| exudative retinal detachment | Detachment of the retina without retinal breaks, arising from inflammatory disease of choroid, retinal tumours, and retinal angiomatosis. (05 Mar 2000) |
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| falciform retinal fold | A congenital fold from the disk to the ciliary region in the inferior temporal quadrant of the retina. (05 Mar 2000) |
| 11-cis-retinal | The isomer of retinaldehyde that can combine with opsin to form rhodopsin; it is formed from 11-trans-retinal by retinal isomerase. Synonym: neoretinal b. (05 Mar 2000) |
| Abbe theory of image formation | <optics, physics> Abbe's theory is based on the fact that a non-self-luminous particle, which is illuminated by an extraneous source, gives rise to diffracted light rays, in addition to the dioptric pencil. He stated that to form a good microscopical image as many of the diffracted rays as possible should be intercepted by the objective. With closely ruled lines, his theory is easily demonstrated by observing the back lens of the objective, for here the diffracted rays can be observed directly if the aperture diaphragm is closed. It can be shown that, when the illumination is arranged to exclude the diffracted images, resolution is lost. (11 Mar 1998) |
| accidental image | Continuation of visual impression after cessation of stimuli causing the original image. (12 Dec 1998) |
| body image | A term for the concept which each individual has of his own body as an object in and bound by space, independently and apart from all other objects. (12 Dec 1998) |
| radiographic image enhancement | Improvement in the quality of an X-ray image by use of an intensifying screen, tube, or filter and by optimum exposure techniques. Digital processing methods are often employed. (12 Dec 1998) |
| radiographic image interpretation, computer-assisted | Computer systems or networks designed to provide radiographic interpretive information. (12 Dec 1998) |
| real image | An image formed by the convergence of the actual rays of light from an object. Synonym: inverted image. (05 Mar 2000) |
| catatropic image | <ophthalmology, physiology> The two images formed by the anterior and posterior surfaces of the cornea and the two images formed by the anterior and posterior surfaces of the lens. Synonym: catatropic image, Purkinje images, Sanson's images. (05 Mar 2000) |
| virtual image | <microscopy> Such as seen in a mirror or through a magnifier. A virtual image has no real existence in space as does a real image from a lens. It does have a definite location, however, caused by the angles of divergence of the rays received by the eye. This can be shown by the common school experiment of placing a pin coincident with its mirror image behind a sheet of glass acting as a partial mirror. Its location can also be placed in design by extrapolating backwards to a focus. If a magnifier is used as it should be, with the object at its focus, the virtual image is at infinity. The same is true for a microscope focused for the relaxed eye. See: distance of virtual image. (05 Aug 1998) |
| visual image | A collection of foci corresponding to all the luminous points of an object. (05 Mar 2000) |
| mental image | A picture of an object not present, produced in the mind by memory or imagination. (05 Mar 2000) |
| phase image | A magnetic resonance image showing only phase shift information, to detect motion. (05 Mar 2000) |
| mirror image | A representation of an object or part thereof as its reflected image in a glass mirror. (05 Mar 2000) |