| visual purple | <protein> Light sensitive pigment formed from retinal linked through a Schiff's base to opsin: rhodopsin is an integral membrane protein found in the discs of retinal rods and cones, comprising some 40% of the membrane. Vertebrate opsins are proteins of 38 kD. See: bacteriorhodopsin. (18 Nov 1997) |
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| visual receptor cells | The rod and cone cell's of the retina. (05 Mar 2000) |
| visual-spatial agnosia | The inability to localise objects or to appreciate distance, motion, and spatial relationships; caused by lesion in the occipital lobe. Compare: simultanagnosia. (05 Mar 2000) |
| visual threshold | Threshold of visual sensation, the minimal light intensity evoking a visual sensation. Synonym: achromatic threshold, minimum light threshold. (05 Mar 2000) |
| visual violet | A visual pigment, composed of 11-cis-retinal bound to an opsin, found in the cones of the retina. Synonym: visual violet. Origin: G. Ion, violet, + ops, eye, + -in (05 Mar 2000) |
| visual yellow | The orange retinaldehyde resulting from the action of light on the rhodopsin of the retina, which converts the 11-cis-retinal component of the rhodopsin to all-trans-retinal plus opsin. Synonym: trans-retinal, visual yellow. (05 Mar 2000) |
| primary visual area | Area of the occipital lobe concerned with vision. (12 Dec 1998) |
| primary visual cortex | See: visual cortex. (05 Mar 2000) |
| secondary visual area | Area of the occipital lobe concerned with vision. (12 Dec 1998) |
| secondary visual cortex | See: visual cortex. (05 Mar 2000) |
| evoked potentials, visual | The electric response evoked in the cerebral cortex by visual stimulation or stimulation of the visual pathways. (12 Dec 1998) |
| unformed visual hallucination | Hallucination composed of sparks, lights, or bursting spheres of light. (05 Mar 2000) |
| formed visual hallucination | <psychiatry> Hallucination composed of scenes, often landscapes. (05 Mar 2000) |
| functional visual loss | An apparent loss of visual acuity or visual field with no substantiating physical signs; often due to a natural concern about visual loss combined with suggestibility and a fear of the worst; best treated with reassurance. (05 Mar 2000) |