Hereditary retinochoroidal dystrophies. Part 2: differential diagnosis

A generally accepted classification for inherited retinochoroidal dystrophies does not exist. The names given to certain disorders are either based on ophthalmoscopic findings, or on histologic, electrophysiologic and genetic findings. Future research on the molecular genetic background will result in better definition of clinical entities. The purpose of this project is to outline a practical approach to inherited retinochoroidal dystrophies. For this reason, disorders with similar clinical symptoms are grouped together. Generalized retinochoroidal dystrophies affecting all retinal areas can be distinguished from regional dystrophies. Generalized dystrophies can be subdivided into those with peripheral onset, usually associated with initial rod function loss (night blindness, peripheral field loss: e.g. retinitis pigmentosa, choroideremia) and those with central onset associated with cone function loss (visual acuity loss, central scotoma, color vision deficits: e.g. cone or cone-rod dystrophies). Regionally limited dystrophies include the multitude of macular dystrophies and the autosomal dominant vitreoretinochoroidopathy, which remains limited to the periphery. It is important for a differential diagnosis to exclude involvement of other organ systems in syndromic disorders. Stationary inherited retinal dysfunction (e.g. monochromatism, congenital stationary night blindness) and other inherited or acquired diseases have to be excluded as well. Guidelines for differential diagnosis are presented.