A congenital condition is one which the sufferer is born with, or which appears soon after birth, and nystagmus is a disorder in which involuntary eye movements occur. The eyes of a person with congenital nystagmus, also known as infantile nystagmus, most often move, or sometimes jerk, from side to side in an uncontrollable manner. In some cases, the eyes move up and down or rotate. Although the condition is usually lifelong, the eye movements do not make the surroundings appear to move and people with congenital nystagmus are usually able to read and live normal lives. Clearness of vision is typically affected but this may not be severe enough to prevent a person from driving.
Congenital nystagmus is not always diagnosed immediately, but becomes apparent within the first six months of life. Although the condition is easily recognized, it may be missed because new babies spend a lot of time sleeping and the eyes may not be open for long periods at first. Nystagmus is only classed as congenital if other causes have been ruled out, such as brain tumors or diseases affecting the optic nerve or retinas.
Many people with congenital nystagmus experience what is known as a null point, where abnormal eye movements are reduced, or stopped, when they gaze in a particular direction. The null point can be used when a person with congenital nystagmus is reading, because turning the head and the eyes in a certain direction can help to increase clarity of vision. Sometimes surgery is carried out to treat the disorder, and the eye muscles are moved so the null point occurs when the eyes are looking straight ahead.
The rate and degree of the eye movements in congenital nystagmus often increase when a person is unwell, tired or anxious, or trying to fix the gaze on something. In some people with congenital nystagmus, bobbing and shaking of the head are seen to occur, but this tends to subside over time. The movements of nystagmus typically decrease when people look at objects close to them. Shutting the eyes reduces the abnormal eye movements, and they stop completely during sleep.
In adults, treatment of congenital nystagmus with drugs such as gabapentin can diminish the speed and size of abnormal eye movements and reduce vision impairment. Wearing contact lenses may also be helpful in some cases. Surgery is not always beneficial, and the risks of anesthesia and possible sight loss have to be weighed against the chances of improvement.