Measuring visual pigment regeneration to track Stargardt progression

Dr Louise Terry, Daphne Jackson Fellow, Cardiff University - £141,853

Stargardt disease is the most prevalent of all inherited macular dystrophies with visual impairment often first noticed in late childhood. Ultimately, the decline can cause a loss of all central vision. The faulty gene causing Stargardt is called ABCA4.

What is the problem?

Rods and cones, or photoreceptors, are usually able to regenerate after exposure to light. It is believed that in Stargardt disease the normal process of regeneration is slowed, resulting in a build-up of toxic waste products in the retina, causing it to degenerate over time.

What are they doing?

Cardiff University has developed a new process called imaging retinal densitometry (IRD) that measures the regeneration rate of the visual pigments in the macula’s photoreceptors. These photoreceptors undergo a chemical change when they absorb light, rendering them insensitive to light. In a healthy eye, a series of enzymatic reactions called the visual cycle reverses the conversion, enabling the photoreceptors to be light-sensitive once more. The images of visual pigment that IRD generates give an insight into how well the visual cycle is working and therefore how well the retina functions.

Overall, the fellowship will look at how fast the rods and cones decline and how quickly the toxic waste builds up in Stargardt disease. IRD images are an objective view of visual decline, taking away the dependence on patients explaining and researchers interpreting loss of vision. By comparing the images to those from more traditional methods it is hoped that early phases in the progression of visual decline might be explained.

How can this help?

Exploring how IRD can detect changes in the eyes of Stargardt patients over an 18-month period will confirm if it is a useful assessment that could be used in clinical trials. As there are potential Stargardt disease treatments in clinical trials now, IRD could provide an important measure for exploring the potential of these treatments for preserving macular function.