Glossary
Displaying 1-20 of 165 results.
Term | Definition | |
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Aberration | An unequal refraction or focalization of light rays. | ![]() |
Accommodative Astigmatism | Ocular astigmatism induced by alterations of the curvatures of the crystalline lens. See also Astigmatism. | ![]() |
Against-The-Rule Astigmatism | The flattest (longest) radius of corneal curvature lies vertically and the steepest (shortest) curve of the cornea is horizontal. This form of astigmatism has its greatest refractive power in the horizontal meridian. See also Astigmatism. | ![]() |
Alternating Multifocal Contact Lenses | This design has distinct zones in the lens for distance and near vision. When the user looks straight ahead they are using the distance portion of the lens. When looking down, correct lid interaction allows for near vision through the inferior portion of the lens. The near segment can be designed in a half-moon, crescent, or annular shape. Stabilization techniques use prism ballast or truncation. | ![]() |
Annular Multifocal Contact Lenses | See also Concentric Multifocal Contact Lenses. | ![]() |
Apical Bearing | A resulting fluorescein pattern where the posterior lens curvature lightly touches the corneal apex . | ![]() |
Apical Clearance | A resulting fluorescein pattern where the posterior lens curvature does not touch the corneal apex . | ![]() |
Apical Pooling | See also Apical Clearance. | ![]() |
Apical Touch | A resulting fluorescein pattern where the posterior lens curvature rests on the corneal apex . | ![]() |
Aspheric Lens | A lens design where one or both surfaces of the lens are non-spherical. An aspherical surface is designed to reduce various forms of optical aberrations. See also Aberration. | ![]() |
Aspheric Multifocal Contact Lenses | See also Simultaneous Multifocal Contact Lenses. | ![]() |
Astigmatism | A vision disorder that occurs when the cornea of the eye is uneven in shape. Astigmatism may also result from the irregular way the natural crystalline lens refracts light. Both causes result in light rays that focus at more than one point on the retina. | ![]() |
Axial Edge Lift | See also Edge Lift. | ![]() |
Back Optic Zone Diameter (BOZD) | Diameter of the central back optic zone measured by the surrounding junction. | ![]() |
Back Optic Zone Radius (BOZR) | The radius of curvature of the back optic zone; previously called the back central optic radius (BCOR) | ![]() |
Back Peripheral Radius (BPR) | The radius of curvature of the peripheral zone surrounding the central optic zone. | ![]() |
Back Peripheral Zone Diameter (BPZD) | The diameter of the back region surrounding the central optic zone. | ![]() |
Back Surface Toric | Lens design where part or the entire posterior surface of the lens is of a toric construction. See also Toric Lens. | ![]() |
Bandage Contact Lens | A soft contact lens worn to protect or treat a diseased or injured cornea. | ![]() |
Bi-Aspheric | Lens design where the posterior surface of the lens consists of two different aspheric curves. See also Aspheric Lens. | ![]() |
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