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CCOA > TERMINOLOGY > Flashcards

TERMINOLOGY Flashcards

1
Q

Abbe Number

A

A measure of lens light dispersion

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2
Q

Aberration

A

The failure of a refracting surface or lens to produce an exact point-to-point correspondence between an object or its image.

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3
Q

Accommodation

A

Adjustment by the eye for focusing clearly on near targets, which is accomplished by changing the shape of the crystalline lens through action of the ciliary muscle.

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4
Q

Add

A

the total dioptric power added to a distance prescription to supplement accommodation for reading

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5
Q

Against-the-rule Astigmatism

A

When the steepest meridian of the lens/prescription lies near the 0”-180” line

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6
Q

Age-Related Macular Degeneration (AMD/ARMD)

A

Age related deterioration of the macula

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7
Q

Albinism

A

A hereditary absence of pigment in the skin, hair, iris and retina; usually associated with the loss of visual acuity, nystagmus and photophobia; often accompanied by refractive errors

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8
Q

Amaurosis

A

Partial or total blindness

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9
Q

Amblyopia

A

Decreased visual acuity in one or both eyes, usually due to lack of sensory input during childhood. Often occurs without any apparent disease of the eye

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10
Q

Ametropia

A

An optical error of the eye in which the image of an object does not focus on the retina, when the visual system is at rest.

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11
Q

Amsler Grid

A

A diagram with horizontal and vertical lines used to detect macular distortion.

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12
Q

Anesthetic

A

A drug that induces an insensitivity to pain

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13
Q

Aniseikonia

A

The images of an object, which appear on each retina, are unequal in size or shape and cannot be fused into an image

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14
Q

Anisometropia

A

A difference in refractive error between the two eyes

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15
Q

Anterior Chamber`

A

The aqueous-filled space in the forward portion of the eye, bounded in front by the cornea and behind by the iris

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16
Q

Anterior Chamber Angle

A

The junction between the cornea and the iris where aqueous filters out of the eye

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17
Q

Anterior Segment

A

Referring to the front part of the eye (the lens forward)

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18
Q

Antihistamine

A

Drug used in the treatment of allergies

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19
Q

Antireflective Coating (ARC)

A

Reduces light reflections and increases the transmission of light through the lens

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20
Q

Aphakia

A

Absence of the crystalline lens of the eye

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21
Q

Applanation Tonometry

A

A method for determining intraocular pressure (IOP) by measuring force required to flatten an area of the cornea

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22
Q

Aqueous Humor (Aqueous)

A

Clear, watery fluid which fills the anterior chamber of the eye

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23
Q

Aspheric Lens

A

A non-spherical lens, in which the radii of the curvature increase towards the periphery rather than remaining equal at all points. Aspheric lenses reduce optical aberration and improve resolution

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24
Q

Asthenopia

A

Ocular fatigue caused by tiring of the muscle in and around the eye

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25
Q

Astigmatism

A

A refractive error in which light rays fail to come to a single focus on the retina because of differing amounts of refraction in the various meridians of the eye

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26
Q

Atroric Lens

A

Ophthalmic lens with aspheric curves on the back surface

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27
Q

Auto-refractor

A

A computerized machine that estimates the eye’s objective refractive power

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28
Q

Axial Length

A

Length of the eyeball

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29
Q

Bandage Contact Lens

A

Soft contact lenses used to protect the cornea

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30
Q

Base Curve

A

the curvature of the central portion of the posterior surface of the lens

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31
Q

Bicentric Grind

A

The grinding of the lower part of the spectacle lens to help compensate for a lens-induced vertical prism power that occurs with unequal power lenses

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32
Q

Bifocal

A

A lens with two optical zones, one for near vision and one for distance vision

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33
Q

Bilateral

A

Both eyes

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34
Q

Binocular vision

A

The ability to use both eyes simultaneously to focus on the same object and to fuse the images from both eyes into a single image

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35
Q

Biomicroscope

A

A corneal microscope for examination of the front portions of the eye, which provides a narrow beam of strong light

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36
Q

Blepharitis

A

Inflammation of the lid margins; AKA dandruff of the eyelids

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37
Q

Blepharoplasty

A

Any plastic surgery performed on the eyelids

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38
Q

Blind Spot

A

The natural sightless area of the visual field generated by the lack of photoreceptors where the optic nerve enters the eye

