Ocular Albinism - Types, Treatment & Information
Ocular albinism is a genetic condition in which the eyes are unable to produce melanin pigment, despite normal melanin production in the skin and hair. Although the aesthetic result causes the eyes to appear more appealing with a rare light-grey/bluish/green iris, this condition can cause significant hardships due to decreased visual acuity.
Types of Ocular Albinism
There are two main types of ocular albinism that are categorized and diagnosed based on the causative gene and associated symptoms:
Ocular Albinism Type 1 – Medically known as Nettleship-Falls syndrome, or X-linked ocular albinism, this is by far the most common type. The symptoms of this disorder are more easily discernible in males, and may even go unnoticed in females.
Ocular Albinism Type 2 – Medically known as Forsius-Eriksson syndrome, this type is also usually seen in males only. However, females can be genetic carriers of the condition, and some may even display symptoms. This type is also referred to as Aland Island disease, a reference to its genetic delineation in the islands of Aland near Finland and Sweden.
Aside from the above types, there are also some individuals that have ocular albinism that is associated with oculocutaneous albinism (the more common form of albinism that causes lack of pigment in the skin and hair). This variation of albinism effects males and females equally and is usually referred to as autosomal recessive ocular albinism (AROA).
Symptoms of Ocular Albinism
The symptoms of ocular albinism vary depending on the type of the disease and the individual. People with type 1 usually complain of nystagmus – a condition that causes the eyes to move rapidly and involuntarily transiently (the symptom comes and goes). Some individuals with type 1 also exhibit sensorineural hearing loss, and researchers are currently trying to establish whether this additional symptom is just an associated effect of type 1 or whether it is caused by a different gene altogether. Individuals with type 2 frequently exhibit color-blindness and/or night blindness.
In addition to the aforementioned characteristic symptoms, all forms of ocular albinism can also cause a number of other problems, including strabismus (lazy eyes or crossed eyes), involuntary eye movement, and increased sensitivity to light. Ocular albinism also tends to cause decreased visual acuity ranging from 20/60 to 20/400. However, when the condition occurs in African-Americans vision is usually less affected, with some patients having a visual acuity score as high as 20/25. Some theorize that the increased melanin production in people with darker skin causes the affects of ocular albinism to be somewhat mitigated, resulting in better vision than that seen in patients of other races.
How Does Ocular Albinism Cause Vision Problems?
Ocular albinism makes it difficult for the eye to produce melanin pigments, which in turn results in incomplete development of the fovea during pre-birth growth stages. People with ocular albinism also have defective nerve impulse transmissions between the rear of the eyeball and the brain because of differences in the way nerve fibers develop. In a normal eye, nerve fibers are equally connected to both sides of the brain. In an eye with ocular albinism most of the nerve fibers are routed to the opposite side of the brain. Doctors can diagnose this problem using a visually evoked potential test that is similar to a brain wave test (EEG). Many of these problems are also seen in people with oculocutaneous albinism, particularly those with the autosomal recessive variation.
The Genetic Origin of Ocular Albinism
Most cases of ocular albinism are type 1 (Nettleship-Falls syndrome) or type 2 ( Forsius-Eriksson syndrome), primarily effecting males, and are linked to defects in the X-chromosome. However, the gene is actually passed down from the mother. Every time a woman with the ocular albinism x-chromosome defect has a son there is a 50% chance that the boy will be born with the disease. Mothers that carry the gene show no obvious symptoms, however they have mottled pigmentation in the rear of their eyes, which can be detected by an ophthalmologist in 80% of tests conducted. The more rare form of ocular albinism (autosomal recessive) is passed down by both the mother and father simultaneously.
Treatment of Ocular Albinism
Because the impaired vision is caused by an inadequately developed component of the eye, it is difficult to see any success with corrective lenses. However, there are some individuals with a more mild form of the disease who may be able to improve their vision with corrective lenses. Contacts are usually more effective than glasses in people that are experiencing strabismus because they enhance the full field of vision. If the condition is causing strabismus, it may be possible to realign the eyes and widen the field of vision with a surgical corrective procedure. Counseling and a change in environment may be able to provide assistance to individuals that are having social problems due to ocular albinism.