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X-linked Retinoschisis is a leading cause of juvenile macular degeneration. Four Western Australian families affected by X-Linked Retinoschisis were analysed using DNA and clinical information from the Australian Inherited Retinal Disease (IRD) Register and DNA Bank. By direct sequencing of the RS1 gene, three genetic variants were identified; 52+1G > T, 289T > G and 416delA. 289T > G has not been previously reported and is likely to cause a substitution of a membrane binding residue (W92G) in the functional discoidin domain. All clinically diagnosed individuals showed typical electronegative ERGs. The 52+1G > T obligate carrier also recorded a bilaterally abnormal rod ERG and mildly abnormal photopic responses. mfERG trace arrays showed reduced response densities in the paramacular region extending futher temporally for each eye.

Human congenital stationary night blindness (CSNB) is a group of non-progressive retinal dystrophies characterized by night blindness from birth and other symptoms such as myopia, hyperopia, reduced visual acuity and occasionally accompanied by nystagmus, and optic disc hypoplasia (Heonand and Musarella, 1994). CSNB can be inherited on autosomal dominant, autosomal recessive and X-linked recessive mode. According to the clinical and genetic studies, X-linked recessive CSNB (XLCSNB) can be divided into two subtypes: complete (CSNB1; MIM 310500) and incomplete (CSNB2; MIM 300710). The distinction between the two subtypes of XLCSNB is in electroretinogram (ERG) and in genetic basis. CSNB1 is characterized by the complete absence of the rod b-wave, but almost normal cone amplitudes, while CSNB2 is associated with a reduced rod activity and a significantly abnormal cone ERG. The disease gene responsible for CSNB2 (CACNA1F) at Xp11.23 encodes a retina-specific L-type calcium channel α-subunit. CSNB1 results from mutations in the NYX (nyctalopin on chromosome X) gene at Xp11.4 (Miyake et al., 1986; Bech-Hansen et al., 1998). We describe a Chinese family with multiple individuals affected with reduced vision and high myopia, which has been misdiagnosed as “pathologic myopia and amblyopia”. Clinical and genetic investigation indicated a phenotype of CSNB1. Linkage analysis for the family mapped this phenotype to Xp11.4. Sequencing of NYX identified one novel mutation.