Leber Congenital Amaurosis (LCA)

Leber congenital amaurosis (LCA) is a rare type of inherited eye disorder that causes severe loss of vision at birth, affecting two to three per 100,000 births. The condition is the most common cause of inherited blindness in childhood. LCA affects both the peripheral rod cells, which allow you to see at night, and the central cone cells, responsible for fine detail and color vision.

LCA is inherited in an autosomal recessive manner, meaning that both parents must carry a defective gene for the condition in order to pass it on to their children. Each of their children has a 25 percent chance (or one chance in four) of inheriting the two LCA genes (one from each parent) needed to cause the disorder.

Babies born with LCA have very reduced vision that can often be detected by parents in the first few months of life. They may not respond to visual cues and have roving eye movements, called nystagmus. Many children with LCA habitually press on their eyes with their fists or fingers, which causes eyes to look sunken or deep set.

Less common symptoms include cataracts, corneal abnormality (keratoconus), aversion to light (photophobia), hearing impairment and developmental delays, epilepsy and motor skill impairment. Over time, the retina deteriorates; retinal blood vessels can become thin and narrow and undergo pigmentary changes.

LCA causes an abnormally low electrical response of the retina. An electro-diagnostic tests known as an electroretinogram (ERG) may be recommended to investigate how the retina is working. The electrical activity of the retina is measured under different lighting conditions to determine which part of the retina is not functioning normally. This test requires the eyes to be dilated with special eye drops. A hard contact lens in each eye is also used to measure the eye’s responses to different kinds of light.

Scientists have identified 14 genes with mutations that can each cause LCA, which account for approximately 75 percent of all cases of the disease. Using this information, scientists around the world are aiming to develop new gene therapies for LCA. In one clinical trial, a mutation known as RPE65, which accounts for about six percent of LCA, young adults with virtually no vision could, for the first time, read several lines on an eye chart and navigate in dimly lit settings after receiving a gene therapy.

Some people with LCA may also benefit from low-vision aids, including electronic, computer-based and optical aids. Orientation and mobility training, adaptive training skills, job placement and income assistance are available through community resources.

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Reviewed by health care specialists at UCSF Medical Center.

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