night-blindness

Patients note reduced vision in brightly-lit environments with onset in early adulthood and progressive central vision loss thereafter.   Nystagmus, photophobia, and dyschromatopsia may be present.  Younger individuals may complain of night blindness.  Visual fields show diffuse progressive suppression with relative sparing of selected areas such as the peripapillary region.  The ERG documents primary cone dystrophy but less involvement of the rods.  EOG testing in 4 patients showed reduced light-dark ratios.  Macular degeneration, attenuated vessels, subtle salt-and-pepper pigmentation, and spicular pigmentary deposits in the mid-periphery may be seen.

Retinitis pigmentosa consists of a group disorders with great clinical and genetic heterogeneity.  The ocular disease is characterized by night blindness, field constriction, and pigmentary changes in the retina.  The later is sometimes described as having a 'bone corpuscle' appearance with a perivascular distribution.  A ring scotoma is sometimes evident.  Age of onset and rate of progression is highly variable, even within families.

The X-linked form described here is a pigmentary retinopathy but sometimes labeled chorioretinal degeneration because of the extensive involvement of the choroid.  The clinical picture is sometimes referred to by the out-dated term 'choroidal sclerosis'.  It is often apparent in males during early childhood and they usually have early deterioration in central vision.  Some carrier females experience vision loss and have mild fundus abnormalities but these do no usually appear until middle age and are usually slowly progressive.  The ERG shows abnormalities in both sexes but these are highly variable.  Older males may have a waxy pallor of the optic nerve.  Posterior subcapsular cataracts are common.  The vitreous may contain fine, colorless particles even before fundus changes are evident.  Prognosis is highly variable but many patients eventually become legally blind by the age of 30 years.