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abo > Vocab > Flashcards

Vocab Flashcards

1
Q

Abberation

A

Deviation from a single focus of light rays emanating from one source

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2
Q

Accommodation

A

The ability of the eye to adjust focus for varying distances

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3
Q

Achromatic

A

Descriptive of a lens capable of refracting light without creating a rainbow effect

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4
Q

Acuity

A

Visual expression of sharpness of vision (20/20)

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5
Q

Addition

A

Difference in plus power between the reading and distance portions of a multifocal lens

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6
Q

Amblyopia

A

Loss of vision without any apparent disease of the eye

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7
Q

Ametropia

A

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

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8
Q

Anisekeikonia

A

A condition in which the image of an object as seen by one eye differs so much in size or shape from that seen by the other eye that the two images cannot be fused into a single impression

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9
Q

Anisometropia

A

A condition in which the refraction error of one eye significantly differs from that of the other

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10
Q

Anterior Chamber

A

Front cavity or compartment of the eye, located between the cornea and the crystalline lens. Contains the aqueous humor

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11
Q

Apex

A

Thinnest edge of a prism

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12
Q

Aphakia

A

An absence of the crystalline lens of the eye

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13
Q

Pseudophakia

A

Having a false lens

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14
Q

Aspheric

A

Not spherical; a lens surface having a number of curves with different radii

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15
Q

Axis

A

The meridian of no cylinder power in a spherocylinder lens

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16
Q

Base

A

Thickest edge of a prism

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17
Q

Base curve

A

The curve used as a base of a series of powers; the degree of curvature of the front surface of a lens

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18
Q

Beam

A

A group of parallel rays of light

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19
Q

Binocular

A

Pertaining to vision with both eyes

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20
Q

Caliper

A

Instrument used to measure thickness, calibrated in fifths and tenths of a millimeter

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21
Q

Canthus

A

The angle at either end of the slit between the eyelids

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22
Q

Cataract

A

A condition when the crystalline lens of the eye becomes opaque

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23
Q

Choroid

A

Vascular (blood-rich) layer of the eye; its function is to nourish the other parts of the eye, primarily the retina

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24
Q

Chromatic Abberation

A

Distortion of an optical image produced by the dispersion of light passing through a lens and generally characterized by blurred, multicolored edges

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25
Q

Ciliary body

A

The thick rim of choroid to which the crystalline lens is attached

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26
Q

Compound hyperopic astigmatism

A

The refractive error that results in two points of focus falling in front of the retina

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27
Q

Cones

A

Light sensitive cells in the retina responsible for color vision, daytime vision, and the central portion of the visual field

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28
Q

Conjunctiva

A

The clear membrane that lines the eyelids and covers the exposed surface of the eyeball

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29
Q

Conjunctivitis

A

Inflammation of the conjunctiva (“pink eye”)

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30
Q

Cornea

A

The refractive, transparent, anterior wall of the eye, equal to 43 diopters

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31
Q

The Five Layers of the Cornea

A

Epithelium
Bowman’s Membrane
Stroma
Descemet’s Membrane
Endothelium

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32
Q

Crown Glass

A

Pure silicate glass of general excellence for the spectacle lens; index of refraction is 1.523

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33
Q

Crystalline Lens

A

A transparent, colorless body suspended in the front part of the eyeball, between the aqueous humor and the vitreous humor. It’s function is to bring light rays to a focus on the retina

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34
Q

Cycloplegia

A

Paralysis of the ciliary body; drops used for diagnostic purposes

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35
Q

Decentration

A

Distance between the optical center placement of a lens and its geometric center; expressed in mmD

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36
Q

Diffusion

A

The scattering of light

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37
Q

Diopter

A

Unit of measurement of the refractive power of a lens. A lens whose focal length is one meter has a power of one diopter. The higher the dioptric power, the shorter the focal length

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38
Q

Diplopia

A

The seeing of one object as two, due to uneven tracking of the eyes (double vision)

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39
Q

Distortion

A

Defect in the lens which causes a straight line to appear curved

40
Q

Divergent

A

Two or more light rays proceeding outward from a point

41
Q

Emmetropia

A

The refractive condition of a normal eye. When the eye is at rest, the image of distant objects is brought to a focus on the retina

42
Q

Esophora

A

A tendency for one eye to deviate off the visual axis toward the other eye

43
Q

Esotropia

A

Actual deviation of one eye toward the vision axis of the other eye (cross eyed)

44
Q

Exophoria

A

A tendency for one eye to deviate off the visual axis away from the other eye

45
Q

Exotropia

A

Actual deviation of one eye away from the visual axis of the other eye (wall eyed)

46
Q

Far point

A

Point in space which is sharply focused on the retina with the eye’s accommodation relaxed

47
Q

Flint glass

A

A glass of high refractive index (1.65), containing lead

48
Q

Focus

A

The point to which the rays of a pencil of light converge or where they appear to diverge. In plus lenses, the focus is a real focus; in minus lenses, it’s a virtual focus

49
Q

Fusion

A

The power of coordination by which the images received by the two eyes become a single image

50
Q

Geometric center

A

Point where the diagonals of a boxed lens meet

51
Q

Glaucoma

A

An ocular disease having as its primary characteristic a sustained increase in intraocular pressure that the eye cannot withstand without damage to its structure or impairment of its function. Primary symptom is a loss of peripheral vision

