Glossary of Terms


Accommodation focusing the eye to achieve clear vision at a specific distance.

Amblyopia – also known as “lazy eye,” is loss of lack of development of clear vision in just one eye. The cause is the lack of use of that eye in early childhood.

Anisocoria is when the pupils are not the same size. One pupil may be bigger than normal (dilated), or one pupil may be smaller than normal (constricted), resulting in different sized pupils.


Astigmatism is a vision condition that causes blurred vision due either to the irregular shape of the cornea, the clear front cover of the eye, or sometimes the curvature of the lens inside the eye.

Binocularity the ability of the eyes to work together as a team, seeing with two eyes simultaneously. Poor eye coordination comes from lack of adequate vision development or improperly developed eye muscles.

Blepharitis Inflammation of the lid margins; also known as dandruff of the eyelids.

Cataracts is the term used when the natural lens of your eye becomes cloudy, causing blurred and distorted vision.

Color Deficiency is the inability to distinguish certain shades of colors or, in more severe cases, see colors at all. Color deficiencies are almost always hereditary and affect one in twelve boys, but only one in two hundred.

Conjunctivitis Inflammation of the conjunctiva; often referred to as “pink eye.” 

Conjunctivochalasis mimics dry eye and is a loosening of the tissue surrounding the eyeball.


Convergence Insufficiency is an eye coordination problem in which the eyes have a tendency to drift outward when reading or doing close work.

Emmetropia is a refractive condition of the eye that does not require correction. An emmetropic eye can focus images clearly when completely relaxed.

Glaucoma is the eye disease that causes your eye to have excessively high pressure, which can lead to long-term damage of the nerve in the eye.

Hyperopia is often called farsightedness. This vision condition occurs when distant objects are usually seen clearly, but close objects do not come into proper focus.

Index  of Refraction in eyeglass material indicates how fast light travels through the material. The higher the index the thinner the material. For example CR-39 plastic is 1.498 and a high index material may have a refractive index of 1.74.

Keratoconus is an eye disease that is characterized by thinning and steepening of the corneaKeratoconus results in visual distortion often not correctable by traditional glasses.

Macular Degeneration is a disease that affects your central or straight ahead vision. Also known as Age Related Macular Degeneration.

Meibomian Gland A gland located within the eyelids which secretes and oily layer of tear fluid.

Myopia or nearsightedness is when the images of distant objects appear blurred. The eyeball is too long for the normal focusing power of the eye.

Pachymetry is the measure of the corneal thickness. The thickness is important for people considering LASIK surgery and people at risk for glaucoma.

Photophobia Abnormal sensitivity to light.

Presbyopia A gradual lessening of the eye’s focusing ability at near due to age related changes of the eye.

Progressive Lenses are  often referred to as  “no line bifocal.” Unlike a bifocal, where there are two distinct areas of vision, near and far, progressives have an unlimited amount of areas as you look from distance to near in the lens.

Pterygium A disease of the eye in which a triangular fold of tissue extends form the conjunctiva into the cornea.

Pursuits Slow, smooth eye tracking

Saccades fast reading eye tracking

Strabismus is a condition in which both eyes do not look at the same place at the same time. It is sometimes referred to as crossed eyes. Poor eye muscle control usually causes crossed-eyes. If untreated, strabismus can lead to amblyopia.

Subconjunctival Hemorrhage presents as a bright red spot on the white of the eye, often without a known cause.

Tonometry measures the Intra-Ocular Pressure (IOP) or the pressure inside of the eye.

Topography  A corneal topographer is an instrument that maps the shape of the cornea, and gives information much like that of a topographical map for hiking. This useful for specialty contact lens fits and refractive surgery.

Transition Lenses are the kind of lens that change to dark outside. and back to clear indoors.

Vitreous Humor is a gel-like substance that fills most of the eye.