Strabismus, roving eye movements (and nystagmus), and visual inattention are found in nearly all patients. Esotropia with defective abduction seems to be the most common oculomotor finding and may be present at birth. Cataracts, ocular colobomas, oculomotor apraxia, disc pallor, and glaucoma have also been reported. Vision is always subnormal. Reports of ocular disease before modern genotyping are not specific to the subtypes of CDG I now recognized.
This is a congenital, progressive disorder of photoreceptor degeneration with a later onset of progressive pigmentary retinopathy. It is described in some cases as a typical retinitis pigmentosa. The ERG is abnormal in all patients even if the pigmentary pattern is atypical for RP. Rod responses are usually absent while the cone b-wave implicit time is delayed. The degree of photoreceptor damage is variable, however. Extended retinal function among younger patients suggest that the ‘on-pathway’ evolving synapses in the outer plexiform layer among photoreceptors, bipolar cells, and horizontal cells is severely dysfunctional.