The eyes are complex organs that can be affected by many diseases. Blurred vision, double vision and blindness are common symptoms of eye diseases that are experienced by thousands of people each year. Common diseases such as cataracts and glaucoma are diagnosed daily. There are some eye diseases, however, that are extremely rare and are diagnosed in very few individuals. These strange eye diseases can result in unusual symptoms, such as absence of eye color, visual hallucinations and abnormal eye movement.
Aniridia
Aniridia is a congenital eye disease that is characterized by the complete or partial absence of the iris, the colored portion of the eye that surrounds the pupil. Aniridia is believed to be a result of a deletion on chromosome 11, according to the Aniridia Foundation International. In approximately two-thirds of anirida cases, at least one parent has the condition as well. In addition to absence of the pupil, people with anirida often experience cataracts, lens dislocation, glaucoma, nystagmus, which is involuntary movement of the eyeball, and corneal pannus, which is scarring of the corneal tissue. All of the characteristics associated with aniridia lead to vision reduction.
Charles Bonnet Syndrome
Charles Bonnet syndrome is an acquired eye condition that causes visual hallucinations in people with existing vision problems. The disease usually affects older adults who have lost their vision, but can affect people of any age. The exact cause of Charles Bonnet syndrome is still being researched. There are usually two different types of hallucinations. The first type is a complicated series of patterns and lines. The second type is entire scenes of people and places. Hallucinations can be black-and-white, in color, still or full of movement. There is no treatment or cure for Charles Bonnet syndrome, but visual hallucinations usually disappear on their own in 12 to 18 months, according to the Macula Vision Research Foundation.
Duane Syndrome
Duane syndrome is a congenital eye disorder that is characterized by problems with eye movement. Eye muscles contract when they shouldn’t and do not contract when they should. The condition is usually diagnosed by age 10 and is more common in females than males, according to the National Human Genome Research Institute. Those with Duane syndrome usually have a limited ability or inability to move the eye outward toward the ear and inward toward the nose. In most cases, only the left eye is affected, but the disease may affect both eyes. The exact cause of Duane syndrome is unknown, but is believed to be a combination of genetics and environment.
