The congenital stationary night blindness (CSNB) is a non-progressive group of retinal disorders that is clinically and genetically heterogenous and may follow autosomal dominant, autosomal recessive, or X-linked recessive patterns of inheritance. It is characterized by night or dim light vision disturbance or delayed dark adaptation, poor visual acuity, myopia, nystagmus, strabismus, normal color vision and fundus abnormalities. Two forms of CSNB are recognized; complete CSNB1 and incomplete CSNB2. In CSNB2 disorder the b-wave responses are deficient and a-waves seem to be normal. Most CSNB2 patients do not complain of night blindness. Visual acuity is mildly to severely reduced. No treatment beyond correction of the refractive error is available but tinted lenses are sometimes used to enhance vision.
Khan et al (2013) found a homozygous CABP4 mutation in 11 patients with congenital retinal dysfunction. The patients aged between 2-26 years from four consanguineous Saudi families. The first family had four affected siblings, the second family had three affected siblings, the third family had two affected siblings and their mother, and the fourth family had an affected boy. All affected patients had congenital nystagmus, low vision that was considered stable and photophobia.