front 1 Accommodation | back 1 Adjustment by the eye for seeing at different distances, accomplished by changing the shape of the crystalline lens through action of the ciliary muscle. |
front 2 Acuity | back 2 Clearness; visual acuity is measured by the smallest object that can be seen at a certain distance. |
front 3 Adnexa Oculi | back 3 Accessory structures of the eye, such as the lacrimal apparatus and the eyelids. |
front 4 Afterimage | back 4 Image of an object that persists when the lids are closed. |
front 5 Annular Bifocal Contact | back 5 A lens with distance portion ground into the center of the lens and the near portion ground into the periphery. |
front 6 Aphakic Lenses | back 6 Lenses designed for post cataract fitting. |
front 7 Apical Zone of Cornea | back 7 The central portion of the cornea with a constant radius of curvature. Also called the corneal cap. |
front 8 Artificial Tears | back 8 Wetting agent for the cornea to supplement the loss of tear formation. |
front 9 Aspheric Lens | back 9 A lens which is not spherical in shape. The curvature gradually flattens as the periphery is approached. |
front 10 Astigmatism | back 10 A refractive error that prevents the light rays from coming to a single focus on the retina because of different degrees of refraction in the various meridians of the eye. |
front 11 Against-The-Rule Astigmatism | back 11 A condition in which the steepest corneal meridian is in the horizontal plane. An example of Keratometer readings for a patient exhibiting against-the-rule astigmatism would be: K’s 45.00@180/42.00@90. |
front 12 Irregular Astigmatism | back 12 Astigmatism caused by an irregularly shaped cornea. This can occur in conditions such as Keratoconus or corneal scarring. This type of astigmatism cannot be corrected by cylinders. |
front 13 Lenticular Astigmatism | back 13 Astigmatism that is found in the crystalline lens. Lenticular astigmatism is present when there is significantly more astigmatism in the patient's refraction (cylinder power in Rx) than on their corneal surface (difference in K-readings). |
front 14 Oblique Astigmatism | back 14 Regular astigmatism in which the principle meridians are other than 90 and 180. |
front 15 Residual Astigmatism | back 15 Astigmatism remaining after the corneal astigmatism has been neutralized. |
front 16 With-The-Rule Astigmatism | back 16 Condition in which the steepest corneal meridian is in the vertical plane. An example of Keratometer readings for a patient exhibiting with-the- rule astigmatism would be: K’s 42.00@180/45.00@90. |
front 17 Bactericide | back 17 A chemical that disinfects and kills pathogenic organisms. |
front 18 Benzalkonium Chloride | back 18 A preservative used in rigid contact lens solutions because of its germicidal qualities. |
front 19 Biomicroscopy | back 19 A method of examining the cornea under a magnification of from 10 to 50 times utilizing a slit lamp. |
front 20 Burton Lamp | back 20 An ultraviolet light used to illuminate the fluorescein dye that is used to analyze the fit of a rigid contact lens. |
front 21 Canthus | back 21 The angle at either end of the slit between the eyelids; specified as outer (temporal) and inner (nasal). |
front 22 Chord Length | back 22 The straight line measurement of the contact lens diameter from edge to edge. |
front 23 Contact Lens Wetting Angle | back 23 The angle between the liquid and the lens surface. |
front 24 Contour Lens | back 24 A tricurve lens designed to conform to the curvature of the cornea, which flattens as it extends in the periphery. |
front 25 Copolymer | back 25 Two or more chemicals that are combined to form a new chemical compound. |
front 26 Corneal Cap | back 26 The apical zone or central zone of the cornea that has a constant area of curvature. |
front 27 Corneal Diameter | back 27 The diameter of the cornea, usually taken along the horizontal meridian with a ruler. Also called visible iris diameter. |
front 28 Deturgence, Corneal | back 28 The state of relative dehydration maintained by the normal intact cornea that enables it to remain transparent. |
front 29 Diagnostic Fitting Set | back 29 A set of trial lenses used to gain an overview of the fit of a contact lens. |
