| retinal cone | <ophthalmology, physiology> One of the two photoreceptor cell types in the vertebrate retina. In cones the photopigment is in invaginations of the cell membrane of the outer segment. Cones are less sensitive to light than rods, and are differentially sensitive to particular wavelengths of light and therefore important for colour vision. They provide vision with higher spatial and temporal acuity, and it is the combination of signals from cones with different pigments that facilitates colour vision. There are three types of cones, each type sensitive to red, green or blue. Present in large numbers in the fovea. (03 Jul 1999) |
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| retinal degeneration | <ophthalmology> A retrogressive pathological change in the retina, focal or generalised, caused by genetic defects, inflammation, trauma, vascular disease, or aging. Degeneration affecting predominantly the macula lutea of the retina is macular degeneration. (03 Jul 1999) |
| retinal dehydrogenase | An oxidoreductase catalyzing the interconversion of retinaldehyde and NAD+ to retinoic acid and NADH; thus affecting growth and differentiation. Synonym: retinaldehyde dehydrogenase. (05 Mar 2000) |
| retinal detachment | <ophthalmology> A painless disorder (when spontaneous) where the patient complains of a gradual raising or lowering of a curtain over the visual field of the affected eye. May also occur as the result of trauma. (27 Sep 1997) |
| retinal disease | <ophthalmology> A general term which describes any retinal changes (haemorrhages or exudates) that can affect vision (for example diabetic retinopathy, hypertensive retinopathy). (27 Sep 1997) |
| retinal disparity | The slight difference in retinal images that arises because of the lateral separation of the two eyes that stimulates stereoscopic vision. (05 Mar 2000) |
| retinal drusen | <ophthalmology> Colloid or hyaline bodies lying beneath the retinal pigment epithelium. They may occur either secondary to changes in the choroid that affect the pigment epithelium or as an autosomal dominant disorder of the retinal pigment epithelium. (12 Dec 1998) |
| retinal dysplasia | <ophthalmology> Congenital, often bilateral, retinal abnormality characterised by the arrangement of outer nuclear retinal cells in a palisading or radiating pattern surrounding a central ocular space. This disorder is sometimes hereditary. (12 Dec 1998) |
| retinal embolism | Embolism of an artery of the retina. (05 Mar 2000) |
| retinal fold | A congenital or secondary fold, consequent to membrane contraction, producing star-shaped, meridional, or circular fold's on the retina. (05 Mar 2000) |
| retinal ganglion cell | <pathology> A type of interneuron that conveys information from the retinal bipolar, horizontal and amacrine cells to the brain. (18 Nov 1997) |
| retinal ganglion cells | Cells of the innermost nuclear layer of the retina, the ganglion cell layer, which project axons through the optic nerve to the brain. They are quite variable in size and in the shapes of their dendritic arbors, which are generally confined to the inner plexiform layer. (12 Dec 1998) |
| retinal image | A real image formed on the retina. (05 Mar 2000) |
| retinal isomerase | <enzyme> Converts all-trans-retinal to 11-cis-retinal Registry number: EC 5.2.1.3 Synonym: retinal photoisomerase (26 Jun 1999) |
| retinal monooxygenase | <enzyme> Cytochrome p-450 and NADPH-dependent enzyme from rabbit liver microsomes Registry number: EC 1.14.13.- Synonym: retinoic acid synthase (26 Jun 1999) |