ASTIGMATISM

A defect in the eye whereby the light rays from an object are not brought to a single image point (condition where one part of the field is more out of focus than other parts. Clearness of vision can generally be restored by lenses.)

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AXIS

An imaginary straight line passing through a body or a system with respect to which this body or system is symmetrical

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BACTERIA

One-cell organism, some of which are disease producing

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BASE CURVE

When applied to a toric surface, the base curve is the weakest curve of the surface. When applied to lenses in general, the base curve is the curve common to a group of lenses.

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BEHAVIOR

The reaction of the individual to his environment (all types of muscular and glandular responses of the organism to stimulation)

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BELL RETINOSCOPY

A variation of dynamic retinoscopy in which the test object is moved toward the patient while the retinocsope is kept at a fixed distance

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BIFOCAL

Any lens containing two different powers for focusing at different distances

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BINOCULAR

Refers to the unification of the right and left fields of view

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BLIND SPOT

A certain portion of the retina where light rays focused will not be transmitted through the optic nerve; every individual has such a blind spot, but it may enlarge through disease or trauma (also called the optic disk)

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BLOCKING

Inhibition

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BLUR

Lack of clearness of the object of regard

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BLUR POINT

Under a given set of test conditions, the point at which the fixation target appears blurred on the introduction of gradually increasing prism and/or lens power

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BOOK RETINOSCOPY

Retinoscopy performed while the subject is reading

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BREAK POINT

The point at which diplopia occurs on gradually varying the prism or lens power during binocular fixation

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CANTHUS

The angle formed by the juncture of the eyelids

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CAPACITY

Potential or latent ability

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CASE ANALYSIS

A study of visual performance

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CATARACT

The condition of the eye whereby the crystalline lens loses transparency and obstructs the passage of light

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CENTERING

Selection of some area of space for attention and meaning (the computing process of “Where is it?”)

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CENTIMETER (cm.)

In the metric system, the hundredth part of a meter (.3937 inches)

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CENTRAL VISUAL FIELD

The area directly ahead in which the individual can see sharply and clearly, as opposed to peripheral field, or larger field, over which on can see indistinctl

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CHAINING

Process of arranging the significant examination findings above or below a horizontal line (used in analyzing cases)

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CHECKING

Marking the analytical findings which vary from the expected results of the tests

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CHEIROSCOPIC TRACKING

A vision therapy technique that involves hand-eye coordination in which a pattern is presented to one eye and the projected image is traced before the other eye

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CHOROID

The layer of cells between the retina and the sclera

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COMPREHENSION

The understanding of a written text through reading

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CONCAVE LENSES OR MINUS

A minifying lens that is designed to correct nearsightedness

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CONJUNCTIVA

The mucous membrane covering the anterior surface of thee eye (bulbar) and lining of the lids (palpebral)

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CONJUNCTIVITIS

The inflammation of the conjunctiva; also called “Pink eye”

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CONVERGENCE

Aiming of the eyes to see singly at a given distance

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CONVERGENCE INSUFFICIENCY

An inability to adequately converge (turn the eyes inward) or to sustain convergence for near visual tasks

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CONVEX LENSES OR PLUS

A magnifying lens that is used to correct farsightedness

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CORNEA

The transparent bulge of the front surface of the eye which represents the first part of the optical system and covers the iris and pupil

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CORNEAL ASTIGMATISM

Defect in the curvature of the cornea whereby light rays passing through the cornea produce aberrations and are not focused on the retina

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CORTICAL

Within the central nervous system

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CORTICAL LEVEL

Conscious level

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CRYSTALLINE LENS

A membrane lens which acts like the lens of a camera; the lens flexes to focus parallel light on the retina

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CYLINDER LENS

A lens that is designed to correct astigmatism. (Made in plus and minus with designated + or – preceding the power. It is always followed by an axis which is the direction in which there is no power of the cylinder.)

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DESCEMET’S MEMBRANE

The middle cell layer of the cornea

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DECENTRATION

The process by which the optical center of the lens is matched with the center of the patient’s pupil

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DEFECT

An impairment of performance forced on the organism from whatever cause

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DEVELOPMENT

The modification of growth by the activities and experiences through which the organism goes at various times

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DEVELOPMENTAL OPTOMETRY

A phase of functional optometry which holds that visual skills are learned performances which develop most effectively if under systematic professional guidance

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DIAGNOSIS

The procedure by which the nature of disease or disorder is determined by study of its origin, its evolution, and the signs and symptoms manifested by it

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DIOPTER

A unit of measurement to designate the refractive power of a lens or an optical system, the number of diopters of power being equal to the reciprocal of the focal length in meters; thus a 1 Diopt lens has a focal length of 1 m.

