| TGA | taurocholate gelatin agar; thyroglobulin activity; total glycoalkaloids; total gonadotropin activity... |
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| AVC | aberrant ventricular conduction; Academy of Veterinary Cardiology; aortic valve closure; associative... |
| VC | color vision; variance cardiography; vascular changes; vasoconstriction; vena cava; venereal case; v... |
| VDT | vibration disappearance threshold; visual display terminal; visual distortion test |
| VI | Roman numeral six; vaginal irrigation; variable interval; vastus intermedius; virgo intacta; virulen... |
| visual acuity | <microscopy> The ability to detect fine details or small distances with the eye. Visual acuity can vary substantially depending on the definition used and method of measurement chosen. Under favourable conditions, the resolution of the human eye or ability to distinguish the twoness of adjoining lines, is about I minute of arc while the threshold delectability, or the detection of misaligned steps in a line (which is also a form of visual acuity), can be as low as a fraction of a second of arc. (05 Aug 1998) |
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| visual agnosia | The inability to recognise objects by sight; usually caused by bilateral parieto-occipital lesions. Synonym: optic agnosia. (05 Mar 2000) |
| visual angle | The angle formed at the retina by the meeting of lines drawn from the periphery of the object seen. (05 Mar 2000) |
| visual aphasia | <neurology> Loss of the ability to understand printed words or sentences (27 Sep 1997) |
| visual area | Area of the occipital lobe concerned with vision. (12 Dec 1998) |
| visual axis | The straight line extending from the object seen, through the centre of the pupil, to the macula lutea of the retina. Synonym: line of vision. (05 Mar 2000) |
| visual blackout | See: amaurosis fugax. (05 Mar 2000) |
| visual cortex | Area of the occipital lobe concerned with vision. (12 Dec 1998) |
| visual cycle | The transformation of carotenoids involved in the bleaching and regeneration of the visual pigment. (05 Mar 2000) |
| visual efficiency | A rating used in computing compensation for industrial ocular injuries, incorporating measurements of central acuity, visual field, and ocular motility. (05 Mar 2000) |
| visual evoked potential | Voltage fluctuations that may be recorded from the occipital area of the scalp as the result of retinal stimulation by a light flashing at 1/4-second intervals; commonly summated and averaged by computer. (05 Mar 2000) |
| visual extinction | A condition in which individual stimuli are seen correctly, but when the nasal visual field of one eye and the temporal visual field of the fellow eye are stimulated simultaneously, one field is blind. Synonym: visual extinction. (05 Mar 2000) |
| visual field | The area simultaneously visible to one eye without movement; often measured by means of a bowl perimeter located 330 mm from the eye. (05 Mar 2000) |
| visual field test | <ophthalmology> A test which measures the extent of visual field loss. This test may be performed by a number of methods including confrontation, tangent screen exam and automated perimetry. Diseases that affect visual field include stroke, diabetes, hypertension, multiple sclerosis, glaucoma, hyperthyroidism, Jacob-Creutzfeldt disease and optic glioma. (27 Sep 1997) |
| visual image | A collection of foci corresponding to all the luminous points of an object. (05 Mar 2000) |