Leber congenital amaurosis

LCA is a type of inherited retinal condition (with similarities to retinitis pigmentosa). It affects about 1 in 80,000 people and is the most common form of inherited sight loss in children. LCA causes the specialised light-sensing photoreceptor cells at the back of the eye to stop working properly which causes vision loss.

Typically, symptoms start in early childhood and progress (get worse) over time. These include:

• Poor and declining peripheral vision (tunnel vision)
• Night blindness
• Shaking eyes (nystagmus)
• Poor pupil reactions

There are several different forms of LCA, each with a different cause so symptoms and speed of progression can differ between patients. Some forms of LCA are more common than others.

There are at least 20 different forms of LCA (type 1 through to type 20) that have currently been identified. Each type is caused by a defect in a different gene important for normal visual function, these genes include RPE65 (LCA 2); AIPL1 (LCA 4); CEP290 (LCA 10) and RDH12 (LCA 13). 

At the moment LCA is untreatable but a number of novel interventions are currently under investigation including gene therapy.

The aim of gene therapy for the eye is to restore aspects of vision by using a harmless virus to introduce a normal copy of a defective gene into the cells where it is needed to make it available for use, essentially ‘replacing and correcting’ the defect.

Researchers at Moorfields Eye Hospital and UCL Institute of Ophthalmology were some of the first people in the world to conduct gene therapy in the eye for LCA caused by defects in the gene RPE65. This research helped prove that gene therapy might help some people with this particular form of LCA in the future.

More research will need to be undertaken to determine to what extent gene therapy might help people with LCA and to determine what other forms of LCA might benefit from other forms of gene therapy.