Age-related Macular Degeneration (AMD) is the leading cause of blindness in developed nations and currently has no cure. The disease causes damage to the retina of the eye, preventing visual information from reaching the brain, where sight ultimately occurs. A promising new treatment is under development to restore visual function by implanting an electronic chip in the eye (retinal prosthesis). However, when patients have lost vision for many years, the parts of the brain that no longer receive signals from the eye may begin to start processing different information or even degenerate. Therefore, the success of retinal implantation ultimately depends on whether the brain is still capable of processing visual information once signals from the eye are restored. Taking quantitative measures of brain structure and function before and after implantation, we will ask questions with both clinical and scientific impact: 1) Can we use neural measures in the brain before treatment to predict the success of retinal implants in restoring sight? 2) How does restoration of visual inputs affect brain structure and function? In answering these questions, we will provide important prognostic information for treatment with retinal prosthetics and gain a better understanding of brain plasticity.
Age-related Macular Degeneration (AMD) is the leading cause of blindness in developed nations and currently has no cure. The disease causes damage to the retina of the eye, preventing visual information from reaching the brain, where sight ultimately occurs. A promising new treatment is under development to restore visual function by implanting an electronic chip in the eye (retinal prosthesis). However, when patients have lost vision for many years, the parts of the brain that no longer receive signals from the eye may begin to start processing different information or even degenerate. Therefore, the success of retinal implantation ultimately depends on whether the brain is still capable of processing visual information once signals from the eye are restored. Taking quantitative measures of brain structure and function before and after implantation, we will ask questions with both clinical and scientific impact: 1) Can we use neural measures in the brain before treatment to predict the success of retinal implants in restoring sight? 2) How does restoration of visual inputs affect brain structure and function? In answering these questions, we will provide important prognostic information for treatment with retinal prosthetics and gain a better understanding of brain plasticity.
Three out of five potential patients were recruited successfully (the other two opted out). Pre-implantation data collection is complete (January 2016). YNiC ethics permission has been granted to collect similar data from age-matched controls (May? 2016). Data collection on controls has begun and will finish by September 2016. Follow-up data collection on three patients post-implantation is expected beginning October 2016, to be completed by January 2017.Update, 23 October 2017Data collection is complete. Three patients (out of five possible) were scanned pre-implantation, and one 13 months post-surgery. Of the other two, one is deceased and the other declined. Control data have been acquired on ten age-matched (elderly) participants using the structural protocol (cortical myelin and thickness), ten controls on the functional protocol and nine controls for the spectroscopy (GABA neurochemical level) protocol. Key findings are summarised below:Primary outcomes (safety and feasibility): All scans were completed safely without any adverse events. In the patient that completed follow-up, MRI scanning had no adverse effects on retinal prosthetic implant function.Secondary outcomes (MR measures):Structural MRI: In the AMD patient that completed the study, mean cortical thickness in early visual areas (V1, V2) was thinner than in age-matched controls, but increased between pre- and post-implant scans. Cortical myelin levels were also slightly lower in the patient than in controls, and also increased post-implantation in V1, but not in V2.Functional MRI: Pre-implantation responses in visual cortex were robust in the parafoveal stimulus representation, consistent with the patient's behavioural responses, but there was no response in the occipital pole to suggest cortical reorganization. However, there were no measurable functional responses post-implantation, most likely due to occlusion by the cable extending from the electrode array chip over the retinal region that was tested pre-implant (also verified behaviourally). In the future, care must be taken to check with the surgeon pre-implantation in order to select a retinal region that will remain unobstructed following implantation.Magnetic resonance spectroscopy (Neurochemical GABA measures): Preliminary analysis of MRS data in the patient suggest pre-implantation GABA levels in visual cortex were comparable to age-matched controls. However, further analysis is required to confirm these values.Comparison with clinical measures of visual function: We are currently conducting this analysis.
UPDATE 12/7/18: A manuscript including part of these data has been submitted to but rejected from Science, New England Journal of Medicine and most recently, Ophthalmology. ('First-in-Human Integration of Natural and Artificial Vision:
Electronic Retinal Prosthesis Trial'). We are considering publishing our findings separately from the linked clinical trial in Manchester.
Status | Finished |
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Effective start/end date | 1/02/15 → 31/01/17 |
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