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39
Q

Blue Light

A

High energy visible light suspected to cause eye damage

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40
Q

Bowman’s Membrane

A

Layer of the cornea located between the epithelium and stroma

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41
Q

Braille

A

Tactile writing system used by individuals who are visually impaired

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42
Q

Bridge

A

the portion of the frame front that joins the two eye wires together. This part supports the frame on the patients nose

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43
Q

Canaliculi

A

Canal where tears pass from the puncta into the lacrimal sac

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44
Q

Canthus

A

The angle formed by the meeting of the upper and lower eyelids; specified as outer or temporal, and inner or nasal

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45
Q

Capsulotomy

A

A laser procedure used to remove capsular haze secondary to cataract surgery

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46
Q

Cataract

A

A clouding of the crystalline lens of the eye or its capsule, or both, with consequent loss of visual acuity

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47
Q

Cellulose Acetate

A

The most commonly used plastic frame material

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48
Q

Center Thickness

A

Thickness of the lens (measured in mm)

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49
Q

Central Retinal Artery Occlusion (CRAO)

A

Disease of the eye where retinal arterial blood flow is blocked. Symptoms include sudden painless, profound vision loss in one eye

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50
Q

Chalazion

A

Inflammatory enlargement of a meibomian gland in the eyelid

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51
Q

Chief Complaint

A

The main reason the patient has booked an appt

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52
Q

Chorioretinitis

A

Inflammation of the choroid and retina

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53
Q

Choroid

A

The vascular, intermediate layer of the eye, lying between the retina and sclera, which furnishes nourishment to the other parts of the eyeball

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54
Q

Choroiditis

A

Inflammation of the choroid

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55
Q

Ciliary Body

A

A portion of the vascular layer between the iris and the choroid, which consists of ciliary processes and ciliary muscle

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56
Q

Color Deficiency

A

Diminished ability to perceive differences in color- usually for red or green, rarely blue or yellow

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57
Q

Computer Vision Syndrome

A

Eye and vision related problems resulting from prolonged focus on a computer screen or digital device

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58
Q

Concave lens

A

A lens in which both surfaces curve inward, so it produces focal power by diverging parallel rays of light. It is also called a minus lens and is denoted by a minus sign

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59
Q

Congenital

A

Present at birth

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60
Q

Conjunctiva

A

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

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61
Q

Conjunctivitis

A

Inflammation of the conjunctiva

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62
Q

Contact Lenses

A

Lenses that are placed on the corneal surface or sclera. They have either and optical, therapeutic or cosmetic purpose

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63
Q

Contrast Sensitivity

A

A measurement which determines the observer’s ability to see a wide range of everyday objects under normal and reduced illumination conditions

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64
Q

Convergence

A

The process in which the visual axes of the two eye are directed toward the same near point, with the result that the eyes are turned inward

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65
Q

Convex lens

A

A lens in which both surfaces curve outward, so it produces focal power by converging parallel ray of light to a focal point. AKA plus lens and is denoted by +

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66
Q

Cornea

A

The transparent, dome-shaped tissue covering the iris and the pupil. The front “window” of the eye, diameter approx 12mm, responsible for approx 2/3 of refractive power of eye

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67
Q

Corneal Abrasion

A

An erosion of the superficial layer of the epithelium of the cornea (missing or injured cells) normally quite painful

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68
Q

Corneal Edema

A

Excessive accumulation of fluid in the cornea, due to disturbance in the mechanism of fluid exchange

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69
Q

Corneal Topography

A

A non-invasive imaging technique for mapping the corneal curvature in 3D

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70
Q

CR-39

A

A conventional plastic ophthalmic lens material

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71
Q

Crystalline Lens

A

The transparent lens which is suspended inside the eye immediately behind the iris. It is responsible for approx 1/3 of the refractive power of the eye

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72
Q

cup-to-disc ratio (C/D)

A

the relationship between the size of the optic cup and the optic disc of the optic nerve

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73
Q

Cycloplegic

A

A drug that temporarily paralyzes the ciliary muscle and dilates the pupil; often used to ascertain the refractive error

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74
Q

Cylindrical Lens

A

a toric lens, that is, one which has differing radii of curvature in different meridians, which causes the refractive power to vary in the different meridians; used to correct astigmatism

