Eyes normally move only in response to stimuli or direct commands from the brain. If severe, rapid involuntary eye movements may interfere with vision. Rapid eye movement, or REM, can occur as a natural process or as a symptom of disease. It may indicate a serious brain disorder or occur naturally in sleep. Nystagmus -- one type of REM that can appear as shaking, jittering, side to side or up and down movements -- is a symptom of disease.
One of five sleep stages and characteristically the most active stage physically is REM sleep. Dreaming occurs in the REM stage. Rapid eye movements and muscle twitching are accompanied by an increase in heart rate and breathing rate. Some muscles, on the other hand, become paralyzed. The average person goes through five sleep cycles each night, with REM sleep lengthening during each cycle. People enter REM stage faster and stay there longer as they age, Healthcommunities.com reports.
Onset of congenital nystagmus may appear as early as six to eight weeks of age as a congenital condition often associated with congenital vision loss, according to Richard L. Windsor, Doctor of Optometry, on his website, The Low Vision Gateway. Around one in 1000 infants has nystagmus, with 80 to 90 percent having severe vision loss and 10 to 20 percent having mild vision loss. Diseases that affect vision, such as albinism, optic nerve hypoplasia, congenital cataracts and retinopathy of prematurity can cause congenital nystagmus, according to Windsor. The eyes swing rapidly back and forth like a pendulum. Nystagmus that starts early may improve somewhat during adulthood.
Acquired nystagmus often occurs as a consequence of neurological or brain disorders, Windsor explains. Vision loss in adults doesn't normally cause nystagmus as it does in infants and children, he adds. The movements of acquired nystagmus can cause vertigo and dizziness, a condition called oscillopsia. Head injuries, brain tumors, stroke and conditions such as multiple sclerosis may cause acquired nystagmus. Inner ear problems such as Meniere's disease may also cause nystagmus. The movements of acquired nystagmus often include slow eye movement to one side followed by rapid movement back.
Anti-seizure medications such as Dilantin and Phenobarbital may cause nystagmus and oscillopsia. Vertical nystagmus, an up and down movement of the eyes, may be described as a rolling vision sensation, Windsor reports.