Amblyopia/Lazy Eye

Commonly known as Lazy eye. A loss of vision in a young child due to the eye not being used. The eye is normal but the brain tends to suppress or ignore the image received by the amblyopic eye. The most common causes include a muscle imbalance, a focusing problem, or a problem such as a cataract or corneal scar. Sometimes both eyes can be affected.


Condition in which the two eyes have unequal refractive error. One of the major causes of amblyopia. This is a "hidden" cause of amblyopia and very difficult to detect without an eye exam.


An absence of the lens in the eye. The lens is removed during a cataract operation. The natural lens may be replace with an artificial lens during the cataract operation.


An irregular curvature of either the cornea (front of the eye) or the lens. If either structure is shaped more like a football rather than a basketball, light is not sharply focused on the retina. This results in blurry vision for both distance and near.


An opacity or haziness of the lens of the eye. It may or may not reduce the vision depending on size, density and location. If a cataract reduces visual acuity significantly, an Ophthalmologist can replace the defective lens with an artificial lens.


The front part of the eye that acts as a window for the entrance of light rays. It is attached to the other outer coat of the eye, the sclera; the white part of the eye. The cornea provides a significant amount of focusing power for the eye (the rest is provided by the lens). Because it has many nerve fibers, an injury or foreign body causes significant pain and discomfort.


The unit used to measure the amount of refractive or focusing power of the eye. It also refers to the strength of lens required to provide clear vision. In general, the higher the refractive error, as measured in diopters, the worse the eye.


Commonly known as double vision.


A tendency for an eye to turn inward a little bit. It occurs under certain conditions such as fatigue.


Commonly known as "crossed eyes". One eye is constantly turned inward toward the nose.


A tendency for an eye to turn outward a little bit. Occurs sometimes under certain conditions such as fatigue, bright sun light or prolonged use of the eyes.


Sometimes called "Wall Eyes". One eye is constantly turned outward.


Commonly known as farsightedness, results in close objects appearing blurry while far objects appear clear.


The colored part of the eye with a hole (pupil) in the center. It regulates the amount of light entering the eye – the dimmer the lighting the more light the iris lets into the eye by widening the pupil.


The lens of the eye is like an adjustable lens of a camera and focuses light rays on to the retina for sharp images.


Commonly known as nearsightedness, results in far objects appearing blurry while close objects appear clear.

Ophthalmologist (M.D., D.O.)

A physician (MD or DO) who specializes in the diagnosis and treatment of eye problems and diseases. The ophthalmologist works with the use of glasses, contact lenses, eye medication and surgery.

Optic Nerve

The optic nerve transmits impulses or information from the back of the eye to the brain.


A technician who fits a person for glasses. He/she does not test for glasses. Some opticians also fit contact lenses.

Optometrist (O.D.)

Doctors of Optometry are independent primary health care providers who examine, diagnose, treat and manage diseases and disorders of the visual system, the eye and associated structures as well as diagnose related systemic conditions.


A drooping of the upper eyelid. 


The pupil is the black circular hole in the center of your eye. The size of the pupil changes according to the amount of light present. It is small in sunlight and large in a dark room.

Refractive Error

If rays of light that enter an eye do not focus perfectly on the back of the eye, retina, the patient is said to have a refractive error. The main types of refractive error include myopia, when the rays of light focus in front of the retina, and hyperopia, when the rays of light focus behind the retina. When the rays of light focus perfectly on the retina, it is referred to as emmetropia. Patients who have myopia are often called "nearsighted" because they can see things only when they are close to the face. Patients that have hyperopia are often called "farsighted" because they can see things better if the objects are farther away. Glasses, also called lenses including contact lenses, are used to correct the refractive error. Usually the eyes will have similar refractive errors. When the eyes have different refractive errors; for example, one eye may have emmetropia (i.e., no need for glasses) and the other eye may have hyperopia, the condition is called anisometropia and may lead to amblyopia if left untreated.


Misaligned eyes.