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75
Q

Dacryocystitis

A

Inflammation of the lacrimal sac

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76
Q

Daily Wear

A

Contact lenses worn during the waking hours

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77
Q

Dark Adaptaion

A

The ability of the eye to adjust to a dimly lit environment

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78
Q

Datum Line

A

The horizontal line that runs through the vertical center of a frame

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79
Q

Decentration

A

the displacement of the optical center of an eyeglass lens (not placing it in the geometric center of the frame) This is done purposefully to place the optical center in line with the visual axis of the eye or to induce prism

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80
Q

Depth Perception

A

The ability to perceive the relative position of objects in space

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81
Q

Dermatochalasis

A

Excess eyelid skin drooping over eye

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82
Q

Deutaronopia

A

A red-green colour deficiency resulting from an insensitivity to green light

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83
Q

Diastolic Pressure

A

The pressure in the arteries when the heart is at rest between beats. the bottom number in BP reading

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84
Q

Diopter

A

A unit of measurement of strength or refractive power of lenses; also can refer to the relative curvature of a lens surface

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85
Q

Diplopia

A

Double vision

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86
Q

Disposable Lens

A

Soft contact lens that is discarded after a specific time period

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87
Q

Distance Between Lenses (DBL)

A

The shortest distance between the nasal edges of 2 lenses

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88
Q

Distometer

A

instrument that measures vertex distance

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89
Q

Drusen

A

Yellowish deposits under the retina made up of lipids

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90
Q

Dyslexia

A

dysfunction in which the ability to read is diminished due to neurological or other non-optical problems

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91
Q

Ectropion

A

Turning out of eyelid

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92
Q

Effective Diameter (ED)

A

2x the distance from the geometric center of a lens to the furthest edge of a lens

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93
Q

Emmetropia

A

The focal condition of the normal eye in which there is no refractive error

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94
Q

Endophthalmitis

A

Inflammation of most of the internal tissues of the eyeball

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95
Q

Endothelium

A

innermost corneal layer which is a single layer of cells

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96
Q

Endpiece

A

The outer part of the frame front where the temples are attached

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97
Q

Entropion

A

Turning in of eyelid

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98
Q

Enucleation

A

complete surgical removal of the eyeball

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99
Q

Epiretinal Membrane

A

thin fibrous tissue that forms on the retina

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100
Q

Epithelium

A

outermost layer of the cornea

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101
Q

Esophoria

A

tendency of the eyes to turn too far inward under certain conditions

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102
Q

Esotropia

A

condition in which one or both eyes turn too far inward at all times AKA convergent strabismus CROSSED EYES

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103
Q

Exophoria

A

tendency of the eye to turn too far outward under certain conditions

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104
Q

Exophthalmos

A

abnormal protrusion of the eyeball

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105
Q

Exotropia

A

condition in which one or both eyes turn too far outward at all times AKA divergent strabismus

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106
Q

Extraocular/Extrinsic Muscles

A

6 muscles that are responsible for moving the eye; 4 recti and 2 oblique

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107
Q

Exudate

A

yellowish lesions (lipid proteins) found within the retina from leaking blood vessels caused by systemic diseases

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108
Q

Extended Wear

A

Contact lenses that can be worn during sleep

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109
Q

Eye Dominance

A

the tendency of one eye to assume the major function of seeing, being assisted by the less dominant eye

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110
Q

Eyewire

A

the portion of the frame that surrounds the lens

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111
Q

Face Form

A

the curve on the front of a frame AKA wrap

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112
Q

False Negative

A

failing to see a stimulus that was previously seen (ie px becomes tired during VF)

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113
Q

False Positive

A

Seeing a stimulus when one is not present (trigger happy during VF)

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114
Q

far-sightedness

A

hyperopia

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115
Q

Field of Vision (Visual Field)

A

the entire area which can be seen without shifting gaze

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116
Q

Fitting Cross

A

the location of a lens sitting right in front of a px pupil

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117
Q

Fitting Triangle

A

when a frame touches the head only on the nose and against the sides of the head round the ears

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118
Q

Fixate

A

the ability of an eye to move so an image is focused on the fovea

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119
Q

Floaters

A

Small particles consisting of cells or fibrin which move in the vitreous

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120
Q

Fluorescein Angiography

A

technique for examining the circulation of the retina and choroid using a fluorescein dye that is injected into the veins and viewed using a specialized camera

