Terminology Of Contact Lenses

Front 1

Abrasion, Corneal

Back 1

Scraped area of corneal surface accomplished by loss of superficial tissue (epithelium)

Front 2

Accomodation

Back 2

The ability of the crystalline lens to adjust power to provide retinal focus of images of objects closer than optical infinity

Front 3

Add

Back 3

Additional amount of plus power required for focusing at near

Front 4

Amblyopia

Back 4

Loss of vision without any apparent disease of the eye

Front 5

Ametropia

Back 5

A refractive error in which the eye, when in a state of rest, does not focus the image of an object upon the retina; includes hyperopia, myopia, and astigmatism

Front 6

Aphakia

Back 6

Absence of the crystalline lens

Front 7

Apical, apex

Back 7

The extreme top or tip of a curve

Front 8

Apical bearing, apical touch

Back 8

The posterior lens curvature resting on the corneal apex

Front 9

Aqueous humor

Back 9

Clear, watery fluid that fills the space between the back corneal surface and the front vitreous surface, bathing the crystalline lens. Produced by ciliary processes, it nourishes the cornea, iris, and lens and maintains intraocular pressure

Front 10

Aqueous tears

Back 10

The watery component of the tears

Front 11

Arcuate stain

Back 11

An arc shaped corneal abrasion caused by the edge of a contact lens

Front 12

Aspheric

Back 12

Not spherical. A posterior or anterior lens surface design which flattens at a given rate (eccentricity) as the curve progresses toward the periphery

Front 13

Astigmatism

Back 13

A refractive defect where the refractive surface has different power in different meridians. As a result, the image formed of a point object will not be a point, but a line

Front 14

Axial edge lift

Back 14

Vertical distance from the lens edge to an extension of the base curve of a lens

Front 15

Axis, cylinder

Back 15

The weakest, or least curved, meridian on the surface of a cylindrical or torc surface

Front 16

Axis, principal

Back 16

An imaginary line going through the geometric center of an optical system, perpendicular to the surface

Front 17

Back toric

Back 17

A lens design with 2 principal curves at right angles to each other on the lens posterior

Front 18

Bandage lens

Back 18

Soft contact lens used for protecting damaged or irregular corneal surfaces

Front 19

Base curve

Back 19

Of a contact lens, the curvature of the posterior optical portion,otherwise known as the Central Posterior Curve (CPC)

Front 20

Bell's phenomenon

Back 20

Upward and outward deviation of the eyes occurring in sleep or with one closure of the eyelids

Front 21

Bicurve lens

Back 21

A lens consisting of 2 posterior curvatures; one central curve (base curve) and one peripheral curve

Front 22

Binocular

Back 22

Referring to or affecting both eyes

Front 23

Bitoric

Back 23

A lens design with 2 principal curves at right angles to each other on both the anterior and posterior lens surfaces

Front 24

Blends

Back 24

The junctures between posterior curves after being smoothed out by polishing

Front 25

Blepharitis

Back 25

Inflammation of the eyelids, usually with redness, swelling, and itching

Front 26

Blepharoplasty

Back 26

Any plastic surgery of the eyelids

Front 27

Bullous keratopathy

Back 27

Degenerative process characterized by small blister-like pockets that form in swollen corneal epithelial layers; markedly reduces vision

Front 28

Break-up time (BUT)

Back 28

Measurement of the time interval between a blink and the development of a dry spot in the pre-corneal tear film; less than 10 seconds is abnormal

Front 29

CAB (cellulose acetate butryate)

Back 29

A first generation, low Dk (4.0 Dk) gas permeable lens material

Front 30

Cataract

Back 30

A condition in which the crystalline lens of the eye, or its capsule, or both, become opaque with consequent loss of visual acuity

Front 31

Chalazion (internal hordeolum)

Back 31

Inflammatory enlargement of a meibomian gland of the eyelid

Front 32

Chord length

Back 32

The measurement of a straight line joining the ends of an arc

Front 33

CN bevel/anterior bevel

Back 33

Angulation placed on the anterior (front) surface of a lens to reduce edge thickness and decrease lid sensation

