Ophthalmologists can be forgiven for sometimes being preoccupied with corneas, lenses, dysfunctional lenses, and even cloudy lenses. Or maculas. Or optic nerves. Any anatomic part of the eye can completely capture our imaginations and divert all our attention. I guess that shouldn’t be too surprising—it is, after all, the organ that we spend our working lives trying to protect, to repair, to heal, to improve, to preserve. How often in a day don’t we refer to the eye or parts of the eye as being a camera or likened to a camera?
The part that I want to focus on in this editorial, however, is the matter of the processing behind the eye: How does what the camera captures become part of our experience, and how is our understanding of this process changing?
Amblyopia is the first thing that comes to mind when ophthalmologists think about the brain and its impact on vision. There is nothing fundamentally wrong with the eye, but, due to a misalignment or a refractive error, the brain chooses one eye over the other. The one that is not the preferred choice becomes lazy, and the brain allows the better eye to dominate the visual sensory input. I often tell parents of a child with amblyopia that the good eye has a broadband connection to the brain, whereas the lazy eye has a slow dial-up connection to the brain. I also tell parents that there is a window of opportunity and that brain-training must be done by age 7 or 8. But is this still true today?
Neuroplasticity is the ability of the brain to make new connections, learn new things, and take on functions not normally associated with that brain area. We have been led to believe that, after the age of 7 or 8, patching will no longer work for amblyopia. Today, however, there is progress being made with computer-based games that may help improve amblyopia in adults. This sounds like science fiction, but it is possibly about to become reality.
Meanwhile, animal studies have shown that redirecting the visual input into the auditory cortex provides visual acuity of around 20/60 within 6 weeks of the fibers having been redirected. Similarly, implanting the auditory input into the visual cortex allows hearing with the visual cortex.1 Who would have thought that was possible? Patients who have suffered massive strokes can recover to a point where they seem to be functioning normally, despite having only half a brain. So, the motor and sensory functions are now in the same hemisphere?2,3 Not quite what I learned in medical school during anatomy 101. Cochlear implants are just as successful for the 80-year-old as they are for the 8-month-old. Can any of this occur without significant neuroplasticity? How and why did we ever buy into the notion that the brain was so fixed and rigid in its ways?
I predict that, within the next few years to decades, we are going to discover that our brains are the most adaptable and trainable organs in our bodies. Structurally and functionally changing our brains through mental exercises and possibly new drugs will be commonplace in the not-too-distant future. The thought of software upgrades for our brains and downloading new programs for specific purposes is not as far-fetched as we would have believed only a few years ago.
If any of this interests you, get yourself a book on neuroplasticity and see what the possibilities are. I enjoyed reading The Brain That Changes Itself, by Norman Doidge, MD. His book awakened me to what the brain’s potential could be. Of the 11 chapters, five are based on work that has led to Nobel Prizes for the scientists involved. This is serious science, even though it may sound a bit like science fiction.
Go on, give your brain a workout. Read this book and let us know what you think.
Arthur B. Cummings, MB ChB, FCS(SA), MMed(Ophth), FRCS(Edin)
Associate Chief Medical Editor
1. Hawkins J, Blakeslee S. On intelligence. New York: Times Books; Henry Holt & Co.; 2004;54.
2. Bach-y-Rita P. Sensory plasticity: Applications to a vision substitution system. Acta Neurologica Scandinavica. 1967;43:417-426.
3. Bach-y-Rita P. Brain mechanisms and sensory substitution. New York: Academic Press; 1972.