Some hereditary induced disorders affect primarily a single layer of the retina. Others such as retinitis pigmentosa (right) commence in one layer, the pigment epithelium, but soon include all layers equally.
Retinitis pigmentosa (RP) is the applicable ocular terminology when patients develop night blindness in young adulthood, progressive contraction in the peripheral field with preservation of central vision, and profound visual loss in later life. The degenerative process commences in the pigmented layer of the retina. Dark, bone-like spicules develop at the equatorial level and, over time, encroach posteriorly toward the macula. Sometimes swelling develops within the central retina, and if so, dietary salt restriction to the 1000 mgm level (for sodium) is indicated. Dominant RP inheritance causes less severe retinal changes (atrophy) and a less profound reduction in visual perception.