Primer on Retinitis Pigmentosa

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“It’s like walking around while looking through a narrow tube. Then at night, imagine wearing thick, heavily darkened sunglasses. The irony is that, during the day, I actually need to wear sunglasses due to my intense light sensitivity.”

James C Laird, Retinitis Pigmentosa

Imagine what it would be like to not be able to fully see a scene from your favourite TV show, to only be able to see the nose of your loved ones, to have to read your favourite book letter by letter, to live your life one jigsaw piece at a time.

This is what it can be like for those with retinitis pigmentosa (RP).

RP is a group of disorders that involve the breakdown of photoreceptor cells in the retina, a part of the eye that translates light into usable information for the brain.

This can mean that those with RP will experience night blindness (one of the first symptoms) as well as a gradual decrease in their field of view. However, because retinitis pigmentosa is caused by a change in any one of over 50 genes, each case is different. Some may have perfect central vision, but are limited to 3 degrees field of view. Others may have small patches of clarity dotted around their vision. There are even those who experience kaleidoscopic sights.

RP is an inherited disorder and can be passed on to a child by parents who do not show signs of the condition. Conversely, parents with retinitis pigmentosa will not necessarily pass on the disorder to their children.

While currently there is no cure for RP, there has been much work done to make life easier for those with the condition. Smart glasses, like OXSIGHT Crystal, are able to potentially increase the field of view for those with usable central vision allowing users to do things they were not able to previously. There has also been much research into genetics to find a way to reverse the degradation, bringing hope for a cure in the future.

For more information on RP, see RNIB’s full guide.

The state of gene therapy and stem cell treatment for blindness

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Many people in the visually impaired community are (understandably) excited about the prospect of using gene therapy and stem cells to potentially cure blindness.

While there have been encouraging developments in these fields, on the whole it is still early stages.

In December 2017, the U.S. Food and Drug Administration (FDA) approved the clinical use of voretigene neparvovec (Luxturna), the first gene therapy for any condition to be given the go ahead. This comes off the back of over 10 years of research and clinical trials, and is aimed at only those with an “inherited retinal disease caused by mutations in both copies of the RPE65 gene and who have enough remaining cells in the retina”.

There are more than 250 genes involved in the development of blindness.

When it comes to stem cells, there have been two well publicised trials involving patients with different forms of Age-Related Macular Degeneration (AMD). While the results were promising, the sample sizes were very small (7 in total) and they had only undergone the first phase of trials.

Generally it may take at least 3 trials before being submitted for approval by governing bodies. So while some may claim that these “could lead to an ‘off-the-shelf’ treatment within five years”, the timeframe makes this extremely optimistic.

In an analysis by the National Health Service (NHS), they concluded that the 2018 results from the stem cell trials conducted by University College London, Moorfields Eye Hospital and Pfizer were “in its very early stages – bigger longer term trials will be needed to be sure it’s safe and effective”. For context, the phase I trials took three years and only included two patients. Unfortunately, there has not been any more updates since.

One of the more recent trials comes from UK-based biotech company ReNeuron Group. They had started Phase I/IIa clinical trials in the US with their human retinal progenitor cell (hRPC) therapy candidate for retinitis pigmentosa (RP) earlier this year and presented some of their early findings at the sixth annual Retinal Cell and Gene Therapy Innovation Summit in Vancouver, Canada, on the 26th April.

And while progress made has been encouraging, the trials have only been conducted with three people for less than half a year each.

With number of hurdles needed to be overcome, one can only speculate when these treatments will successfully come to market, if at all.

On the other hand, technology has seen tremendous growth and plays an ever increasing role in aiding those with a visual impairment. From wearables to apps, accessories to services, there are many potential solutions out there that are able to bridge the gap until a permanent solution is found.