The connections between the eye and the brain have been well known and established for centuries. Indeed in a sense the eye is a part of the brain. Often described as the window of the soul, the eye can actually be a window onto our cognitive and neurological functions, being a visible and accessible organ that frequently reflects changes in the larger network.
Conditions such as Alzheimer’s disease, Parkinson’s disease and even Multiple Sclerosis can have eye-based indicators. On a more basic level, the excessive avoidance of eye contact can be suggestive of autism. With roughly 83% of our perception, learning, cognition and activity mediated via sight, the eye is by far our most important sensory organ.
Across the globe eye disease is reaching epidemic proportions. According to a study published in The Lancet last year, in 2015 36 million people worldwide were blind, while a further 217 million were suffering from moderate or severe distance vision impairment. Glaucoma in Asia and Africa is a huge problem that is still on the increase, but the shocking (if hopeful) fact is that 75% of visual impairment is avoidable. 1.1bn people are vision impaired because they don’t have access to spectacles. That is a failure of social, economic and political causes rather than a scientific one. In the meantime, the development of new treatment methods and technology could see the possibilities for full and partial restoration of sight increase dramatically over the next few years.
Rohit Varma, MD, MPH, is a world leader in the study of eye disease. He has recently been researching new imaging techniques in early diagnosis of glaucomatous optic nerve damage and is involved in developing implantable intraocular pressure sensors and drainage devices. He is particularly concerned with studying eye disease in minority populations.
Elsewhere, implantable visual prosthetics have been developed by companies in California (Second Sight), Germany (Retina Implant AG), and France (Pixium Vision), while ground-breaking trials have been carried out in the UK. In 2015, Manchester surgeons restored partial sight to a blind, 80-year-old sufferer from age-related macular degeneration (AMD) using a visual prosthetic, while in 2016 a blind woman was successfully given a “bionic eye” at Oxford Eye Hospital.
So-called bionic eyes stimulate the brain with light from a tiny video camera, but scientists have also begun researching ways to restore vision by working directly on the brain, bypassing the eye altogether. We perceive patterns of light as a result of electrical impulses delivered to the visual cortex. On this basis, Second Sight has begun developing a device that generates similar electrical signals and hopes to recreate some degree of visual perception without working on the eye at all.
In recent years we have seen a huge and helpful boom in smartphone apps to diagnose medical disorders. The applications have also been employed in treating eye conditions. Peek Retina is a portable ophthalmoscope in the form of an app on your phone that can be used to capture and record retinal images and to measure visual acuity. It has been successfully used in diagnosis in remote areas such as sub-Saharan Africa.
EyeNetra meanwhile have developed a diagnostic device for easily spotting refractive errors. A headset is combined with an app to flag up errors in perception and to recommend the correct eyeglass prescription.
Advances in treatment of the eye could also be made possible using the CRISPR-Cas9 gene editing technique. CRISPR has been used to repair a genetic mutation producing retinitis pigmentosa in induced pluripotent stem cells from a patient suffering from the disease. Research at the Center for Genome Engineering at the Institute for Basic Science suggests that CRISPR can be used to correct the effects of non-hereditary conditions as well as inherited ones, following gene surgery on mice suffering from AMD.
It is to be hoped that research will provide us with a better understanding of the connections between the eye and the brain, and the way in which vision works, as well as providing practical solutions to the widespread problems of blindness and vision impairment. Speculation that virtual reality technology might one day be able to recreate our full field of vision within the visual cortex may seem far-fetched but is not beyond the bounds of possibility. Whether brain diseases and even mental illness can ever be treated using similar methods remains to be seen. When we recall that what we see is an interpretation of the world rather than the world as it is, it may be thought that problems of adjustment and understanding could be literally related to how we see things after all.