Gene therapy will soon be able to treat blindness

Patients who lost their vision due to a retinal degenerative disease will soon be able to see with a new gene therapy treatment.

Leber congenital amaurosis (LCA) is an inherited retinal degenerative disease caused by one or more of different genes. It is characterized by severe loss of vision at birth which progresses to complete blindness.

Children born with LCA have poor vision due to the impairment of the retina – situated at the back of the eye. The retina is light sensitive and contains receptors called rods and cones which respond to light.

This movement was enough for them to be able to navigate a maze in low to moderate light.

When the rods and cones are not working properly, the receptors send back very few messages to the brain and as a result very little or nothing is seen.

A variety of other eye-related abnormalities including roving eye movements, deep-set eyes, and sensitivity to bright light also occur with this disease.

Tests usually reveal that the retina is not functioning properly and so far there are no available treatments to make the retina function.

But science has been making advances in gene therapy and in a new first-of-its-kind therapy, scientists from the University of Iowa have been able to achieve meaningful improvement in vision of LCA patients.

In fact this therapy is currently under review by the U.S. Food and Drug Administration for potential approval this year.

Data from a controlled randomised phase 3 study shows that 93 per cent (27 of 29) of patients treated with this new therapy experienced meaningful movement in their vision. This movement was enough for them to be able to navigate a maze in low to moderate light.

There was also an improvement in light sensitivity and peripheral vision amongst these patients.

The treatment, called voretigene neparvovec (Luxturna, Spark Therapeutics), involves modifying a harmless virus to carry a healthy version of the gene into the retina.

Doctors inject millions of modified viruses into both the eyes of the patients.

However, the treatment does not restore normal vision. It does work well to allow patients to see shapes and light which enables them to move around without a cane or a guide dog.

It is also not known how long the treatment lasts but most patients have maintained their improved vision for two years.

Over 200 patients have participated in the gene therapy trials since 2007.

So far no gene therapy has gotten this close to FDA approvals and this could mean a big step forward for other gene therapies in being able to treat other genetic mutations which cause blindness – making the way for better eye health.

Source: 121st Annual Meeting of the American Academy of Ophthalmology.