Front 34

Conjunctiva

Back 34

Mucous membrane that lines the eyelids and covers the front part of the eyeball

Front 35

Copolymer

Back 35

A polymer containing 2 or more different monomer units

Front 36

Cornea

Back 36

Clear, transparent portion of the outer coat of the eyeball; the "window" of the eye

Front 37

Corneal dystropohy

Back 37

Abnormal or defective development of the cornea; degeneration of the cornea

Front 38

Corneal graft (transplant)

Back 38

Operation to restore vision by replacing a section of opaque cornea with a clear section from a donor

Front 39

Cylinder

Back 39

An object whose surface is curved differently in different meridians with the axis having zero curvature

Front 40

Cylinder lens

Back 40

A lens with a different power in different meridians due to one or more surfaces having cylindrical or toric shape

Front 41

Cylinder power

Back 41

The algebraic difference in power between the principal meridians of a cylinder lens

Front 42

Daily wear lens

Back 42

A contact lens designed to be worn for less than 24 hours, with cleaning and disinfection performed between wearing periods

Front 43

Dellen

Back 43

Localized zone of corneal thinning, usually at the limbus, caused by excessive dehydration

Front 44

Dessication

Back 44

Drying of the cornea usually due to improper wetting of the horizontal corneal extremes

Front 45

Dimple veiling

Back 45

Indentations in the corneal epithelium caused by air bubbles getting between the back of the lens and the front of the cornea. Detected with fluorescein stain.

Front 46

Diopter

Back 46

A unit of measurement equal to the reciprocal meter, used to measure vergence of light and power of optical lenses

Front 47

Dk

Back 47

Refers to the inherent permeability of a lens material to allow the passage of gases through it. Dk/t- refers to the amount of oxygen (gases) which pass through a lens material of specified thickness

Front 48

Duo-chrome test

Back 48

Method of refining a refraction by comparing relative clarity of equal-size objects seen on red, then on green, background

Front 49

Edema, corneal

Back 49

Swelling of the cornea, which in turn causes a loss of clarity

Front 50

Eccentricity

Back 50

The rate or amount of flattening of an aspheric curve. Measured as "e" value

Front 51

Effectivity

Back 51

Changes in the vergence of light between one point and another. In contact lens practice this change is most often observed when the position of the correcting lens is moved from the spectacle plane to the corneal plane`

Front 52

EOP

Back 52

Equivalent oxygen percentage

Front 53

Erosion, recurrent corneal

Back 53

Episodic, periodic loss of corneal epithelium due to its failure to adhere properly to Bowman's layer. May follow minor scratch-type injury

Front 54

Extended wear lens

Back 54

A contact lens designed to be worn 24 hours per day, for up to 7 continous days

Front 55

Fenestration

Back 55

A tiny hole in a contact lens, made to enhance the transmission of tears and oxygen through the lens material

Front 56

Flare, aqueous

Back 56

Tyndall effect, or the scattering of light, in a beam directed into the anterior chamber. This scattering is a result of increased protein content of the aqueous humor, which is a sign of severe inflammation of the iris and/or ciliary body

Front 57

Flexible wear lens

Back 57

A contact lens designed for occasional overnight wear

Front 58

Fluorescein dye disappearance test

Back 58

Evaluates tear drainage system; dye dropped onto conjunctiva of an eye with normal drainage should disappear within 5 minutes

Front 59

Fluorescein pattern

Back 59

The appearance of the tear film distribution between the posterior of a rigid lens and the anterior corneal curvature as viewed with fluorescent dye

Front 60

Fluorescein, sodium

Back 60

Fluorescent dye that can be injected intravenously to study blood flow through the retina and choroid. It can also be applied directly in the palpebral fissure to detect corneal abrasions or wound leaks, or to evaluate the fit of rigid contact lenses

Front 61

Focal length

Back 61

The distance from the vertex of an optical surface to its focal point. The reciprocal of the focal length is the dioptric power

Front 62

Focal point

Back 62

The point along the principal axis of an optical system where incident parallel light will be focused after being converged or diverged by that system

Front 63

Fogging

Back 63

A refraction refinement technique where a plus powered lens is placed before the eye to relax accommodation

Front 64

Front toric

Back 64

A lens design with 2 principal curves at right angles to each other on the lens anterior

Front 65

FSA (fluoro-silicone acrylate)

