A measure of the degree to which light is dispersed when entering a lens. the average range is 20 to 60. a lower abbe value causes greater dispersion of light resulting in chromatic aberration (co...
A convergence response (to turn the eyes inward) which occurs as a direct result of accommodation (eye focusing). achromatism- the ability of the eye to adjust the focal power to see objects at di...
- The ability to respond to faint sense impressions or to distinguish light differences between stimuli. adaptation/adaptive process – the maneuvers (conscious or unconscious, automatic or volun...
- Inward movement of the eye medially.
- The movement of a part of the body towards the midline or towards a neighbouring part. compare abduction. see illustration at anatomical terms i...
|adjustable nose pads|
Type of bridge that consists of small pads made of plastic or silicone to help prevent slippage and aid in evenly distributing weight of glasses on bridge of the nose.
Nerve fibers which carry impulses from the organs to the nerve centers.
Ability of the eye to retain sight of an image during eye blinks. the most common example is seeing light after the flash of a camera.
Objects sighted through convex (plus) lenses move in an opposite (against) direction as the convex lenses are moved from side to side.
The strengthening of a lens as a result of cooling a heated lens.
- Pigmentation is deficient or absent. may occur in skin, hair, and eyes. ocular albinism is a pigmentation deficiency occurring mainly in the eyes. individuals with albinism including ocular al...
- Eye disorders that prevent a clear image from forming on the retina (myopia, hyperopia, astigmatism). amblyopia exanopsia (lazy eye) – uncorrectable blurred vision due to a lack of use; the vi...
A 21-point optometric examination. each point is a measurement of performance of a visual behavior pattern. these measurements, made through the application of prism and sphere, show the absorptio...
The image of an object as seen by one eye is different in size and shape from the other one.
- Unequal different refractive errors of the two eyes. annealing - the heating of a material to a sufficiently high temperature with subsequent controlled cooling to relieve any internal stress ...
The space in front of the iris and behind the cornea, which includes cornea, conjunctiva, iris, lens and aqueous humor.
One eye myopic (near sighted), the other hyperopic (far sighted).
A multi-layer thin coating applied to the lens surface to reduce the amount of reflection from the lens and increase light transmission.
- A condition caused by the removal of the crystalline lens most often due to cataracts.
- The absence of the crystalline lens in the eye
A clear watery liquid in the chamber of the eye that flows between the cornea and the crystalline lens and nourishes both; secreted by the ciliary processes.
Combined layers making up an ar coating (usually five or more). composition of layers can vary between ar coaters.
- Free from, absence of infection or infectious material.
- The absence of microorganisms which cause infection, usually achieved by sterilisation
A lens that is not spherical. the lens surface is marked by a variety of elliptically changing curvatures. an aspheric design allows a lens to be much flatter without compromising the optics of th...
|aspheric compensation of power|
Power is compensated in each area of the lens by applying aspheric principles.
- Symptoms of “eye-strain” including headaches, tearing, itching, burning, and blurred vision.
- Same as eyestrain
A lens design that has contour line patterns positioned differently into the nasal and temporal area to produce a right and left lens design. this is eye specific so the lens can not be rotated to...
Lens with astigmatic power in which at least one principal meridian is not spherical.
This method determines the eye’s refractive error and the best corrective lenses to be prescribed by using a computerized device that varies its optical power mechanically and prints out the resul...
|axis aligner plier|
Any device used for aligning a cylinder axis of a spectacle lens at its proper angle.
That principal meridian which contains only the spherical power component of a sphero-cylinder lens. axis will intersect a spherical lens of minus power at its thinnest point and a spherical plus ...
|axis indicator of lensometer|
A device in which a scale from 0? to 180? can be aligned to give the axis of cylinder power on a spectacle lens. b “b” box measurement – in lens measurement, the longest vertical distance from the...
A lens placed in a frame which looks like the lens for the opposite eye to balance cosmetics; similar in thickness and style with no specific rx power.
Commonly used for a type of crown glass, one of the ingredients is barium oxide added for the purpose of increasing refractive index, while maintaining relatively low dispersion. barrel - (bbl) – ...
A type of glass containing lead for increasing the index together with barium to increase refractive index, while maintaining a relatively low dispersion.
The singular dioptric curve on the front surface of a lens. this curve is generally in place when the lens blank is manufactured and as such will control the selection of back curves necessary to ...
The subjective; it is the lens power that alters the light rays entering an eye and causes a change in the focusing mechanism in the greatest degree without causing a subjectively detected alterat...
Used to check the specific gravity of a polishing solution.
A machine by which an uncut lens is given a bevel on its edge by a special lens grinding wheel. bi-centric grinding (slab off) – the process of grinding base up prism to correct vertical imbalance...
A lens style where both front and back surfaces are minus (concave). двояковогнутый;
A lens style where both the front and back surfaces are plus (convex). двояковыпуклый;
A lens with two focal points, one for distance vision and one for near. regular bifocals have a line between the prescriptions; progressive bifocals change gradually from the near to far prescript...
The single measured distance from pupil center to pupil center. binocular (binocularity) vision – the blending of the separate images by each eye into a single image; allows images to be seen with...
Using both eyes, but not together as a team.
Type of lens aberration that is induced during the manufacturing process which results in chromatic aberration. a rainbow-like effect (sometimes called newton rings).
A lens, both surfaces of which are ground and polished, in toric or cylindrical form. blank, molded – a lens blank that is unfinished on both sides when it arrives from the lens factory. blank, se...
A process to remove the tint from a dyed lens. выщелачивать;
A round style bifocal type lens designed so that there is no discernable line of demarcation between the distance portion and the reading portion. the blended area is visually nonusable.
Lenses have a full field curved or plano front surface with a high minus bowl-shaped surface on the ocular side surrounded by a plano surface called a carrier.
- A condition that describes an inflammation of the eyelid margins characterized by a sticky crust that forms on the eyelids.
- Inflammation of the eyelid
Reflected glare caused by light reflected off smooth, shiny surfaces blocking vision.
An orange colored tint formulated to block out ultraviolet radiation and reduce blue light which may be harmful to the eye.