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121
Q

focus

A

point at which rays are converged after passing through a lens

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122
Q

fornix

A

pocket formed where the bulbar conjunctiva meets the palpebral conjunctiva

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123
Q

fovea

A

small depression in the central retina at the back of the eye; the part of the macula adapted for most acute vision

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124
Q

Frame PD

A

horizontal distance between the geometric centers of 2 lenses

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125
Q

Fresnel prism

A

a series of small prisms in a plastic sheet, which attach to eyeglass lenses to temporarily correct for eye misalignments

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126
Q

fundus

A

the back of the eye including the retina, optic nerve, macula and fovea

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127
Q

Fusion

A

the power of coordinating the images received by the 2 eyes into a single image

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128
Q

Gas Permeable Lenses

A

Contact lenses that allow oxygen and carbon dioxide to pass through them. this usually refers to a rigid lens, although soft lenses are also gas permeable

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129
Q

Geocenter

A

the intersection of the datum line and horizontal centers of each lens shape

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130
Q

Giant papillary conjunctivitis (GPC)

A

is a long-term hypersensitivity or allergic reaction resulting in bumps called papillae developing on the underside of the upper eyelid, usually accompanied by mucus discharge and itching

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131
Q

Glare

A

caused by a brightness greater than the eye can adjust to

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132
Q

Glaucoma

A

disease in which vision is lost due to damage of the optic nerve, it is often associated with increased pressure inside the eye

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133
Q

Gonioscope

A

a magnifying device which is placed on the cornea and in conjunction with strong illumination, is used to examine the angle of the interior chamber

134
Q

Grave’s Disease

A

autoimmune thyroid disease that causes protrusion of the eyes

135
Q

half-eye

A

frame designed to sit lower on the nose, to allow a patient to read and to look over the top to see distance

136
Q

hemianopsia

A

blindness of one half the field of vision of one or both eyes

137
Q

hepatitis B

A

infectious disease caused by a virus that affects the liver

138
Q

heterochromia

A

different coloured irises

139
Q

Human Immunodeficiency Virus (HIV)

A

disease caused by a virus that weakens the immune system and can lead to AIDS

140
Q

Hybrid Lens

A

a contact lens that has both soft and permeable materials

141
Q

Hyperopia

A

Farsightedness, hypermetropia. a refractive condition resulting from the tendency of rays of light to be out of focus on the retina when accommodation is relaxed. If the light rays could do so, they would reach their focal point behind the retina. mild=blurred vision near, higher=blurred vision at all distances

142
Q

Hyperphoria

A

tendency of one eye to deviate upward under certain conditions

143
Q

hypertension

144
Q

hypertropia

A

condition in which one eye deviates upward at all times

145
Q

hyphema

A

blood in the anterior chamber of eye

146
Q

hypophoria

A

tendency of one eye to deviate downward under certain conditions

147
Q

hypotropia

A

condition in which one eye deviates downward at all times

148
Q

injection

A

congestion of ciliary or conjunctival blood vessels; redness of the eye

149
Q

Inner Canthus

A

inner corner of the eye where the upper and lower lids meet

150
Q

Instrument Myopia

A

occurs when looking into an optical instrument and the person focuses on their eyes closer then needed to see the image

151
Q

Interpupillary Distance (PD)

A

pupillary distance, is the distance between the centers of the pupils of each eye (mm)

152
Q

Intraocular Lens (IOL)

A

artificial lens that is implanted in the eye during cataract surgery to replace the anatomical lens

153
Q

intraocular pressure (IOP)

A

fluid pressure or tension within the eye measured in millimeters of mercury (mmHg)

154
Q

Iris

A

coloured, circular muscle tissue behind the cornea and immediately in front of the crystalline lens. regulates the amount of light entering the eye by changing the size of the pupil

155
Q

Iritis

A

inflammation of the iris; pain, inflammation and discomfort from light, contraction of pupil, discolouration of iris

156
Q

Jaeger Test

A

test for near vision; lines of reading matter printed in a series of various sizes and typeface

157
Q

K-readings

A

corneal curvature measurements taken with a keratometer

158
Q

keratitis

A

inflammation of the cornea

159
Q

keratoconjunctivitis sicca

160
Q

keratoconus

A

progressive disease where the central corneal tissue protrudes forward dramatically making the cornea somewhat cone-shaped