Back 65

A rigid gas permeable material which contains fluorine for stability, wettability, and added oxygen transmission; silicone for oxygen permeability; and methylmethacrylate for machinability and good optical quality

Front 66

Giant papillary conjunctivitis (GPC)

Back 66

Allergic type of conjunctival inflammation associated with soiled soft contact lenses. Hard, flat papillae form a cobblestone pattern on undersurface of the upper eyelid

Front 67

GMMA (Glyceryl Methylmethacrylate)

Back 67

A non-HEMA soft lens material

Front 68

HEMA (Hydroxyethylethacrylate)

Back 68

Plastic polymer used to make soft lenses

Front 69

Herpes simplex virus (HSV)

Back 69

Virus that recurrently infected the cornea, producing branch-like ulcers (dendritic keratitis)

Front 70

Hydrogel

Back 70

A polymer that absorbs and binds water into its molecular structure

Front 71

Hydrophilic

Back 71

Water-loving

Front 72

Hyperflange

Back 72

A plus lenticular carrier

Front 73

Hypertonic saline

Back 73

Salt eater of a higher concentration (usually 5%) than normal saline (0.9%). Used in ointment for dehydrating a cornea swollen with water in diseases that damage the endothelial water pump system, such as Fuch's dystrophy

Front 74

Hypesthesia

Back 74

Impaired or decreased sensitivity to touch, as caused by damage to nerves supplying that region

Front 75

Hypoxia

Back 75

Deficiency of oxygen reaching tissues of the body

Front 76

Image

Back 76

An optical reproduction of an object by a lens or mirror. Real images are formed where converging light focuses, and virtual images are formed where diverging light focuses

Front 77

Index of refraction

Back 77

The ratio of the speed of light in a vacuum to the speed in another medium, indicating the medium's refractive ability

Front 78

Infinity, optical

Back 78

The distance light waves must travel from a source to lose all curvature, and be essentially parallel. This distance is considered to be 20 feet

Front 79

Injection (hyperemia)

Back 79

Increased blood flow; usually refers to eye redness caused by congestion of conjunctival blood vessels

Front 80

Intrapalpebral (fit)

Back 80

A well centered rigid lens that fits between the upper and lower eyelids, where the upper lid does not control the position of the lens

Front 81

Keratitis

Back 81

Corneal inflammation, characterized by loss of luster and transparency

Front 82

Keratoconus

Back 82

Degenerative cornea disease characterized by thinning and cone shaped protrusion of central cornea

Front 83

Keratometry (K readings, K's)

Back 83

Corneal curvature measurements obtained with a keratometer

Front 84

Lacrimal lens

Back 84

The lens that is formed by the tears that collect between the base curve of a contact and the anterior cornea

Front 85

Lensometer

Back 85

Instrument used for determining the refractive power of a spectacle or contact

Front 86

Lens

Back 86

Any piece of glass or other transparent material with ability to bend light rays in a predictable fashion

Front 87

Lenticular

Back 87

A lens design using a non-optical portion (carrier) in the periphery of the lens to form edges of a desired thickness

Front 88

Lid attachment (fit)

Back 88

A rigid lens which is tucked under the upper eyelid for better centration and comfort. The eyelid keeps the lens in position between blinks

Front 89

Lift off/stand off

Back 89

Pertains to a lens which is fit excessively flat, causing the edge to lift away or stand off from the cornea

Front 90

Light

Back 90

That portion of the electromagnetic spectrum that gives rise to the sensation of sight through stimulation of the retina

Front 91

Limbus, corneal

Back 91

Transitional zone where the cornea joins the sclera and the bulbar conjunctiva attaches to the eyeball. About 1-2 mm wide

Front 92

Macula lutea

Back 92

"Yellow spot." Small specialized central area of the retina, surrounding the fovea; responsible for acute central vision

Front 93

Meibomitis

Back 93

Inflammation of the meibomian glands

Front 94

Microcystic edema

Back 94

Advanced form of edema involving the deeper cell layers of the epithelium

Front 95

Microcyst

Back 95

A tiny cyst, frequently of such dimensions that a magnifying lens or microscope is required for viewing. Corneal microcysts can be caused by hypoxia

