retinal

[RETIN(OL) + AL(DEHYDE).]

1. pertaining to the retina.
2. the aldehyde of retinol, having vitamin A activity. One isomer(11-cis-retinal) combines with opsin in the retinal rods (scotopsin) to form rhodopsin (visual purple); another, all-trans-retinal, or visual yellow, results from the bleaching of rhodopsin by light, in which the 11-cis-form is converted to the all-trans-form. Retinal also combines with opsins in the retinal cones to form the three pigments responsible for color vision.

• r. absence — inherited as a recessive character in foals.
• central progressive r. atrophy — a disease of the retinal pigmented epithelium, generally in middle-aged Labrador retrievers, Border collies, Golden retrievers, Irish setters, and English springer spaniels. There are pigmentary changes in the tapetal fundus, with attenuation of retinal vasculature, and atrophy of the optic disk. Day vision is affected first, followed by impairment, but not always blindness, in any situation. Called also CPRA.
• r. degeneration — see progressive retinal atrophy (below), bright blindness, taurine nutritional deficiency, retinopathy.
• r. detachment — see retinal detachment.
• r. dialysis, r. disinsertion — separation of the sensory retinal layer from the pigment layer at the ora ciliaris retinae.
• r. dysplasia — a congenital anomaly in many species, consisting of an abnormal differentiation of retinal cells and proliferation of photoreceptors, forming rosettes. May be caused by viral infections such as feline panleukopenia, bluetongue, bovine virus diarrhea and canine herpesvirus; an inherited defect in some breeds of dogs and cattle.
• r. ganglionic cell layer — the layer of the retina which contains ganglion cell bodies.
• r. hemorrhages — occur in association with many systemic diseases and intoxications in most species, including ethylene glycol poisoning, ehrlichiosis, severe anemia and thromboembolic meningoencephalitis in cattle.
• inner r. nuclear layer — the layer of the retina which contains the cell bodies of bipolar neurons and association neurons.
• light-induced r. degeneration — a phototoxic degeneration in rats and mice caused by exposure to continuous light and high temperatures.
• r. nuclear layer — the layer of the retina which includes inner and outer nuclear layers of the retina.
• r. optic nerve fiber layer — retinal layer of axonal processes of the ganglion cells as they approach the optic papilla and emerge as the optic nerve.
• outer r. nuclear layer — the layer of the retina which contains the cell nuclei of the photoreceptor cells.
• r. photoreceptor layer — the retinal layer which contains rods and cones, modified neuronal processes of the photoreceptor rod and cone cells.
• r. pigment epithelial layer — retinal layer just beneath the choroidal basal complex of the eye; probably serves as a store of vitamin A. Long cellular processes extend to and between the photoreceptor cells in the next layer.
• r. plexiform layer — the retinal layer which includes inner and outer plexiform layers; both consist of a network of cell processes of adjacent nerve cells, especially photoreceptor and ganglion cells.
• progressive r. atrophy — a group of inherited, degenerative diseases of the retina, occurring most commonly in dogs and consisting of a progressive, noninflammatory degeneration or dysplasia of rods and cones or purely cones, leading to blindness. Specific features, such as age of onset, pattern of degeneration, and ultrastructural and biochemical changes vary between the many breeds in which the disease is found. Night blindness followed by a loss of day vision are clinical signs common to most. There may also be an associated cataract formation. See also central progressive retinal atrophy (above), cone dysplasia, rod–cone dysplasia. Called also PRA.
• progressive r. degeneration — in one system of classification, a term encompassing a range of retinal disorders otherwise referred to as various types of retinal atrophy, retinal dysplasias or retinal degenerations. The inherited rod–cone dysplasias of dogs and cats are included in Type I; pigment epithelial dystrophy (central progressive atrophy) is Type II; and hemeralopia of Alaskan malamutes and miniature poodles is Type III. Called also PRD.
• sudden acquired r. degeneration — a nonspecific degeneration of rods and cones that progresses to complete retinal atrophy and blindness in mature dogs. The cause is unknown. Called also silent retina syndrome, metabolic toxic retinopathy, SARD.

The noun has one meaning:

Meaning #1: either of two yellow to red retinal pigments formed from Rhodopsin by the action of light
  Synonym: retinene

The adjective retinal has one meaning:

Meaning #1: in or relating to the retina of the eye
  Pertains to noun: retina (meaning #1)