Choroideremia is a condition characterized by progressive vision loss that is commonly seen in males. It is a rare, inherited, progressive eye disease that causes degeneration of the retina and blindness. It is an X-linked condition that may affect several members of the same family. Choroideremia damages the retina and the network of blood vessels behind the retina called the choroid. The choroid, retinal pigment epithelium (RPE) and photoreceptors are the major areas that are affected by this uncommon eye disorder.
The prevalence of choroideremia is estimated to be 1 in 50,000 to 100,000 people. However, it is likely that this condition is under-diagnosed because of its similarities to other eye disorders. Choroideremia is thought to account for approximately 4 percent of all blindness. However, all individuals with this condition will develop blindness, most commonly in late adulthood.
Signs and symptoms of Choroideremia
Night blindness is usually the first symptom observed because the rod photoreceptors, responsible for peripheral and night vision, are the first cells affected. Other symptoms of choroideremia include:
Symptoms of choroideremia are generally noticed about the time that a boy enters high school. However, in families where the disease is inherited, early testing may be done, and very young children can be diagnosed.
Diagnosis of Choroideremia
Checking the medical history of the family is an important part of the diagnosis, since an ophthalmologist will not be able to differentiate choroideremia from other eye diseases with a simple eye exam
. Two tests to help diagnose the condition are:
- ERG (electroretinography) measures the electrical responses of the retina
- OCT (optical coherence tomography) makes digital images of the retinal layers
Additionally, genetic testing which involves testing a blood sample
from a male can confirm a diagnosis. It can also be used to determine if a female carries the gene mutation.
Treatment for Choroideremia
There is presently no effective treatment for the disorder, but visual function can be improved with low vision aids. It is important to have your eyes monitored regularly for any changes or complications.
Medical science has discovered mutations on a gene on the X chromosome
that causes choroideremia. Research has been going on to find the right treatment. Choroideremia is one of the few retinal degenerative diseases that may be detected prenatally in some cases. Every member of a family that is affected is encouraged to consult an eye specialist
and to pursue genetic counselling. Eye doctors can provide explanations of the disease and the recurrence risk for all family members.