Front 96

Minus lens

Back 96

A lens that is thicker at the edges than at center, which increases divergence of incoming light rays. Used in correcting myopia (nearsightedness)

Front 97

Mires

Back 97

Focusing guides on an optical instrument that aid in measurement, such as the circular targets in the keratometer

Front 98

Monocular

Back 98

Referring to or affecting one eye

Front 99

Nanometer

Back 99

Unit of wavelength of light; one billionth of a meter

Front 100

Nearvision

Back 100

Visual acuity measured at approximately 14in, correspondent to normal reading distance

Front 101

Neovascularization

Back 101

Abnormal formation of new blood vessels

Front 102

Normal

Back 102

In optics, a line drawn perpendicular to the surface

Front 103

Object

Back 103

The source of light being imaged by an optical system

Front 104

Objective examination

Back 104

Examination not requiring answers or observations from the patient

Front 105

Ophthalmologist

Back 105

Physician specializing in medical and surgical treatment of eye disorders

Front 106

Ophthalmoscope

Back 106

Instrument used for examining interior of the eye, especially the fundus

Front 107

Optician

Back 107

Specialist who makes and adjusts optical aids from prescriptions supplied from an ophthalmologist or optometrist

Front 108

Optics

Back 108

Branch of physics involved in light, including its refraction and reflection by lenses, prisms, mirrors and the eye

Front 109

Optometrist

Back 109

Eye care specialist licensed to prescribe eyeglasses and contacts, examine eyes and detect eye diseases

Front 110

Over-refraction

Back 110

Method of testing appropriateness of optical correction, by adding or subtracting power, utilizing trial lenses, placed in front of a lens already on the eye

Front 111

Overwear syndrome (OWS)

Back 111

Pain, sensitivity to light, corneal swelling, and epithelial erosion, following prolonged wear of contacts

Front 112

Pachymetry

Back 112

Test for measuring corneal thickness

Front 113

Pathology

Back 113

The medical science that deals with all aspects of disease, but with special preference to the essential nature, the causes, and development of abnormal conditions, as well as the structural and functional changes that result from the disease processes

Front 114

Permeability

Back 114

The ability of a lens material to allow the passage of gases

Front 115

Phoropter

Back 115

Refractive device combining a large variety of spherical and cylindrical lenses, prisms, and occluders, used to determine the eye's optical correction

Front 116

Photophobia

Back 116

Abnormal sensitivity to and discomfort from light

Front 117

Pleomorphism

Back 117

Occurrence in more than one form; the existence of more than one morphological type in the same species

Front 118

Plus lens

Back 118

A lens that is thicker at center than at edges, which increases convergence of incoming light rays. Used in correcting hyperopia (farsightedness)

Front 119

PMMA (Polymethylmethacrylate)

Back 119

Plastic polymer used to make hard contacts (impermeable to gases)

Front 120

Polymegathism

Back 120

A variation in cell size

Front 121

Polymer

Back 121

Small chemical units, or monomer, linked together to form a repeating chemical chain of high molecular weight

Front 122

Pooling

Back 122

Accumulation of tears under a lens, visible when viewed with fluorescein dye, indicating an area of clearance between the lens and the cornea

Front 123

Power

Back 123

Lens focusing ability in diopters

Front 124

Presbyopia

Back 124

Diminished focusing ability of the eye for near vision, associated with loss of elasticity of the crystalline lens from aging

Front 125

Principal meridians

Back 125

The meridians of most and least curvature, or greatest and least power, on a cylindrical or toric surface

Front 126

Prism

Back 126

An optical device with non-parallel sides.

Front 127

Prism ballast

Back 127

A prismatic shape used in contacts to stabilize the lens by preventing rotation

Front 128

Prism diopter

Back 128

The unit of measurement to describe the power of a prism to deviate light. One prism diopter produces a deviation of one cm at a distance of one mter

Front 129

Pterygium

Back 129

A triangular fold of growing membrane that may extend over the cornea from the sclera. It occurs most frequently in a person exposed to dust or wind. or excessive UV

Front 130

Punctate keratitis

Back 130

Corneal inflammation characterized by small superficial corneal lesions. Symptoms include foreign body sensation and photophobia

