| refraction, ocular | Refraction of light effected by the media of the eye. It also includes the determination of the refractive state and refractive correction. (12 Dec 1998) |
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| angle of refraction | <optics> The angle that a ray leaving a refracting medium makes with a line drawn perpendicular to the surface of this medium. (05 Mar 2000) |
| refraction | <physics> Bending of waves as they pass from a medium having one refractive index to a medium (or region within a medium) having a different refractive index. (09 Oct 1997) |
| refraction, angle of | <microscopy> The acute angle between the normal to a refracting surface at the point of incidence, and the refracted ray. (05 Aug 1998) |
| static refraction | Refraction without accommodation. (05 Mar 2000) |
| double refraction | <microscopy> The refraction of light in two slightly different directions to form two rays or vector components. Each ray is polarized, and their vibration directions are perpendicular to each other. Furthermore, each ray has a different velocity, and therefore a different refractive index. See: birefringence. (05 Aug 1998) |
| dynamic refraction | Refraction of the eye during accommodation. (05 Mar 2000) |
| index of refraction | <physics> For a given wavelength, this is the ratio of the velocity of light in vacuum (c) to the velocity of light in a refractive material (for example, glass, plasma, etc.). (09 Oct 1997) |
| law of refraction | For two given media, the sine of the angle of incidence bears a constant relation to the sine of the angle of refraction. Synonym: Descartes' law, Snell's law. (05 Mar 2000) |
| accommodation, ocular | The dioptric adjustment of the eye (to attain maximal sharpness of retinal imagery for an object of regard) referring to the ability, to the mechanism, or to the process. It is the effecting of refractive changes by changes in the shape of the crystalline lens. Loosely, it refers to ocular adjustments for vision at various distances. (12 Dec 1998) |
| adaptation, ocular | The adjustment of the eye to variations in the intensity of light. Light adaptation is the adjustment of the eye when the light threshold is increased; dark adaptation when the light is greatly reduced. (12 Dec 1998) |
| albinism, ocular | Albinism affecting the eye in which pigment of the hair and skin is normal or only slightly diluted. The classic type is x-linked (nettleship-falls), but an autosomal recessive form also exists. Ocular abnormalities may include reduced pigmentation of the iris, nystagmus, photophobia, strabismus, and decreased visual acuity. (12 Dec 1998) |
| anterior ocular segment | That portion of the eye comprising the cornea, iris, lens, and their associated chambers and adnexa. (05 Mar 2000) |
| cardinal ocular movements | Eye rotations to the right and left, upward to the right and left, and downward to the right and left, to diagnose positions of gaze. (05 Mar 2000) |
| Ramsden's ocular | An eyepiece of a microscope, consisting of two planoconvex lenses with convexities turned to each other. (05 Mar 2000) |