Investigation of retinitis pigmentosa

Retinitis pigmentosa is a solitary manifestation of separate genetically determined disorders in which there is progressive loss of vision and the appearance of characteristic fundus abnormalities. It is likely that each disease contained within this family of disorders has a different aetiology, a consideration which is important to the clinician, the researcher and the therapist. To the clinician it is essential to be able to identify the inheritance of the disorder in order to give educated genetic advice. It is the responsibility of the clinician to sub-divide retinitis pigmentosa into purer samples of disease since without such a sub-division research is unlikely to be fruitful. It is unreasonable to expect a biochemist to define systemic biochemical abnormalities if blood is analysed from a series of patients, each of which has a different disorder. If the cause of retinal degeneration in an animal homologue of human retinitis pigmentosa is identified the question is then raised as to whether the abnormality is relevant to human disease and, if so, to which one. Moreover, if a metabolic abnormality is identified in one disease it will not necessarily to be found in others and similarly, if therapy is effective in one form of the disease it may not be effective for all patients. A sub-division of retinitis pigmentosa may be made on the basis of inheritance of the disorder, on the basis of morphologic changes in the fundus, and on the qualitative functional changes identified. Such observations may also give some clues as to the pathogenesis of the different forms of RP or at least indicate in which cell system the primary disorders lie and will also show in what way the defect interferes with cell function. In this paper it is hoped to show that studies undertaken by the various disciplines within ophthalmology have now made limited achievements towards the goals of subdividing retinitis pigmentosa (RP) into purer samples of disease and typifying the functional and morphological attributes of the constituent disorders.