front 30 Disinfection | back 30 Physical or chemical procedures that kill common pathogenic organisms but may permit some nonpathogenic organisms to survive. |
front 31 DK Value | back 31 A measure of the oxygen permeability through a given material where D is the diffusion coefficient for oxygen movement on the lens material and K is the solubility of oxygen in this material. |
front 32 Double Slab-Off Lenses | back 32 Sometimes called thick-thin lenses; the upper and lower portions of the lens are reduced in thickness so that when the lens is placed on the eye these portions lie under the upper and lower eyelids. The thin zones aid in stabilizing toric soft lenses. |
front 33 Dry Spots | back 33 Areas of drying as noted by absent areas of fluorescein-stained tear film on the cornea when the patient stares. |
front 34 Dyer Nomogram System of Lens Ordering | back 34 A simplified system of ordering rigid lenses based on clinical experience, corneal topogometry, and charts of associated lens parameters. |
front 35 Enzyme Cleaner | back 35 A cleaning agent that acts on a soft lens by a digestion of protein. |
front 36 Esthesiometer (Cochet-Bonnet) | back 36 A device used to evaluate corneal sensitivity, consisting essentially of a nylon thread mounted in a handle so that its length may be varied and calibrated in milligrams of weight necessary to bend a given length of the thread when pressed against the cornea. |
front 37 Fissure | back 37 Elliptic space between the eyelids. |
front 38 Finished Lens | back 38 A complete lens with anterior and posterior curves, a specified diameter, a designated peripheral curve, and edge design. |
front 39 Fitting Set | back 39 A complete inventory of lenses of graduated powers and base curves. |
front 40 Flare | back 40 Flutterings or fringing of lights caused by a lens with an optic zone too small as a decentered lens or an excessively loose lens. |
front 41 Flat Cornea | back 41 A cornea with a K value less than 41.00 D. |
front 42 Fluid Lens | back 42 Power created by having a very convex or concave tear film. |
front 43 Fluorescein | back 43 An organic compound that is inert and used to stain the tear film for
contact lens fitting and to assess the integrity of the
cornea. |
front 44 Haptic | back 44 The part of a contact or intraocular lens that supports the optic portion and touches the peripheral or nonoptic portion of the cornea: the word indicates “fastening, contact, sense of touch.” |
front 45 Hydrogen Peroxide | back 45 A bactericide used for soft lenses. |
front 46 Keratoplasty | back 46 A corneal transplant. |
front 47 Lenticular Lens | back 47 Relatively large lens most suitable for large, flat eyes; consists of a central optic zone and a surrounding nonoptic flange. |
front 48 Limbal Zone | back 48 Junction between the periphery of the cornea with the sclera. |
front 49 Loose Lens | back 49 A contact lens with excessive movement; it can be caused by a lens that is too small in diameter, too thick or too flat. |
front 50 Meibomian Glands | back 50 Sebaceous glands of the eyelid. |
front 51 Microthin Lens | back 51 A lens less than 0.10 mm in thickness. |
front 52 Minus Carrier | back 52 A lens designed with an edge configuration similar to that of a minus lens that is thicker at its periphery; often used with high-plus lenses such as aphakic lenses. |
front 53 Monovision | back 53 Single-vision contact lenses used for presbyopes for whom the power of the lenses is such that one eye is used for distance vision and the other is used for near vision. |
front 54 Mydriatic Agent | back 54 A drug that causes the pupil to contract. |
front 55 Nomogram | back 55 A table of precalculated mathematical values used to arrive at the specifications of a rigid lens design. |
front 56 Orthokeratology | back 56 The technique of flattening the cornea and thus correcting refractive errors by the use of a series of progressively flatter contact lenses. |
front 57 Oxygen Flux | back 57 A measure of the amount of oxygen that will pass through a given area of material in a given unit of time. |
front 58 Oxygen Permeability | back 58 The degree to which a lens permits the passage of oxygen across it. It depends on the composition of the plastic (that is, silicone has excellent permeability, whereas PMMA has no permeability), the thickness of the lens, and its water content. It is often expressed as the DK value. |