Front 131

Radiuscope

Back 131

Instrument used for measuring back surface curvature of a contact

Front 132

Radius of curvature

Back 132

An expression of the curvature of a surface by stating the length of the curve's radius. The shorter the radius, the steeper the curve. Base curves of contacts are usually expressed in radius of curvature

Front 133

Ray

Back 133

A line depicting the direction of a light wave

Front 134

Reflection

Back 134

Bouncing back of light rays by a surface

Front 135

Shore hardness

Back 135

Non-penetrating measurement of rigid contact lens material surface hardness or rigidity

Front 136

Single-cut lens

Back 136

A lens with no lenticular carrier

Front 137

Slit lamp (Biomicroscope)

Back 137

Binocular microscope used for measuring the eye. Consists of a microscope and q light source. Allows examination of cornea, Lens, and otherwise clear fluids and membranes in layer by layer detail

Front 138

Snellen chart

Back 138

A test of visual acuity. The chart has rows of letters, numbers, or symbols in standardized graded sizes

Front 139

SOAP

Back 139

Abbreviation for subjective, objective, assessment, and plan which describes a technique for conducting an examination of a patient

Front 140

Spectacle blur

Back 140

Blurred vision through spectacles after removal of contact lenses

Front 141

Spherical

Back 141

Having the same radius of curvature in all Meridians

Front 142

Spherical equivalent

Back 142

Substitution of a spherical power for a cylindrical one, using the power halfway between those located at the principal meridians

Front 143

Staining

Back 143

The process of putting dye in the eye. Also used when epithelial damage is detected with the aid of fluorescein

Front 144

Striae

Back 144

Wrinkles or folds seen in the choroid or cornea

Front 145

Refraction

Back 145

The change in direction of light as it passes into a transparent medium of different index

Front 146

Subjective examination

Back 146

An exam that requires input from the patient

Front 147

Refractive error

Back 147

Optical defect in an unaccommodated eye where parallel will light rays do not focus sharply on the retina

Front 148

RGP

Back 148

Rigid gas permeable

Front 149

Residual astigmatism

Back 149

Astigmatism left uncorrected

Front 150

Retinoscope

Back 150

An instrument for objectively determining the refractive state of the eye

Front 151

Rockwell hardness

Back 151

Hardness measurement standard where lens surface hardness is measured by pressure and penetration

Front 152

SA (Silicone Acrylate)

Back 152

RGP material which combines silicone for oxygen transmissibility and methacrylate for optical quality, lens machinability, and stability

Front 153

Schirmer tear test

Back 153

A test performed using filter paper strips to measure tear quantity

Front 154

SCL

Back 154

Soft contact lens

Front 155

Tear meniscus

Back 155

Pool of tears located under the periphery of a rigid contact which indicates the amount of lift or clearance; also, tears that collect along the lid margins

Front 156

Tear pump

Back 156

Created by a lens design which provides an adequate tear meniscus at the lens periphery and a base curve/cornea relationship, to allow the exchange of tears between the back of the lens and the front of the Cornea. this provides adequate oxygenation and debris removal each time the contact lens wearer blinks

Front 157

Tetracurve lens

Back 157

A lens design with four posterior curves; a central posterior curve and three Peripheral curves

Front 158

Thick lens

Back 158

Any lens exhibiting a change in vergence between the front and back surfaces that is too great to be ignored. Such a lens will have different front and back vertex powers, and therefore different front and back focal lengths

Front 159

Three-and-nine o'clock staining (3&9 staining)

Back 159

Horizontal areas of the cornea which characteristically dry out and become damaged

Front 160

Toric

Back 160

The shape of a surface that is curved differently in different meridians, but differing from a cylinder in that no meridian is perfectly flat

Front 161

Toric lens

Back 161

Lens with a cylindrical component, used to correct an astigmatic error

Front 162

Tricurve lens

Back 162

A lens designed with 3 posterior curves; a central posterior curve and 2 peripheral curves

Front 163

Truncation

Back 163

A rotational control achieved by making the bottom edge of the lens flat

Front 164

Vault

Back 164

Area of clearance between the posterior curvature of a lens and the anterior curvature of the cornea

Front 165

Vergence

Back 165

The power of a light wave at a particular distance from its source or focus, expressed in diopters. Light can exhibit convergence or divergence