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DIPLOPIA

The condition in which a single object is perceived as two objects rather than as one; double vision

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DIRECT FIELD OF VISION

That portion of the field which is seen by the macula

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DISSOCIATION

Separating the binocular space lattice into two binocular ones

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DUCTIONS

Measured with bases-out and bases-in prisms to the point where the patient sees two images, then gradually reduced until the two images fuse (break and recovery)

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DYNAMIC RETINOSCOPY

Retinoscopy performed while the subject fixates a near object

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DYSLEXIA

A condition in which letters but not words may be read, or in which words may be read but not understood

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ECCENTRIC FIXATION

The person fixates the image of regard with an area other than the fovea

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EMMETROPE

An individual who has best visual acuity distance without minus lenses, and blur when plus lenses are applied

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EMMETROPIA

Theoretically normal eyesight

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ENDOTHELIUM

The cells which line the base layer of the cornea

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ENUCLEATION

The removal of the entire eye

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EPITHELIUM

The cells covering the outermost portion of the cornea

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ESOTROPIA

A condition where one eye, or both, turns inward

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EXOTROPIA

A condition where one eye, or both, turns outward

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FARPOINT

The point upon the visual axis of the eye which is sharply imaged on the retina when the accommodation is relaxed. The far point of a normal eye lies at infinity

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FARSIGHTED

Also called hyperopia, a condition where light rays focus behind the retina of the unaided eye

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FIELD STUDIES

Used to determine the area within which objects are more or less distinctly seen by the eye in a fixed position

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FIXATION

The process, condition or act of directing the eye toward the object of regard, causing, in a normal eye, the image of the object to be centered on the fovea

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FIXATION, ECCENTRIC

The person fixates the image of the object of regard with an area other than the fovea

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FOCAL POINT

The point of convergence or divergence of a pencil of light

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FOCUS

The point at which a pencil of rays or their prolongations can be made to meet after reflection or refraction

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FOVEA

The study of a tiny spot in the center of the macula through which vision is the sharpest (To see as clearly as possible, each eye must be turned so that the image of the object of regard falls directly upon it.) Color vision occurs here

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FUSION

Ability to perceive one object seen with the two eyes as a single object

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HETEROPHORIA

A muscular imbalance exists; however, the person can overcome it and still maintain approximately normal single binocular vision

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HOROPTOR

The sum total of points in space which can be seen singly by two eyes

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HYPEROPIA

The condition in which distant objects remain clear as plus lenses are added (same as farsighted)

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HYPERPHORIA

A tendency of one eye to turn above the other

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HYPERTROPIA

One eye is actually turned above the other

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INDIRECT FIELD OF VISION

The area outside the paramacular field

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INNATE

Patterns of behavior which are present at birth and are, therefore, present prior to experience

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IRIS

The colored membrane surrounding the pupil which acts like a camera shutter regulating the light entering the eye

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LACRIMAL GLANDS

The glandular system responsible for tearing

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LAG OF ACCOMMODATION

An amount that is subtracted from gross nearpoint accommodative tests

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LOCALIZATION

The placing of a source of stimulation with reference to the organism

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MACULA

The tiny area in back of the retina in which the nerve endings are more tightly packed than anywhere else in the retina, and through which normally the power to discriminate details is keen

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MATURATION

The process of growth whereby the state of complete development is attained

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METER

Basic unit of length in the metric system, equivalent to 39.37 inches

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MILLIMETER

One-thousandth of a meter (roughly 25 millimeters to one inch)

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MINUS

Term used to indicate the power of a concave surface or power of a lens whose concave surface is stronger than its convex surface

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MINUS LENS

(Concave) Changes path of light so that the focus is on the same side of the lens as is the object and closer to the lens than the object

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MONOCULAR

Pertaining to vision with one eye alone

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MOTILITY

The directed, integrated, rhythmic behavior of an organism

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MULTI VISION

Lenses designed with two or more foci

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MYOPIA

Condition wherein minus lenses are required to restore maximum distance visual acuity (same as nearsighted)

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NORMAL RETINAL CORRESPONDENCE (NRC)

The foveas and other corresponding areas of the two retinas are linked together so that when the images of an object fall upon them, fusion is achieved

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OCULAR DEFECTS

The end result of visual problems

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OCULOMOTOR DYSFUNCTION

Medical name for eye-tracking difficulties

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OD (oculus dexter)

Abbreviation meaning right eye

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O.D.

