Acuity

Clearness of vision. Standard is 20/20 which means the individual see at 20 feet what they should be at that distance.

Accommodation

Ability to change and control the focusing of the eye.

Astigmatism

Condition where vision is distorted because the front of the eye is not totally spherical, i.e. it is shaped more like a football than a soccer ball. Clear vision is restored by an appropriate lens.

Binocular

Using both eyes together

Convergence

Turning of the eyes inward to see closer

Fusion

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

Hyperopia

Farsightedness. It is easier to see in the distance than close up. A small amount of far-sightedness is normal in children but may affect their comfort and concentration at close distances, i.e. reading and writing.

Myopia

Shortsightedness. It is easier to see close up than in the distance.

Motilities

Movement of the eyes following a moving target.

Multifocal

A lens with an upper area for seeing in the distance and a lower area with a different prescription for close work.

Minus Lens

(Concave) Changes the path of light so that the focus is farther way. Given to correct shortsightedness.

Perception

Interpreting the information received by the eyes.

Plus Lens

(Convex) Changes the path of light so that it focuses closer. Given to correct far-sightedness.

Presbyopia

Condition associated with normal aging, resulting in difficulty reading at close distances.

Stereopsis

Ability to see depth and judge distance.

Vergence

Turning of the eyes to see singly at a given distance.