Visual function in Rett syndrome.

The authors examined refractive error, pattern onset visual evoked potentials, ocular posture and they performed internal and external eye examinations in 11 subjects with Rett syndrome (aged between four and 24 years) and 18 normal controls (aged between six and 20 years). Substantial refractive errors were common in the Rett syndrome group. Spectacle correction had never previously been worn and glasses were provided where appropriate. No subjects had nystagmus or optic nerve pallor and only one was strabismic. All subjects had recognisable and reproducible pattern-onset VEPs and latencies and amplitudes did not differ significantly from those of the controls. All demonstrated VEP thresholds of at least 24'. In contrast to other populations with profound disabilities, people with Rett syndrome have good function of the afferent visual pathways and, in view of their substantial refractive errors, are likely to benefit from spectacle correction.