What Eye Problems Result from Albinism
People with albinism, whether it involves the eyes alone or involves the skin and the hair, often have several problems:
People with albinism are not “blind,” but their vision (also called visual acuity) is not normal, and cannot be corrected completely with glasses. Extreme far-sightedness or near-sightedness, and astigmatism are common (see definitions below) and correction with glasses can improve acuity in many people with albinism. Corrected visual acuity ranges from 20/20 (can see at 20 feet what should be seen at 20 feet; normal) to 20/400 (see at 20 feet what should be seen at 400 feet; legally blind). Normal or near-normal vision is unusual, however, even when glasses are worn.
- Nystagmus (nye-STAG-muss), which is an involuntary movement of the eyes back and forth. Many people with albinism learn to use a head tilt or turn that decreases the movement and may improve vision.
- Strabismus (strah-BIZZ-muss), which means that the eyes do not fixate and track together. Despite this condition, people with albinism do have some depth perception, although it is not as sharp as when both eyes can work together. Strabismus is common in albinism and is related to the altered development of the optic nerves. The strabismus in albinism is usually not severe and the tends to alternate between involving the right and the left eye.
- Sensitivity to light, which is called photophobia (FOE-tow-FOE-bee-ah). The iris allows “stray” light to enter the eye and cause sensitivity. Contrary to a common idea, this sensitivity does not limit people with albinism from going out into the sunlight.
- Iris color is usually blue/gray or light brown (Diagram 1). It is a common notion that people with albinism must have red eyes, but in fact the color of the iris varies from a dull gray to blue to brown. (A brown iris is common in ethnic groups with darker pigmentation.) Under certain lighting conditions, there is a reddish or violet hue reflected through the iris, which has very little pigment. This reddish reflection comes from the retina, which is the surface lining the inside of the eye. This reddish reflection is similar to that which occurs when a flash photograph is taken of a person looking directly at the camera, and the eyes appear red. With some types of albinism the red color can reflect back through the iris as well as through the pupil.
One major abnormality of the eye in albinism involves lack of development of the fovea (also known as foveal hypoplasia) The fovea is a small but most important area of the retina in the inside of the eye. The retina contains the nerve cells that detect the light entering the eye and transmit the signal for the light to the brain. The fovea is the area of the retina which allows sharp vision, such as reading, and this area of the retina does not develop in albinism. It is not known why the fovea does not develop normally with albinism, but it is related to the lack of melanin pigment in the retina during development of the eye. The developing eye seems to need melanin for organizing the fovea.
The major normality of the eye in albinism involves the development of the nerves that connect the retina to the brain. People with albinism have an unusual pattern for sending nerve signals from the eye to the brain (Diagram 3). The nerve connections from the eye to the vision areas of the brain are organized differently from normal (see Diagram 3). This unusual pattern for nerve signals probably prevents the eyes from working well together, and causes reduced depth perception,