitry seen in fetal retinae, may underly the electrical dysfunction seen in these PWA, and explain why, even with milder FH and denser cone packing, normal visual acuity is often not achieved.