ERG anomalies

Retinal Cone Dystrophy 3B

Clinical Characteristics
Ocular Features: 

This is a degenerative disorder in which patients have a progressive deterioration of visual acuity and color vision.  Most patients have significant myopia.  Visual difficulties begin in early childhood with acuity of 20/100 or worse by the second decade of life.  Color vision deficits can be detected in the second decade but nyctalopia occurs later in young adults.  Photophobia is a prominent symptom.  The ERG shows reduced and delayed cone responses.  Rod responses to low intensity flashes are undetectable but increased stimulus intensity leads to an abrupt increase in amplitude, often exceeding the upper limits of normal.

The fundus appears normal in some patients but foveal or parafoveal atrophy, a macular bull’s eye, hyperfluorescence anomalies, and a generalized fine pigmentary retinopathy have been reported.  There may be some temporal pallor in the optic nerves.  Nystagmus and strabismus may be present.

Systemic Features: 

No systemic disease has been reported.

Genetics

This is an autosomal recessive disorder resulting from homozygous or compound heterozygous mutations in the KCNV2 gene (9p24.2).

Pedigree: 
Autosomal recessive
Treatment
Treatment Options: 

No effective treatment is available for this dystrophy.  Low vision aids and tinted lenses may be helpful.

References
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