A Visionary Approach
(January 10th, 2014) Blindness caused by retinal degeneration is untreatable, but new research from Tübingen University, Germany, suggests that neuroscience's current favourite method, optogenetics, may one day help blind people see again.
Retinitis pigmentosa (RP) is the name given to a group of inherited conditions of the retina leading to a gradual progressive reduction in vision over many years, and eventual blindness in about 1/4000 people. Usually, difficulties with night vision and peripheral vision are noticed first, and then detailed, colour and central vision are affected later. At present, there is no cure for RP, but over the last 10 years optogenetics, or the expression of light-sensitive proteins in retinal neurons, has emerged as a potential treatment for sufferers of RP.
Thomas Münch from the Centre for Integrative Neuroscience at Tübingen University explains: “Animal studies suggest that optogenetic approaches hold a lot of promise to restore light sensitivity of the retina and therefore vision of the affected individual. For the further development of this method it is essential to examine the possibilities and the limitations of vision restoration when expressing optogenetic proteins. This would allow assessing the efficacy of novel treatments in restoring the diversity of human visual processing.”
In a recent publication, Thomas Münch and his student Marion Mutter used a computer model to do just that. The results of the model showed ways in which the biophysical properties and expression levels of the channelrhodopsins (light sensitive ion channels) can be changed to increase their operational range, rather than them only working in the brightest of sunlight, as currently is the case. Moving forward Thomas Münch’s group “is working on expressing optogenetic proteins in human retina in vitro so that 'normal' responses of human retina can be compared to 'optogenetic vision'. This knowledge will help to further optimise optogenetic treatments of patients in projected clinical trials.”
Perhaps the importance of this research can be understood by looking at the difficulties sufferers of this condition face. Noel Hemmings, one sufferer, and Assistive Technology Coordinator for Action for Blind People (UK) tells me, “I started to suffer symptoms around 11 years old and was told, in no uncertain terms, that nothing could be done and eventually I would go blind. At about 19 years old ‘I came out as being visually impaired’ and since then the RP has crept up on me slowly but relentlessly and I now have very little usable vision.” Despite having received mobility training, a white cane and a guide dog which enables a relatively good and independent life he confesses that “having sight loss has its drawbacks: knowing I'll probably never be able to drive, difficulties in shopping alone” and most shockingly “an inability to go into busy bars since in the past I have been punched and beaten simply for walking into somebody or spilling their drinks (it's usually a while before they notice the white stick)”.
Noel is just one of many people who may benefit from Thomas Münch’s group’s work, and might one day lead a normal life again.