Nystagmus is not a painful dangerous disease, but it may be a sign of an underlying dangerous disease. Nystagmus might lead to blurry or shaky vision but having only nystagmus doesn't lead to blindness. It does not primarily cause blindness, as it is caused by a different eye condition. If nystagmus is caused by cataract eye disease, then blindness may occur, because the cataract is one of the leading causes of blindness in the world. Cataract, which occurs in 25 million people each year, is considered to be the cause of about 50 percent of blindness.