Diffuse Photoreceptor Dystrophies
Inherited dystrophies that affect the rods and cones are discussed in greater detail in BCSC Section 12, Retina and Vitreous. Only the most common photoreceptor dystrophy, retinitis pigmentosa (RP), is discussed here.
RP refers to a group of inherited retinal diseases characterized by RPE and photoreceptor dysfunction and degeneration, resulting in progressive visual field loss. The genetics of RP are complex: it can be sporadic, autosomal dominant, autosomal recessive, or X-linked. Mutations in the rhodopsin gene (RHO) are the most common cause of autosomal dominant RP.
The term retinitis pigmentosa is a misnomer because clear evidence of inflammation is lacking. Ophthalmoscopic findings include pigment arranged in a bone-spicule–like configuration around the retinal arterioles, arteriolar narrowing, and optic nerve head atrophy (Fig 11-40A). The disease is characterized primarily by the loss of rod photoreceptor cells via apoptosis. Cones are seldom directly affected; however, they degenerate secondary to the loss of rods. Microscopically, loss of photoreceptor cells is seen, as well as RPE migration into the neurosensory retina around retinal vessels (Fig 11-40B). The arterioles, though narrowed clinically, show no histologic abnormality initially. Later, thickening and hyalinization of the vessel walls develop. The optic nerve may show diffuse or sectoral atrophy, with gliosis as a late change.
Excerpted from BCSC 2020-2021 series: Section 4 - Ophthalmic Pathology and Intraocular Tumors. For more information and to purchase the entire series, please visit https://www.aao.org/bcsc.