affects 1 in 3,000 individuals and affects between 50000 and 100000 people in the United States. Autosomal dominant RP accounts for approximately 15% of these cases. Autosomal dominant retinitis pigmentosa (ADRP) is a genetically heterogeneous group of inherited retinal degenerations that cause blindness in humans. RP begins with death of rod photoreceptor cells, which are the only cells in the retina to express rhodopsin and which express it as their most abundant protein. Eventually, loss of rod cells leads to loss of cone cells (cone photoreceptors), the mainstay of human vision. Symptoms of RP include loss of sensitivity to dim light, abnormal visual function, and characteristic bone spicule deposits of pigment in the retina. Affected individuals progressively lose visual field and visual acuity, and photoreceptor cell death can ultimately lead to blindness. A prominent early clinical feature of retinitis pigmentosa is the loss of night vision as a result of death of rod photoreceptor cells. Proper expression of the wild-type rhodopsin gene is essential for the development and sustained function of photoreceptor cells. Mutations in the human rhodopsin that affect its folding, trafficking and activity are the most commonly encountered causes of retinal degeneration in affected patients. A single base-substitution at the codon position 23 in the human opsin gene (P23H) is the most common cause of ADRP in American patients. ADRP due to rhodopsin mutations has a wide range of clinical presentation and severity. Before 1991, phenotypic evidence pointed to different subsets of ADRP with varying prognoses. Molecular classification of ADRP and further sub-classification based on the region of the mutation in the rhodopsin gene allowed better prediction of a particular disease course. But even within these specific subsets, the prognosis is influenced by the specific mutation itself. Rhodopsin and its function in vision Rhodopsin is the opsin of rod photoreceptor cells, which are the only cells in the retina that express rhodopsin and which express it as their most abundant protein. It is an integral part of the visual cascade. It is a G-protein-coupled receptor activated by light that initiates the phototransduction cascade (visual transduction cascade taking place in photoreceptor rod outer segments.) converting light signals to electrophysiological signals in retinal neurons. This photo-activated signal transduction process is essential for vision. The structure and function of rhodopsin and the gene encoding it have been the subjects of intense scrutiny for many years because rhodopsin serves as a useful