Transparent colorless mass of soft, gelatinous material filling the globe of the eye between the lens and the retina.

Persons who have some difficulty seeing with one or two eyes even when wearing glasses.

Measurement of the ability of the eye to perceive the shape of objects in the direct line of vision and to distinguish detail; generally determined by finding the smallest symbol on an eye chart that can be recognized at a given distance.

The ability to correctly perceive an object or letter of a designated size from a distance of 20 feet; normal visual acuity.