161
Q

keratometry

A

measurement of the anterior curvatures of the cornea with a keratometer

162
Q

keratoplasty

A

the graft of a donor cornea to replace a damaged or diseased cornea

163
Q

Lacrimal Gland

A

gland with secretes tears

164
Q

lacrimation

A

production of tears

165
Q

Lacrimal sac

A

upper part of the nasal lacrimal duct; receives tears from the canaliculi

166
Q

LASIK

A

Laser-assisted in situ keratomileuses; laser eye surgery. corneal refractive surgery for the correction for myopia, hyperopia and astigmatism

167
Q

lateral

A

toward the ear, away from midline of the body

168
Q

Lateral Geniculate Body (LGB)

A

relay center that receives information from the retina and transmits it to the occipital lobe in the brain

169
Q

Lazy eye/amblyopia

A

decreased visual acuity in one or both eyes with no detectable cause

170
Q

Legal Blindness

A

visual acuity of 20/200 or less in the better eye after correction; or visual acuity of better than 20/200 but having a VF of no greater than 20’’ in better eye

171
Q

lens

A

refractive medium having one or both surfaces curved

172
Q

lens blank

A

a lens before it has been edged to fit into a frame

173
Q

lens calipers

A

instrument used to measure the center thickness of a lens

174
Q

lens clock

A

instrument for measuring the base curve of a lens

175
Q

Lens height (B)

A

vertical distance between the furthest top and bottom edges of a lens

176
Q

Lens Size (A)

A

horizontal distance between the furthest temporal and nasal edges of a lens

177
Q

Lensometer

A

manual or automated device used to determine the prescription of an ophthalmic lens

178
Q

leukocoria

A

white pupil

179
Q

light adaptation

A

the ability of the eye to adjust to an increased amount of light in the environment

180
Q

limbus

A

boundary between cornea and sclera

181
Q

low vision

A

binocular vision less than 20/60

182
Q

low vision aids

A

optical devices of various types useful to persons with vision impairment

183
Q

macula

A

the small area of the central retina that surrounds the fovea; this region provides the most distinct vision in the retina

184
Q

Major Reference Point (MPR)

A

the point on the lens where the prism is equal to that called for by the prescription. if an rx has no prism, the optical center and the MRP are located at the same place; in an Rx with prism, the OC and MRP are at different places

185
Q

Meibomian gland

A

gland located within the eyelids which secretes an oily layer of tear fluid

186
Q

medial

A

toward the nose or toward the midline of the body

187
Q

Minimal Blank Size (MBS)

A

the smallest lens blank that can be used to edge a given prescription

188
Q

Miotic

A

a drug that causes the pupil to contract

189
Q

monocular

A

refers to one eye only

190
Q

monovision

A

a type of contact lens fitting in which one eye is corrected for distance vison and the other is corrected for near vison

191
Q

mydriasis

A

pupil dilation.

192
Q

mydriatic

A

drug that dilates the pupil

193
Q

myodisc

A

ophthalmic lens used to correct very high myopic prescriptions

194
Q

multifocal lens

A

eyeglass lens that incorporates several different optical powers and allows the wearer to see clearly at multiple distances

195
Q

Multiple Sclerosis (MS)

A

Autoimmune central nervous system disease causing demyelination of nerves

196
Q

Myopia

A

nearsightedness; refractive error in which the eyeball is too long in relation to its focusing power, the focal point for rays of light from distant objects is in front of the retina. once the light rays reach the retina, they are out of focus

197
Q

nasal

A

towards the nose or toward the midline of the body

198
Q

Near Point of Accommodation

A

the nearest point at which the eye can perceive an object distinctly. it varies according to the power of accommodation

199
Q

Near Point of Convergence

A

the nearest single point at which the two eyes can direct their visual lines, normally about 3inches from the eyes

200
Q

nearsightedness

201
Q

neovascularization

A

formation of new blood vessels in a part of the eye, can occur in the cornea when it does not receive enough oxygen

202
Q

nevus

A

birthmark, freckle, mole

203
Q

night blindness

A

a condition in which vision diminishes greatly in faint light

204
Q

nystagmus

A

an involuntary, rapid movement of the eyeball; it may be lateral, vertical or rotary

205
Q

oblique astigmatism

A

when the strongest (steepest) and weakest (flattest) meridians of a lens are not at 90’ and 180’ but rather 45’ and 135’