Doctor of Optometry

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OS (oculus sinister)

Abbreviation meaning left eye

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OU (oculi uterque)

Abbreviation meaning both eyes, together

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OPHTHALMIC

Pertaining to the eye

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OPHTHALMOLOGIST

A physician specializing in ophthalmology

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OPHTHALMOLOGY

The medical specialty that deals with diseases of the eye and eye surgery

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OPTIC NERVE

The part of the nervous system which transmits the impulses of sight from the retina to the brain

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OPTICAL CENTER

The direct center of an optical lens (Note: It is not the geometric center, but the point on the lens in which the light passes directly through without bending)

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OPTICIAN

One who assembles spectacles and dispenses them to patients

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OPTOMETRIST

One who has a professional degree as Doctor of Optometry (O.D.) and cares for vision through the prescription of vision therapy procedures, including lenses whenever appropriate

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ORGANISM

Any living thing, either animal or plant

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ORTHOPHORIA

The loss of potential ability to manipulate space beyond the plane of regard (The position of the eyes is not changed when the binocular space lattice is ruptured. It is a condition significant of the absorption of exophoria. It is a signal that a distortion exists in the visual pattern.)

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ORTHOPTICS

The evaluation and nonsurgical treatment of visual disorders caused by imbalance of the eye muscles

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PALPEBRAL FISSURE

The point where upper and lower eyelids meet

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PARAMACULAR FIELD OF VISION

The portion of the field which is immediately adjacent to and surrounds the macula

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P.D.

(Interpupillary Distance) The distance between the pupils of the two eyes

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P.D. RULE

A ruler having a scale both in millimeters and inches (used to measure the distance between the two eyes)

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PERCEPTION

Information received through the sense organs

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PERIPHERAL VISION FIELD

The area of vision lying just outside the line of direct sight

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PHORIA

Change in overt action in space (It informs as to how much accommodation may be changed with a lens, without causing an overt change in convergence. Phorias are measurements of the relationships existing to protect the integrity of convergence pattern.)

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PLANO

A lens with no refractive power; with neither plus or minus correction

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PLUS

The power of a convex surface or power of a lens whose convex surface is stronger than its concave surface

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PLUS LENS

(Convex) In an optometric prescription it produces an image more distant than the object

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PRESBYOPE

An individual who, because of age, cannot read standard type (20/20) at near with his basic finding (subjective) and to whom standard acuity can be restored by the use of plus lenses

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PRESBYOPIA

Due to age the crystalline lens of the eye loses elasticity and loses its power to accommodate for near objects so that they can be seen more clearly. (A bifocal with plus power can correct this problem)

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PRISM

An optical device which changes the direction but not the distance of the object (Used binocularly, bases-in prism changes condition as though the object were moved farther away; bases-out changes condition as though the object were moved closer.)

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PRISM DIOPTER

The unit of measurement of prism power (A prism whose power is one prism diopter produces a deviation of one centimeter at a distance of one meter.)

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PROGNOSIS

A prediction as to the probable outcome of a treatment program

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PUPIL

The black circular aperture under the cornea through which light enters the eye

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READING

The vicarious transfer of one person’s visual space world to another person through the use of the visual signs of language

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RECEPTOR

A sense organ, such as the eye

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RECOVERY

The return to single vision after doubling is produced by the use of prisms

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REFLEX

A local movement produced by stimulation of the part in question (a stereotyped contraction of an isolated group of muscles)

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REFRACTION

The ability of the eye to refract light entering it, so as to form an image on the retina (the measuring of the degree of refraction of an eye)

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RESIDUAL ASTIGMATISM

The amount of astigmatism present other than that produced by the corneal toricity

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RETARDED READER

A person with excellent acuity, high degree of binocular vision, but whose ability to interpret (to get meaning from the printed page) is below his/her age, grade, or intelligence level

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RETINA

The light sensitive membrane of the eye which receives the image formed by the optical system of the eye and is connected to the brain by the optic nerve

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RETINOSCOPY

The determination of the conjugate focus of the retina, hence the objective measurement of the refractive state of the eye, with a retinoscope

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ROTATIONS

The ability of the eye to follow a smoothly moving target in a circular pattern (It is one of the basic visual skills.)