front 59 Pachometer | back 59 An instrument used to measure the thickness of the cornea and depth of the anterior chamber. |
front 60 Photokeratoscope | back 60 An instrument designed to photograph annular rings of the cornea and to aid in making a contact lens that will contour to the cornea. |
front 61 Placido’s Disc | back 61 A disc with concentric rings to determine the regularity of the cornea when its reflection is revealed on the corneal surface. |
front 62 Plano Lens | back 62 A lens with zero power. |
front 63 Polymer | back 63 A chain of linked molecular unity of dimension greater than 5 monomer unity. |
front 64 Polymerization | back 64 The union of molecules of a compound to form larger molecules and a new compound. |
front 65 Polyvinyl Alcohol | back 65 A wetting agent. |
front 66 Prism Ballast Lens | back 66 Contact lens with base-down prism added inferiorly to improve the stability of as soft toric or rigid lens. Usually 1 to 1.5 D of prism is added. |
front 67 Radial Keratotomy | back 67 A surgical procedure in which clock like incisions are made into the cornea to flatten the cornea and correct myopic refractive errors. |
front 68 Residual Astigmatism | back 68 The astigmatism present after the corneal astigmatism has been nullified by a contact lens. |
front 69 Retroillumination | back 69 Light is focused on deeper structures such as the iris, while the microscope is adjusted to study the cornea. |
front 70 Schirmer Test | back 70 Measures normal tear secretion; the ability of the eye to wet in 5 minutes 15 mm of a 5 x 35 mm strip of filter paper. |
front 71 Semifinished Blank | back 71 A contact lens blank in which the posterior curve of the contact lens has been fabricated. |
front 72 Soaking Solution | back 72 A solution designed to keep a lens moist and free from contamination. |
front 73 Soper Lens | back 73 A rigid lens designed by Joseph Soper with a steep central posterior curve to accommodate large cones of keratoconus. |
front 74 Specular Reflection | back 74 A reflection from a mirror surface, such as the back of the cornea. |
front 75 Spheric Equivalent | back 75 It is the spheric power of the lens plus half the cylindric power. |
front 76 Sterilization | back 76 A method to ensure the complete death of all forms of bacteria fungi, and spores. |
front 77 Surfactant | back 77 A cleanser that acts on the surface of a contact lens. |
front 78 Tear Film Breakup Time (BUT) | back 78 An evaluation of tear quality; the tear film will normally break up in 10 to 30 seconds and show dry spots. Any dry spot that appears in less than 10 seconds is pathologic. |
front 79 Thermal Disinfection | back 79 Disinfection of a lens by heat. |
front 80 Thickness of a Lens | back 80 The measurement of the center of the lens. |
front 81 Thimerosol (Merthiolate) | back 81 A mercurial agent used for disinfection. Has a high ocular sensitivity rate. |
front 82 Three-Point Touch | back 82 That area of the cornea between the apical zone and the limbal zone. |
front 83 Truncation | back 83 A design feature used in toric lenses to reduce lens rotation by
cutting off a peripheral portion of the lens to conform with the lower
lid border. |
front 84 V-Groove Gauge | back 84 A ruler measure with a groove to measure the diameter of rigid lens. |
front 85 Visible Iris Diameter (VID) | back 85 A term that represents the iris diameter and aids in selecting the initial lens; often used in place of the corneal diameter. |
front 86 Warpage | back 86 A permanent bending of a rigid lens. May also refer to a semipermanent altering of the corneal curvature. |
front 87 Wet Storage | back 87 The use of soaking solution to store rigid contact lenses. |
front 88 Wetting Solution | back 88 Solutions that increase the spreading or wettability of liquids in the plastic contact lens by converting the surface of a lens from a hydrophobic to a hydrophilic surface. |
front 89 Chlorbutanol | back 89 An antimicrobial agent used in rigid lens disinfectants. |
front 90 Ascorbic Acid | back 90 One of the most common preservatives in soft contact lens disinfecting solutions. |