The eyes in albinism: clinical characteristics and their contribution to visual function

Abstract

Pigmentation and ocular deficits vary greatly in people with albinism. The aim of this thesis was to describe the whole phenotypic spectrum of albinism, identify the contributing factors to reduced visual acuity (VA), and investigate the relation between melanin and VA limiting factors. We proposed diagnostic criteria for patients with and without a genetic confirmation. A diagnosis of albinism can be made when patients have 3 major, or 2 major AND 2 minor criteria, or, in molecularly confirmed patients, 1 major or 2 minor criteria. Major criteria are: foveal hypoplasia grade ≥ 2, misrouting, and ocular hypopigmentation. Minor criteria are: nystagmus, hypopigmentation of skin/hair, fundus hypopigmentation grade 1, and foveal hypoplasia grade 1. We defined the optimal Visual Evoked Potential protocols for different ages, and chiasm-coefficient cut-off values for the presence of misrouting. Only nystagmus and foveal hypoplasia predicted visual acuity. We discovered that pendular nystagmus was associated with poorer VA and severe foveal hypoplasia, while jerk nystagmus was associated with better VA and less severe foveal hypoplasia.

We illustrated that despite normal pigmentation levels, patients can still have a severe ocular phenotype, and that the visual system can still develop normally in the presence of a severe melanin deficiency.