A clinical study conducted by researchers at Oxford University explored the use of a gene therapy to treat the eye disease, choroideremia.

Results of the 2011 study, demonstrated vision improvements in five out of six patient participants. One patient improved from 20/300 vision to 20/120 vision after treatment. Another enjoyed an improvement from 20/80 to a very functional 20/40.

Both of these patients had lost their central, straight-ahead vision due to advanced retinal degeneration caused by the retina disease, choroideremia.

What is choroideremia?

Choroideremia (CHM) is a rare, inherited retina disorder that causes degeneration of the choroid layer and the pigment cells and also, the photoreceptors in the retina tissue on the back, inner wall of the eyeball. It almost always occurs in males and begins in the childhood years. CHM affects about 1 in 50,000 individuals.

Choroideremia symptoms

Symptoms of CHM include ongoing decrease in vision, starting from barely noticeable, then deteriorating to the level of legal blindness. Night blindness is often the first symptom.

The layers at the back of the eye that are affected by CHM are the choroid, the pigment layer and the rods and cones – the latter two being layers in the retina.

Choroideremia gene therapy

The choroideremia gene therapy involves a surgical, subretinal injection of healthy retina cells.

During the surgery, the fovea, the central portion of the macula where pinpoint central focusing vision is achieved, is deliberately detached by the surgeon’s sub-retinal fluid injection.

The therapeutic fluid that is injected contains healthy cells that are inserted into adeno-associated virus (AAV). The virus is designed to “infect” the damaged choroid and retinal tissue with the healthy therapeutic cells, thus rebuilding the damaged tissue.

The Foundation Fighting Blindness, where Dr. Deupree is a committee member, has provided funding for two decades to help make choroideremia gene therapy studies possible.

Other choroideremia gene therapy studies and trials are in early planning stages around the world including in UK, Canada and in Philadelphia, Pennsylvania in the United States.