Retinitis pigmentosa: fundus camera image showing the degeneration of the retina, the light- sensitive layer of the eye due to retinitis pigmentosa. The pattern of dark spots across the retina corresponds to the extent of loss of vision. The first symptom is usually an awareness that vision is poor in low light. Sight testing reveals a ring-shaped area of blindness, that progresses to involve an increasing area of the visual field. The central retina (in the region of the macula) is more resistant & so central vision may be retained, often for many years. Retinitis pigmentosa usually has a genetic basis.