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SACCADE

An abrupt voluntary shift in fixation from one point to another, as occurs in reading

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SCLERA

The dense fibrous opaque white outer coat enclosing the eyeball except the part covered by the cornea

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SCOTOMA

An isolated area of varying size and shape, within the visual field, in which vision is absent or reduced

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SEEING

The identification of reflected light; and an activity of the human body and mind (Its end result is human behavior in its fullest sense.)

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SINGLE BINOCULAR VISION

The attainment of single vision through the use of both eyes is the end result of fusion

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SKILL

A developed or acquired aptitude or ability; a motor performance that has become facile and well integrated; ease and precision in performance of motor acts; the ability to bring about some end result with maximum certainty and minimum outlay of energy

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SNELLEN CHART

A standard chart of block letters used to measure visual acuity

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SPACTIC MOVEMENTS

Tension type movements

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SPATIAL

Of or pertaining to space

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SPHERE

A lens with equal power in all meridians (whereas a cylinder has maximum power in one meridian and no power in the meridian 90 degrees away.)

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STANDARD PRACTICE

The “way it is done,” the customary procedure in performing a test

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STEREOPSIS

Depth perception; tridimensionality—the accurate location of objects in space

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STIMULI

Forces that act on the sense organs

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STRABISMUS

A muscle disorder producing an eye that turns inward or outward.

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STRESS

Any conditions impinging on the organism which require adjustive reactions

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SUBJECTIVE

The greatest amount of plus lens or the least amount of minus lens through which the patient obtains best acuity at 20 feet (#7 finding in the analytical examination)

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SUPPRESSION

A type of condition where areas of the total perceptual field have been eliminated by the organism

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SYMPTONS

The answers given by the modified organism to definite demands, a structural or functional change that indicates the presence of an anomalous condition

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SYNDROME

A characteristic sequence of symptoms grouped for case analysis

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TEMPLES

Parts of a frame, extending over ears, which hold the spectacles in place

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THERAPY

The treatment of disease or any physical or mental disorder by medical or physical means; the arranging of conditions that through repeated experience the individual may teach himself

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TRIFOCAL

A lens which has three different optical powers

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TROPIA

A turning of one or both of the eyes (strabismus, or squint)

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VERSIONS

The ability to fixate quickly and accurately with both eyes on a series of fixed objects—one after another—like figures on a scoreboard, or map, or blue print (This saccadic ability is also trainable.)

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VISAGRAPH III

An eye-movement recording system that measures the efficiency of silent reading

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VISION

The special sense by which objects, their form, color, position, etc., in the external environment are perceived, the exciting stimulus being light from the objects striking the retina of the eye; the act, function, process, or power of seeing; sight

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VISION THERAPY

Vision therapy is a sequence of neurosensory and neuromuscular activities individually prescribed and monitored by the doctor to develop, rehabilitate and enhance visual skills and processing. The vision therapy program is based on the results of a comprehensive eye examination or consultation, and takes into consideration the results of standardized tests, the needs of the patient, and the patient’s signs and symptoms. The use of lenses, prisms, filters, occluders, specialized instruments, and computer programs is an integral part of vision therapy. The length of the therapy program varies depending on the severity of the diagnosed conditions, typically ranging from several months to longer periods of time. Activities paralleling in-office techniques are typically taught to the patient to be practiced at home, thereby reinforcing the developing visual skills.

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VISUAL ACHIEVEMENT

The ability to interpret the external visual environment by means of the photo (light) receptor

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VISUAL ACUITY

The ability to discriminate contours; to tell when there is separation from background and whether there are one, two or three objects and not just a blur (It is the ability to perceive the interspace between two objects when it is very small. It is the reciprocal of the just resolvable visual angle measured in minutes)

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VISUAL AXIS

The main line of sight which extends from the fovea to the object of regard

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VISUAL BEHAVIOR PATTERN

It is made up of the behavior patterns of convergence and accommodation, the other skeletal postural patterns and the other contributory visceral patterns

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VISUAL GRASP

The ability to hold the eyes fixed on an object

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VISUAL PROBLEM

A visual pattern which has suffered a decrement in performance (It is a distorted response, a distortion in the manipulation of visual space.)

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VISUAL SPACE

The external world as perceived through the eyes

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VISUALIZATION

The skill of localizing and identifying objects from which there is no immediate visual input

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VISUALIZE

The ability to remember, know and predict where and what things were, are and will be in space-time

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VITREOUS

The transparent fluid which helps hold the shape of the inner eye

Additional terms and explanations can be found on the Children with Special Needs Website.

1 Portions are reprinted with permission from Lynn Fishmann Hellerstein, OD, FCOVD, and the Optometric Extension Program Foundation