Front 166

Vernal conjunctivitis (vernal catarrh)

Back 166

Allergic conjunctival inflammations with itching and excess mucous, recurring in children in warm months. Numerous small lumps (papillae) form on the palpebral conjunctiva

Front 167

Vertex

Back 167

The point at which the principal axis intersects an optical surface

Front 168

Vertex distance

Back 168

The distance between the back vertex of the correcting lens, and the front surface of the eye

Front 169

Vertex power

Back 169

The reciprocal of the focal length an optical surface, lens, or system. Front vertex power is the reciprocal of the front focal length, as measured from the front vertex. Back vertex power is the reciprocal of the back focal length

Front 170

Wetting angle/contact angle

Back 170

Antiquated measurement of the spreadability of water over a lens surface. Used to predict RGP lens material wettability and comfort on the eye

Front 171

Wound leak

Back 171

Escape of fluid or tissue through a cur or wound. May be a complication of ocular surgery, requiring repair

Front 172

K

Back 172

refers to the flattest of the primary meridians as measured by keratometry

Front 173

Sagittal Depth

Back 173

the distance between the posterior surface of the central area of the lens and the flat surface

Front 174

Dispersion

Back 174

The separation fo white light into its spectral colors

Front 175

Diuretic

Back 175

Substance that increases the amount of urine excreted

Front 176

Focus

Back 176

The point along the principal axis of an optical surface that light converges to, or diverges away from, after encountering that surface

Front 177

Macula

Back 177

The most sensitive part of the retina. Would be located where the principal axis intersects the retina

Front 178

Pencil

Back 178

A small cluster of light rays

Front 179

Reduced Distance

Back 179

When light travels through substances other tan air, the "equivalent air distance" or "reduced distance" can be found by dividing the real distance by the index of the substance

Front 180

Thin lens

Back 180

Any lens exhibiting a negligible change in vergence between the front and back surfaces. Such a lens will have equal front and back vertex powers, and unequal front and back focal lengths

Front 181

Anterior Optical Zone (AOZ)

Back 181

Diameter of the anterior power curve

Front 182

Arbor

Back 182

Brass tool that holds a lens blank for polishing or surface cutting

Front 183

Back Vertex Power

Back 183

Power of the lens when oriented so that light enters the anterior surface and exits the posterior surface. Measured with the back surface against the lens stop of a lensmeter

Front 184

Collet

Back 184

A tool that works like a vise to hold a lens blank for cutting on a lathe

Front 185

Diameter

Back 185

Overall diameter (OAD), total diameter. The chord length of a lens, measured across the back surface from edge to edge

Front 186

Edge Lift

Back 186

Distance between the lens edge and the corneal surface

Front 187

Front Vertex Power

Back 187

Power of the lens when oriented so that light enters the posterior surface and exits the anterior surface. Measured with the front surface against the lens stop of a lensmeter.

Front 188

Homopolymer

Back 188

A polymer in which all monomer units are the same

Front 189

Intermediate Peripheral Curve (IPC)

Back 189

A posterior curve that is flatter than the secondary curve, but steeper than the posterior peripheral curve (PPC)

Front 190

Lens Blank (Button)

Back 190

A solid piece of CL material cut from a long cylindrical rod, resulting in round shape with 2 flat faces. Convex and concave surfaces are cut at these faces to from a CL. A button measures 13mm in diameter and 5mm in thickness

Front 191

Myoflange

Back 191

A minus lenticular carrier

Front 192

Peripheral Curve

Back 192

Any curve that is applied outside of the optical zones of the lens posterior or anterior surfaces

Front 193

Posterior Peripheral Curve (PPC)

Back 193

The outermost, flattest curve applied to the lens posterior

Front 194

Posterior Optical Zone (POZ)

Back 194

The central portion of the lens posterior through which the patient see; the diameter of the base curve

Front 195

Power Curve

Back 195

The central anterior curve of a CL

Front 196

Secondary Curve (SC or SPC)

Back 196

The posterior peripheral curve that is applied just outside of the central posterior curve (CPC)

Front 197

Swarf

Back 197

The string of plastic formed as the diamond cutter moves across the lens blank during surfacing