52
Q

Hyperopia

A

Farsightedness; a refractive error in which, because the eyeball in short or the refractive power of the lens in weak, the point of focus rays of light from distant objects falls behind the retina. Correction to increase refractive power (a plus lens) is necessary for distance vision as well as near vision

53
Q

Index of refraction

A

The ratio of the speed of light in air to the speed of light in a given media

54
Q

Infinity

A

Distance great enough that the rays of light appear to be parallel; 20 ft or beyond

55
Q

Inset

A

Amount of decentration from the distance optical enter to the optical center of the bifocal segment, usually 1.5mm per eye

56
Q

Iris

A

The colored, circular membrane suspended behind the cornea and immediately in front of the lens. The iris regulated the amount of light entering the eye by changing the size of the pupil

57
Q

Irregular Astigmatism

A

A refractive condition caused by a cornea which is damaged and irregular. so that rays of light come to many focal points on the retina. Cannot be corrected by cylinders

58
Q

Iseikonic lenses

A

Spectacle lenses specially designed to manipulate image size when dissimilar sizes make it difficult to impossible for fusion to occur

59
Q

Lacrimal

A

Pertaining to tears; secretion or conduction of tears

60
Q

Limbus

A

The border between the iris and the sclera. Often used as a point of reference when manually measuring pupillary distance

61
Q

Macula

A

Oval area in the center of the retina devoid of blood vessels; most responsible for color vision and central vision

62
Q

Mechanical Center

A

Point on the lens surface around which a lens is edged

63
Q

Meniscus

A

Crescent-shaped lens with a curved, convex front surface and a curved, concave back surface (bent lens)

64
Q

Mixed Astigmatism

A

The refractive condition in which light comes to two points of focus where one point is in front of the retina, and the other is behind

65
Q

Monocular

A

Pertaining to vision in one eye; the distance from the center of the bridge of the nose to the center of the pupil of one eye

66
Q

Mydriasis

A

Prolonged or excessive dilation of the pupil of the eye, drops cause dilation

67
Q

Myopia

A

Nearsightedness; a refractive error in which the eyeball is too long in relation to its focusing power, thus the point of focus for rays of light from distant objects is in front of the retina. (a minus lens)

68
Q

Neutralization

A

The determination of dioptric power of an optical lens with a lens of the opposite power to cancel the original or return to plano; lensometry

69
Q

Nystagmus

A

Rapid, involuntary oscillation of the eyeballs, usually the result of brain or ear disease

70
Q

Oblique

A

Having a direction which makes an angle less or greater that a right angle with a surface of reference; neither parallel or perpendicuar

71
Q

Optic nerve

A

The special nerve of the sense of sight that carries impulses from the retina to the brain

72
Q

Optical Center

A

A point in a lens through which light passes with no deviation

73
Q

Orbit

A

The cavity in the skull that contains the eyeball

74
Q

Orthoptics

A

Technique of eye exercise designed to correct the visual axes of eyes not properly coordinated for binocular vision

75
Q

Phoria

A

Tendency for the eye to deviate from its visual axis or the normal

76
Q

Plano

A

no refractive power

77
Q

Presbyopia

A

Gradual lessening of the power of accommodation due to a physiologic change that becomes noticeable about the age of 35

78
Q

Prism

A

A device used to disperse light or change its direction; consisting of a transparent solid with two nonparallel plane faces

79
Q

Prism Diopter

A

A unit of measurement of the deviation of light by a prism

80
Q

Ptosis

A

Paralytic drooping of the upper lid

81
Q

Pupil

A

The central opening of the iris through which light is permitted to enter the eye

82
Q

Refraction

A

The determination of “refractive errors” of the eye. The change in direction as light passes obliquely from one medium to another of a different density

83
Q

Regular Astigmatism

A

A refractive condition in which rays of light come to two focal points, and can be corrected by cylinders

84
Q

Retina

A

The membrane which forms the inner lining of the back wall of the eye, constituted of two kinds of cells which respond to stimulus of light and send nervous impulses to the brain through the optic nerve

85
Q

Rods

A

Specialized visual cell in the retina responsible for peripheral and night vision

86
Q

Sclera

A

The “white” part of the eye; a tough covering which, with the cornea, forms the external, protective layer of the eye

87
Q

Simple hyperopic astigmatism

A

the refractive condition where one point of the focus falls on the retina and the other point of focus falls behind the retina

88
Q

Simple Myopic Astigmatism

A

The refractive condition where one point of the focus falls on the retina and the other point of focus falls in front of the retina

89
Q

Sphere

A

A lens with the same power and curvature in every direction

90
Q

Strabismus

A

Failure of the two eyes to simultaneously direct their gaze at the same object because of muscle imbalance

91
Q

Transposition

A

Changing the cylinder from a plus or minus to the opposite without changing its refractive power

92
Q

Tropia

A

An obvious deviation from normal of the axis of the eyes

93
Q

Vertex

A

The point at which the optical axis of a lens intersects the ocular surfaces

94
Q

Vertex Power

A

The refractive power of a lens measured from its vertex to its principal focus; significant in determining power of a corrective lens

95
Q

Vitreous humor

A

The transparent, colorless mass of soft, gelatinous material filling the eyeball behind the lens; keeps retina intact

96
Q

Zonule of Zinn

A

The suspensory apparatus of the lens; very thin, durable material that resembles fishing line

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