The eye is a key element in vision, but it is not the only element. Neural signals generated by the eye are transmitted to the brain, processed, and translated into vision.
“The brain deserves a better reputation in ophthalmology,” said Bernhard A. Sabel, PhD, director of the Institute of Medical Psychology, Otto von Guericke University of Magdeburg, Germany. “Because we are so eye-focused, we don’t very often think of what lies behind the eye, the brain, and the role it plays in vision.”
Damage from glaucoma and other visual diseases is seldom complete, he continued. Most patients show residual vision, areas of good function, partial function, and no function. Just as physical therapy exploits neural plasticity to improve residual function following stroke or other injury, he exploits neural plasticity to improve residual vision.
In normal vision, the brain amplifies and processes retinal signals to produce vision. Electroencephalograms show that normal visual-processing networks are disrupted in blind individuals. Specific frequencies of alternating current stimulation to the eye and the brain for 20 to 40 minutes daily over 10 days or longer can induce the brain to create alternate processing pathways and improve vision impaired by glaucoma.
Early stage clinical trials showed a 24% improvement in visual field and 60% improvement to impaired visual field sectors. About a third of patients were non-responders, while 70% reported subjective improvement to their vision. A few patients reported mild headache and there were no serious adverse events.
Dr. Sabel noted that electrical stimulation is not currently reimbursed by national health plans, but some commercial plans cover treatment.