206
Q

occluder

A

an opaque or translucent device that is placed before and eye to block vision

207
Q

Oculus Dexter (OD)

208
Q

Oculus Sinister (OS)

209
Q

Oculi Uniter (OU)

210
Q

ophthalmologist

A

medical doctor who specializes in diagnosis and treatments of defects and diseases of the eye, performing surgery whine necessary or prescribing other types of treatment; formerly called oculist

211
Q

ophthalmoscope

A

instrument used to examine the interior of the eye

212
Q

optic atrophy

A

degeneration of the nerve tissue, which carries messages from the retina to the brain

213
Q

optical center

A

the location in a lens where light will pass through without being bent

214
Q

optical cross (power cross)

A

represents an imaginary lens in which the power is labeled for both principal meridians, which are always 90’ apart

215
Q

optic chiasm

A

location where optic nerve fibres cross over in the brain

216
Q

optic disk

A

head of the optic nerve in the eyeball where the retinal nerve fibers leave the eye; responsible for the physiological blind spot

217
Q

optician

A

one who dispenses frames and lenses, based on a rx written by an Optometrist or Ophthalmologist; grinds lenses, fits them into frames, and adjusts the frame to the wearer

218
Q

optic nerve

A

nerve which carries visual messages from the retina to the brain

219
Q

optic neuritis

A

inflammation of the optic nerve

220
Q

optic tract

A

extension of the optic nerve within the brain located beyond the optic chiasm

221
Q

Optometrist

A

primary health care provider specializing in diagnosing and treating diseases and optical disorder of the eye, prescribing lenses, vision training, medicines and other treatments

222
Q

Optyl

A

plastic frame material that has a ‘memory’, it can be bent into any shape when heated and cooled. when heated again it will return to original shape

223
Q

orbital cellulitis

A

infection of the soft tissue of the orbit posterior to the orbital septum

224
Q

orthokeratology

A

practice of purposely flattening the cornea with a specially designed contact lens, used to reduce or eliminate myopia

225
Q

orthoptic training

A

series of scientifically planned exercises for developing or restoring the normal teamwork of the eyes

226
Q

outer canthus

A

outer corner of the eye where the upper and lower eyelids meet

227
Q

tachymetry

A

measuring the thickness of the cornea

228
Q

palpebral

A

pertaining to the eyelid

229
Q

palpebral fissure

A

space between the upper and lower eyelids

230
Q

retinal laser photocoagulation

A

heat from a laser used to destroy leaking blood vessels in the retina

231
Q

pantoscopic tilt

A

the angle of an eyeglass lens in relation to the vertical plane

232
Q

perimeter

A

instrument for measuring the field of vision

233
Q

Peripheral vision

A

ability to perceive the presence, motion or colour of objects outside the direct like of vision

234
Q

phacoemulsification

A

ultrasound technique used during cataract surgery to remove the natural lens in the eye

235
Q

phakic

A

refers to an eye that still possesses its natural lens

236
Q

phoria

A

latent deviation in which the eyes tend to turn from the normal position for binocular vision

237
Q

phoropter

A

instrument used for determining the refractive and binocular state of the eye

238
Q

photochromic

A

lens tints that lighten and darken according to the amount of UV the lens is exposed to

239
Q

Photophobia/photosensitivity

A

abnormal sensitivity to and discomfort from light

240
Q

photopsia

A

flashes of light

241
Q

photoreceptors

A

rods and cones

242
Q

pingeculae

A

yellow-white deposit on the conjunctiva

243
Q

plano

A

a lens with no rx

244
Q

plano-cylinder lens

A

lens where one principle meridian has no power. they are used for the correction of simple hyperopic astigmatism and simple myopic astigmatism

245
Q

polarization

A

type of ophthalmic lens coating that screens out horizontal reflections and reduces glare

246
Q

polycarbonate

A

high index plastic ophthalmic lens material that is impact resistant

247
Q

Posterior Capsular Opacification (PCO)

A

haziness of the lens capsule secondary to cataract surgery

248
Q

posterior chamber

A

narrow space between the back of the iris and the front surface of the crystalline lens, bounded by the ciliary body and filled with aqueous

249
Q

PRK

A

Photo refractive Keratectomy. type of laser eye surgery where the outer layer of the cornea is removed

