ACCOMMODATION:
The focusing of the eye for seeing at different distances.This is accomplished by changing the shape of the crystalline lens, thus focusing an image on the back of the eye.

AMBLYOPIA:
Uncorrectable vision as a result of disuse. Glasses or contact lenses will not improve vision with this condition. Also know as lazy eye.

ANOPHTHALMOS:
Without an eyeball.

APHAKIA:
Without a crystalline lens.(as in after cataract surgery)

ASTIGMATISM:
Refractive error in which light rays focus at different places inside the eye.

BLEPHARITIS:
Inflammation of the eyelids and lid margin.

BLEPHAROSPASM:
Involuntary twitching of the eyelids.

BLINDNESS:
By definition, in the US, blindness is corrected visual acuity of 20/200 or less in the better eye, or a visual field of 20 degrees or less in the better eye.

CATARACT:
An opacity in the crystalline lens.

CHALAZION:
Inflammation (granulomatous) of a meibomian gland characterized by a large focal area of eyelid swelling.

CHEMOSIS:
Conjunctival swelling.

CILIARY BODY:
It is a structure which consists of the ciliary processes and ciliary muscles. The ciliary body produces aqueous, which provides nutrients to the eye and maintains ocular pressure. The ciliary muscles provide the focusing ability of the eye.

CONES AND RODS:
Both are retinal photoreceptor cells. Cones provide sharp visual acuity and color vision, while rods aid with night vision and peripheral vision.

CONJUNCTIVA:
Mucous membrane lining the inside portion of the eyelids and the anterior sclera.

CORNEA:
Transparent portion of the outer eye which functions in focusing light.

CRYSTALLINE LENS:
Transparent lens inside the eye which functions to focus light on the retina.

DIPLOPIA:
Viewing a single image as two.

ECTROPION:
Turning out of the eyelid.

EMMETROPIA:
No refractive correction required.

ENTROPION:
Turning in of the eyelid.

ENUCLEATION:
Surgical removal of an eye.

EPIPHORIA:
Tearing.

ESOPHORIA:
The tendency of the eyes to turn in.

ESOTROPIA:
Actual inward deviation of an eye.

EXOPHORIA:
The tendency of the eyes to turn out.

EXOTROPIA:
Actual outward deviation of an eye.

FOVEA:
Portion of the retina that provides the best visual acuity. The area of central vision.

GLAUCOMA:
Increased intraocular pressure causing damage to the optic nerve.

HYPEROPIA:
A refractive error in which the image focuses behind the retina. Typically, vision is good at a distance, but difficulty with near tasks may occur.

KERATOCONUS:
Cone-shaped deformity of the cornea.

MYOPIA:
Also known as nearsightedness, myopia is a refractive error in which the image focuses in front of the retina. Typically, near vision is good, but difficulty may occur with viewing distant images.

OPTIC NERVE:
The nerve that trasmits neural signals from the retina to the brain.

PHOTOPHOBIA:
Sensitivity to light.

PRESBYOPIA:
Age related blurred near vision--onset approximately age 40.

PTERGIUM:
Growth on the conjuctiva that may encroach on the cornea.

PTOSIS:
Drooping eyelid.

RETINA:
The innermost structure of the eye made up of rods and cones. The retina turns the light image into a neural signal.

RETINAL DETACHMENT:
Separation of the retina from its attachment to the back of the eye.

SCLERA:
The tough white part of the eye that gives the eye its shape.

STRABISMUS:
Manifest deviation of the eyes.

STY:
External inflamation of lid margin characterized by swelling and inflamation caused by oil gland blockage.