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How does retinitis pigmentosa affect rods and cones over time?
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Photoreception
The mammalian eye has a cornea and a lens and functions as a dioptric system, in which light rays are refracted to focus on the retina.
Retinitis pigmentosa is a group of hereditary eye diseases characterized by the progressive degeneration of the retina. The disease typically follows a specific pattern of photoreceptor loss:
- Early Stage: The rod cells—photoreceptors responsible for vision in dim light—are destroyed early in the course of the disease. This initial degeneration manifests as night blindness, often appearing in youth.12
- Progression: Over time, the disease involves further retinal atrophy and changes in the pigment epithelium. As the condition advances, cone cells—which mediate daytime and color vision—are also destroyed, leading to the loss of daytime vision.12
Commonly, this progressive loss of photoreceptors results in a constriction of the visual field, often described as tunnel vision. While the course of the disease is generally very slow, it leads to severe visual impairment. Genetic mutations, including those affecting the rhodopsin protein, are known to be responsible for various forms of the condition.132