| refractive index | <microscopy> The ratio of the velocity of light in a vacuum to the velocity in some medium. Refractive index generally increases with the atomic number of the constituent atoms. (05 Aug 1998) |
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| refractive | Serving or having power to refract, or turn from a direct course; pertaining to refraction; as, refractive surfaces; refractive powers. Refractive index. <medicine> The ratio of the sine of the angle of incidence to the sine of the angle of refraction for a ray passing out of one of the media into the other. Origin: Cf. F. Refractif. See Refract. Source: Websters Dictionary (01 Mar 1998) |
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| refractive accommodative esotropia | That type of esotropia eliminated by correction of hypermetropic refractive error. (05 Mar 2000) |
| refractive amblyopia | A suppression of central vision due to an unequal refractive error (anisometropia) of at least two diopters. This induces a sufficient difference in image size (aniseikonia) that the two images cannot be fused. In order to avoid confusion, the blurrier image is suppressed. Synonym: refractive amblyopia. (05 Mar 2000) |
| refractive errors | Deviations from the average or standard indices of refraction of the eye through its dioptric or refractive apparatus. (12 Dec 1998) |
| refractive keratoplasty | Any procedure in which the shape of the cornea is modified, with the intent of changing the refractive error of the eye; for example, if the cornea is flattened, the eye becomes less myopic. See: photorefractive keratectomy, keratophakia, lamellar keratoplasty, thermokeratoplasty, keratomileusis, radial keratotomy. Synonym: keratorefractive surgery. (05 Mar 2000) |
| refractive keratotomy | Modification of corneal curvature by means of corneal incisions to minimise hyperopia, myopia, or astigmatism.In this type of radial keratotomy surgery, performed by excimer laser, pie-shaped pieces of cornea are removed under local anaesthetic. The resulting scar tissue formation reshapes the cornea. This class of surgery is somewhat unpredictable, and its long-term effects are still unknown. (05 Mar 2000) |
| absorbancy index | Absorbance (of light) per unit path length (usually the centimeter) and per unit of mass concentration. Compare: molar absorption coefficient. Synonym: absorbancy index, absorptivity, extinction coefficient, specific extinction. (05 Mar 2000) |
| alveolar index | Relation between the basialveolar (basion to alveolar point) and basinasal (basion to nasion) lengths: (basialveolar length × 100)/basinasal length; the result indicates the degree of projection of the maxilla or upper jaw. Synonym: alveolar index. (05 Mar 2000) |
| anaesthetic index | Ratio of the number of units of anaesthetic required for anaesthesia to the number of units of anaesthetic required to produce respiratory or cardiovascular failure. (05 Mar 2000) |
| antitryptic index | An obsolete term for the relative retardation in loss of viscosity of a solution of casein incubated with trypsin, to which a drop of abnormal blood serum (as from a cancerous patient) has been added, compared with that in a similar solution to which normal serum has been added; if the former drips through the tube of the viscosimeter in 100 seconds, and the latter in 104 seconds, the antitryptic index is 4. (05 Mar 2000) |
| Arneth index | An expression based on adding the percentages of polymorphonuclear neutrophils with 1 or 2 lobes in their nuclei, plus one-half the percentage with 3 lobes; the normal value is 60%. See: Arneth formula, Arneth count. (05 Mar 2000) |
| auricular index | Relation of the width to the height of the auricle or pinna: (width of pinna × 100)/length of pinna. (05 Mar 2000) |
| Ayala's index | The cerebrospinal index when 10 ml of cerebrospinal fluid have been removed. Synonym: Ayala's quotient, spinal quotient. (05 Mar 2000) |
| basilar index | Ratio between the basialveolar line and the maximum length of the cranium, according to the formula: (basialveolar line × 100)/length of cranium. Synonym: alveolar index. (05 Mar 2000) |
| Bodecker index | A modification of the DMF caries index. (05 Mar 2000) |