retina

retina (ret´i-na) [NA]

Grossly, the r. consists of three parts: optic part of retina, ciliary part of retina, and iridial part of retina. The optic part, the physiologic portion that receives the visual light rays, is further divided into two parts, pigmented part (pigment epithelium) and nervous part, which are arranged in the following layers: 1) pigment epithelium; 2) layer of rods and cones; 3) external limiting lamina, actually a row of junctional complexes; 4) external nuclear lamina; 5) external plexiform lamina; 6) internal nuclear lamina; 7) internal plexiform lamina; 8) ganglionic cell lamina; 9) lamina of nerve fibers; 10) internal limiting lamina. Layers 2 through 10 comprise the nervous part. At the posterior pole of the visual axis is the macula, in the center of which is the fovea, the area of acute vision. Here layers 6, 7, 8, and 9 and blood vessels are absent, and only elongated cones are present. About 3 mm medial to the fovea is the optic disk, where axons of the ganglionic cells converge to form the optic nerve. The ciliary and iridial parts of the r. are forward prolongations of the pigmented layer and a layer of supporting columnar or epithelial cells over the ciliary body and the posterior surface of the iris, respectively.tunica interna bulbi [NA], nervous tunic of eyeball, optomeninx; [Mediev, L. prob. fr. L. rete, a net]
albedo r.'s obsolete term for a white area of the retina due to edema or infarction.
coarctate r. obsolete term for a ringlike effusion of fluid between the choroid and r., giving the latter a funnel shape.
detached r. retinal detachment
flecked r. an r. exhibiting fundus flavimaculatus, hereditary drusen, or fundus albipunctatus.
fleck r. of Kandori [MIM*228990] an autosomal-recessive disorder of the retinal pigment epithelium occurring among Japanese.
leopard r. tessellated fundus
shot-silk r. the appearance of numerous wavelike, glistening reflexes, like the shimmer of silk, observed sometimes in the r. of a young person.shot-silk phenomenon, shot-silk reflex;
tigroid r. tessellated fundus

 

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