Ruth Van Vlear, age 15, of Dover, Del., for her question:

WHAT IS NYSTAGMUS?

Nystagmus is an involuntary, rhythmical movement of the eyes. The eyes may move from side to side, up and down, in a circle or in a combination of these movements.

The motions may be rapid or slow and jerky or smooth.

Nystagmus occurs normally when a person watches scenery from the window of a moving automobile.

Eye movement of an involuntary nature may also be caused by certain disease of the eye, the ear or the brain. Some people are also born with nystagmus.

Miner's nystagmus is a condition caused by darkness and often occurs among miners.

Vertical nystagmus is an up and down movement of the eyes while latent nystagmus occurs when one eye is covered.