New gene injection to preserve sight in ageing eyes

Scientists have developed a technique to take advantage of a harmless virus, using it to deliver a gene into the eye to potentially save the sight of ageing people. Researchers from the US-based company Adverum are trialling the method that stimulates the organ to produce a substance that treats age-related macular degeneration (AMD).

Some 600,000 people are affected by AMD in the UK and turning the eye into its own drug-making factory could replace established treatments that have unpleasant side effects. The condition damages the macula, which is the part of the eye responsible for sharp, central vision, making it hard to discern faces or tell the time.

In most cases, the first recognisable symptoms of AMD occur in an individual’s 50s or 60s and are diagnosed through a routine eye examination. No definitive cause has been found for the condition, but it’s suspected there could be a hereditary link. Smoking, obesity and high blood pressure are also thought to be contributing factors.

Of the two forms of AMD - dry and wet - the former is the most common and occurs when a fatty substance called drusen builds up at the back of the eye. Wet AMD accounts for 15 per cent of diagnoses, which is caused by a compound called vascular endothelial growth factor (VEGF) that makes new blood vessels grow.

When abnormal blood vessels form under the retina they are prone to breaking, leaking blood and other fluids. This leads to swelling in retina cells and vision loss. It can happen very suddenly compared to dry AMD, with the condition worsening in just a few days or weeks.

Current treatments for wet AMD include having a protein called aflibercept injected into the eye once a month for life. While it blocks the action of VEGF, it can be painful and cause bruising, as well as other complications like cataracts or infection.

The new gene injection, known as ADVM-022, would only need to be administered roughly once every three years. A virus containing the genetic code for making aflibercept is introduced into the eye and acts as a vehicle to carry the genes into the organ. The genetic code then instructs cells in the eye to make the protein, enabling the eye to treat itself.