Accomodation:  Focusing within the eye to increase the optical power to maintain a clear image as an object is moved closer.  This is accomplished by the natural lens of the eye changing its shape (both contracting to focus up close and then relaxing to focus on more distant objects).  A combination of ciliary musclecontraction and the zonular relaxation facilitates this change in shape.

Accomodative Spasm:  A muscle spasm of the natural lens of the eye in which the lens does not relax after accommodating.  This results in vision that is sharp for near but blurry for distance.  This condition can be helped with Mandel Vision computer tips. 

Amblyopia (A.K.A.:  “lazy eye”):  Decreased vision in one or both eyes when the eye(s) are otherwise physically normal.  This can be due to muscle alignment problems called strabismus or different prescriptions in the eyes, which is calledanisometropia.  This condition can usually be improved with patch therapy, but only if this is initiated prior to age 5.  The earlier the intervention, the better the prognosis will be.

Anisometropia:  Unequal refractive errors in the two eyes.  The difference is usually one diopter or greater.

Binocular:  Referring to or affecting both eyes.

Binocular Vision:  The blending of the separate images seen by each eye into one single image.  Insufficient functioning of this process can lead to diplopia (double vision).

Ciliary Body:  The tissue that lines the inside of the eye which is composed of theciliary muscle and other ciliary processes.  These ciliary processes produceaqueous.

Ciliary Muscle:  The smooth muscle portion of the ciliary body which is responsible for the contraction and relaxation of zonules which allow the lens of the eye to focus (accommodate) for near visual acuity.

Convergence:  Inward movement of both eyes toward each other.  This is crucial in maintaining single binocular vision during near vision tasks.

Convergence Insufficiency:  A weakening of the eye muscles responsible for pulling the eyes toward each other to maintain single vision during near vision fixation. This can cause eye fatigue as well as diplopia (double vision).

Depth Perception:    Awareness of the relative spatial location of objects; some being closer to the observer than others.  This can be binocular or monocular.

Diplopia (AKA:  double vision):  The perception of two images from one object.  These 2 images can be vertical, horizontal or diagonal from each other.  It occurs only with two eyes together and disappears when one eye is covered.

Dominant Eye:  The preferred eye for visual tasks.  This is also the eye that leads and controls the other eye during binocular eye movements.

Double Vision:  See:  Diplopia

Extraocular muscles  (EOM):  Six muscles around the eye that are responsible for the movement of the eyeball.

Eyestrain:  Discomfort or fatigue of the eyes usually after near vision tasks.

Inferior Oblique:  One of six extraocular muscles that move the eyeball.  The inferior oblique has three functions:  extorsion (rotating the top of the eye away from the nose; this increases as the eye turns outward), elevation (this increases as the eye turns inward) and it assists the lateral rectus in moving the eye outward (abduction).

Inferior Rectus:  One of six extraocular muscles that move the eyeball.  The inferior rectus has three different functions:  depression (moves the eye downward which increases as it turns outward); extorsion (rotates the eye outward especially on inward gaze) and it assists the medial rectus in moving the eye inward (adduction).

Lateral Rectus:  One of six extraocular muscles that move the eyeball.  The lateral rectus is responsible for moving the eye outward (abduction) from the straight ahead position.

Lazy Eye:  See:  Amblyopia

Medial Rectus:  One of six extraocular muscles that move the eyeball.  The medial rectus is responsible for moving the eye inward (adduction) from the straight ahead position.

Monocular:  Locating in or pertaining to one eye.

Ocular Motility:  The movement of the eyes which involves the extraocular musclesand their effect on eye movement.

Ophthalmic Technician:  An allied health professional (both certified and non-certified) who performs preliminary diagnostic testing for an ophthalmologist.

Ophthalmologist:  A surgeon (MD) who specializes in diagnosis and treatment of refractive, medical and surgical problems related to eye diseases and disorders.

Ophthalmology:  Medical specialty which deals with the eye, its function and diseases, including diagnosis and medical as well as surgical management of these diseases.

Optometrist:  Doctor of Optometry. (O.D.) specializing in vision problems, treating vision conditions with spectacles, contact lenses and vision therapy and may also prescribe medications for certain eye diseases.

Orthophoria:  Eyes that are aligned normally; the absence of an eye deviation (or eye turn).

Orthoptics:  The science that deals with the diagnosis and treatment of defective eye coordination, binocular vision, strabismus and functional ambylopia by non-medical and non-surgical methods.

Orthoptist:  A certified allied health professional in ophthalmology who analyzes and treats patients with dysfunctions of binocularity and/or ocular motility.

Patch Therapy:  Treatment of amblyopia which involves occluding an ambyopic patient’s better seeing eye to improve vision in the amblyopic eye.  This form of therapy is most effective when it is begun before age 8.

Steroscopsis:  See:  Binocular Vision

Strabismus (Deviation):  Eye misalignment or eyes that do not move normally, caused by extraocular muscle imbalance.  This imbalance causes the foveas, (the central point of the macula that produces the sharpest vision), of opposite eyes to be focused on different objects.  This can cause eyestrain as well as diplopia.

Superior Oblique:  One of six extraocular muscles that move the eyeball.  The superior oblique has three functions:  Intorsion (rotates the top of the eye toward the nose which increases as the eye turns outward); depression (which increases as the eye turns inward) and it assists the lateral rectus in moving the eye outward (abduction).

Superior Rectus:  One of six extraocular muscles that move the eyeball.  The superior rectus has three functions:  elevation (which increases as the eye moves outward); intorsion (rotates the top of the eye toward the nose, which increases as the eye turns inward) and it assists the medial rectus in moving the eye inward (adduction).

Zonules:  Radial fibers that suspend the crystalline lens of the eye from the ciliary body and hold it in position.  Zonules are one of two structures involved inaccommodation.