['To inform ophthalmologists of the extraordinary progress in molecular genetics that is revolutionizing our understanding of ophthalmic disease and of the crucial role of the clinician in facilitating genetic discovery.', 'Review of relevant articles.', 'Genes for many mendelian-inherited eye diseases have been localized and some identified using three general approaches: positional cloning, which requires no knowledge of underlying pathophysiology; a candidate gene approach, which examines genes based on their likely function; and a positional candidate approach, which uses map location as well as candidate genes in the linked region to isolate a gene. In positional cloning, once linkage is obtained, the gene can eventually be isolated, cloned, and sequenced and mutations identified. Techniques in molecular biology and other disciplines can then be used to unravel the pathophysiology of a disease.'] Is molecular genetics revolutionizing our understanding of ophthalmic disease?