250
Q

Prentice’s Rule

A

formula for calculating the prismatic effect induced at any point in a lens; prism diopters = decentration (cm) x lens power in diopters

251
Q

Presbyopia

A

condition common after age 40 in which gradual lessoning of the eye’s power of accommodation causes difficulty in seeing near objects

252
Q

Primary visual cortex

A

area within the brain responsible for processing visual information

253
Q

prism

A

triangular wedge shaped lens that bends but does not focus light rays toward the position of its base

254
Q

prism ballast

A

when a contact lens is thicker and heaver at the bottom so that it will remain oriented in a specific position

255
Q

progressive addition lens

A

PAL, a lens that gradually increases in + towards the bottom of the lens

256
Q

prosthesis

A

artificial substitute for a missing eye

257
Q

protanopia

A

re-green colour deficiency resulting from an insensitivity to red light

258
Q

pseudoisochromatic charts

A

charts with colour dots of various hues and shades indicating numbers, letters or patterns used for testing colour discrimination

259
Q

pseudophakia

A

eye whose natural lens has been replaced with an artificial one

260
Q

pseudotumor cerebri

A

neurological disorder characterized by increased pressure within the skull in the absence of a tumor or disease

261
Q

pterygium

A

triangular fold of growing membrane which invades the cornea; usually on medial side

262
Q

ptosis

A

paralytic drooping of the upper eyelid

263
Q

punctal plugs

A

tiny plugs that are inserted into the lacrimal puncta to block the drainage of tears, dry eye treatment

264
Q

puncta

A

small drainage holes located along the upper and lower lid margins

265
Q

pupil

A

circular opening in the centre of the iris which regulates the amount of light that enters eye

266
Q

pupillometer

A

device that measures the interpupillary distance (PD)

267
Q

Radial Keratotomy

A

refractive surgical procedure that was used to correct myopia in the past by making incisions into the cornea

268
Q

refraction

A

the bending of light rays as they travel from one medium to another

269
Q

refractive error

A

defect in visual system that prevents light rays from being brought to a single focus on the retina

270
Q

retina

A

thin membrane lining the back of the eye where optical images are received. converts images into electronic impulses and transmits them to the brain along the optic nerve

271
Q

retinal detachment

A

separation of the retina from the choroid

272
Q

retinitis

A

inflammation of the retina

273
Q

retinitis pigmentosa

A

a hereditary degeneration and atrophy of the retina, usually accompanied by misplaced pigment in the retina

274
Q

retinoblastoma

A

most common form of eye cancer affecting children

275
Q

retinopathy

A

disease of the retina, due to various causes

276
Q

retinopathy of prematurity

A

disease affecting pre-maturely born infants resulting in abnormal retinal blood vessels

277
Q

retinoscope

A

instrument for determining the refractive state of the eye by observing the movements of lights and shadows across the pupil by the light thrown onto the retina from a moving mirror

278
Q

retroscopic tilt

A

when bottom eye wires of a frame are further form the face than the top eye wires

279
Q

rods and cones

A

types of nerve cells that form layer of the retina and act as light receiving media CONES visual acuity and colour discrimination RODS motion and vision at night

280
Q

safety glasses

A

impact-resistant spectacles with or without correction for protection of eyes

281
Q

Schlemm’s canal

A

area where aqueous humour passes from anterior chamber into episcleral vessels

282
Q

sclera

A

white part of the eye- tough covering with the cornea forms the external protective coat of eye

283
Q

scleral contact lens

A

rigid contact lenses that vault over the cornea and are supported by the sclera

284
Q

scleritis

A

inflammation of teh sclera

285
Q

scotoma

A

blind or partially blind area in the visual field

286
Q

segment

A

seg, an area of a lens with power differing from that of the main portion

287
Q

segment height

A

height at which a bifocal/multifocal is placed in a lens based on the relationship of the patients facial structure to the shaper of a frame

288
Q

silicone hydrogel

A

soft contace lens material

289
Q

single vision lens

A

a lens having one focal length and spherical base curve

290
Q

sjogrens syndrome

A

inflammatory disease characterized by dry eyes and mouth

291
Q

slab-off

A

bicentric grind

292
Q

slit lamp

A

biomicroscope

293
Q

snellen chart

A

used for testing distance visual acuity, lines of letters, numbers or symbols in graded sizes drawn to Snellen measurements. Each size is labeled with the distance at which it can be read by the normal eye, most often used for testing vision at 20 feet

