SYMPTOMS Nyctalopia, Vision loss, Visual field defects, Color vision defects
SIGNS Bilateral
RPE pigment clumping with subsequent chorioretinal atrophy that starts in the mid-periphery and spreads into the far periphery and posterior pole (the macula is affected last), Exposure of sclera, Exposure of large choroidal vessels, Posterior subcapsular cataracts (associated in 31% of patients)
Typically, the retinal vessels and optic nerve remain normal
WORK-UP Pupils, Color vision (abnormal), Full eye exam with dilation, Visual field, OCT of the macula, OCT-Angiography (presence of choriocapillaris loss), Fundus Autofluorescence, Fluorescein Angiography (presence of choriocapillaris loss), Indocyanine Green Angiography (presence of choriocapillaris loss), Fundus photos, Infrared photos, Electrodiagnostic testing (ERG: Abnormal / EOG), Dark adaptation (abnormal), Watzke-Allen test, Macular photostress test, Amsler grid
TREATMENT Give take home Amsler grid in order to monitor for macula involvement
Monitor. No treatment is effective
Recommend genetic counseling for other family members
If the patient develops poor vision, refer to low vision
If the patient presents with a visual significant posterior subcapsular cataract, refer for cataract surgery
FOLLOW-UP Patient should be seen back every 6-12 months
ETIOLOGY X-linked recessive progressive hereditary retinal dystrophy that occurs due to a mutation in the CHM gene which plays a key role in producing REP-1. This leads to damage of the photoreceptors, RPE, and choriocapillaris
DIFFERENTIAL DX Retinitis pigmentosa, Gyrate atrophy, “Salt and pepper" fundus, Ocular albinism
NOTES Symptoms are typically first noted during adolescence. Central vision loss typically occurs during the fourth or fifth decade of life
Female carriers may show mild RPE changes in the mid-peripheral retina that is not progressive