294
Q

soft lens

A

contact lens made of soft plastic that contains water and allows for oxygen transmission. soft lenses are characterized by comfort and ease of adaptation

295
Q

specific gravity

A

indicates the weight of a lens in grams per cm. the higher the number the heavier the lens material

296
Q

spherical equivalent

A

calculated using the sphere power plus half the cylindrical power

297
Q

spherical lens

A

a lens which refracts rays of light equally in all meridians

298
Q

spherocylinder lens

A

the two principal meridians are different in power, and neither one is plano. they are used to the correction of compound hyperopic astigmatism, compound myopic astigmatism and mixed astigmatism

299
Q

sphygmomanometer

A

instrument used to measure blood pressure

300
Q

stereoscopic vision/depth perception

A

ability to use both eyes together to perceive the retative position of objects in space

301
Q

strabismus/tropia/squint

A

a failure of the two eyse simultaneously to direct their gaze at the same object because of muscle imbalance

302
Q

string-mounted frame

A

frame that holds a lens in place with only a small reinforcing arm and a very fine nylon cord. also referred to as a nylon cord frame

303
Q

stroma

A

thickest corneal layer located between Bowman’s membrane and the Descemet’s membrane

304
Q

stye/hordeolum

A

acute inflammation of a sebaceous gland in the margin of the eyelid, due to and infection and usually resulting in the formation of pus

305
Q

surfactant

A

cleaning agents that are used to remove contact lens deposits

306
Q

systolic pressure

A

amount of pressure that blood exerts on a vessel while the heart is beating. top number in a blood pressure reading

307
Q

telescopic glasses

A

magnifying spectacles founded on the principles of a telescope; occasionally prescribed for improving very poor vision which connot be improved by ordinary glasses

308
Q

temple

A

attaches to the frame front and wraps around the patients ears

309
Q

temporal

A

toward the ear, away from midline of the body

310
Q

tonometer

A

instrument for measuring pressure inside the eye

311
Q

toric

A

lens with two different power curves at defined optical axes, used to correct astigmatism

312
Q

trabecular meshwork

A

area within the eye responsible for draining aqueous humor

313
Q

trabeculectomy

A

surgical removal of part of the trabecular meshwork used in the treatment of glaucoma to lower the IOP

314
Q

trabeculoplasty

A

laser treatment on the trabecular meshwork used in the treatment of glaucoma to assist the flow of aqueous humor

315
Q

transpose

A

convert a prescription of a sphero-cylindrical lens into the oppositely powered cylinder form (+ to - or vice versa)

316
Q

trichiasis

A

eyelashes grow inward

317
Q

trichromatic colour vision

A

normal colour vision derived from having three types of functioning cones

318
Q

trifocal

A

lenses that have 3 areas of viewing, each with its own power

319
Q

tritanopia

A

a rare from of colour blindness resulting from an insensitivity to blue light

320
Q

trivex

A

impact resistant ophthalmic lens material

321
Q

truncation

A

flattening of the lower edge of a contact lens, so that it will remain oriented in a specific position

322
Q

tunnel vision

A

contraction of the visual field to such an extent that only a small area of central visual acuity remains, thus giving the affected individual the impression of looking through a tunnel

323
Q

uveal tract

A

entire vascular layer of the eyeball including iris, ciliary body and choroid

324
Q

vasoconstriction

A

narrowing of blood vessels

325
Q

vertex distance

A

distance from the front surface of the eye to the back surface of the spectacle lens

326
Q

vision

A

the faculty of seeing, sight

327
Q

visual acuity

A

resolving power of the eye or the ability to see two separate objects as separate. ability of the eye to perceive the shape of objects in the direct line of vision, usually measure in terms of a Snellen fraction (20/20)

328
Q

vitrectomy

A

surgical removal of the vitreous

329
Q

vitreous humor (vitreous)

A

gelatinous transparent, colourless substance filling the space in the eyeball between the crystalline lens and the retina

330
Q

with-the-rule astigmatism

A

when the steepest meridian of a prescription/lens lies near 90 degrees

331
Q

zonules

A

radially arranged fibers that suspend the lens from the ciliary body and hold it in position

CCOA (1 decks)

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