A recent study published in Translational Vision Science & Technology (TVST) demonstrates certain intriguing aspects of a rather mysterious area of the brain. The results could hold great implications for neurodegenerative diseases such as Glaucoma and Alzheimer’s, opening up new avenues for research into novel neuroprotective therapies.

Glaucoma And The Brain

Glaucoma is a neurodegenerative disease which causes patients to lose their vision and may lead to blindness. These random losses are different to the blind spots that appear after a stroke or brain tumor. It was thought, till recently, that the progression of glaucoma was independent, or uncontrolled, by the brain.

However, researchers found evidence last year that suggested otherwise – the brain was involved. More specifically, it was observed that patients with moderate to severe glaucoma sustained vision in one eye while it disappeared in the other; something similar to pieces of a puzzle they referred to as the ‘Jigsaw Effect’.

According to lead author, William Eric Sponsel, MD, of the University of Texas at San Antonio, Department of Biomedical Engineering, this indicates some level of communication between the brain and the eyes that scientists were previously unaware of.

Latest Findings And Skepticism

In their latest paper, ‘Refined Frequency Doubling Perimetry Analysis Reaffirms Central Nervous System Control of Chronic Glaucomatous Neurodegeneration’, Sponsel and colleagues discovered that the Jigsaw Effect began during early stages of glaucoma. They also found clues pointing towards the specific part of the brain optimizing vision as the disease progresses.

Since these findings challenge longstanding assumptions regarding glaucoma, they have faced certain skepticism. Glaucoma experts have raised concerns – Paul Artes, PhD, of Plymouth University, Department of Eye and Visual Sciences along with Jonathan Denniss, PhD, University of Nottingham, Visual Neuroscience Group stated that if the brain was involved, vision in both eyes should improve rather than a ‘mix and match’ scenario. They claimed that analyzing vision in both eyes of different patients did not reveal any visual advantage in one eye as compared to vision in both eyes of other patients.

Sponsel and his research team state otherwise, claiming that their data, and that provided by other experts, conclusively demonstrated the ‘Jigsaw Effect’. They highlighted that the alternative analytical method the experts were using could not effectively detect computer-generated complementary visual field pairs. “The drawback in their approach was the assumption that a single brain could somehow combine information from the eyes of various human beings. We studied individual people with naturally paired eyeballs connected to a single brain”.

The Structure Involved In Controlling Vision Loss

Co-author Ted Maddess, PhD, of the Australian National University, Center of Excellence in Vision Science revealed that small-scale, arc-shaped patterns of vision expressed by patients led to the discovery of the vital region of the brain that coordinates vision loss. These patterns resembled structures present at the back of the brain – ‘ocular dominance columns’. Even though there function is not completely understood, it is known that some are associated with the right eye and some with the left.

The Significance Of Ocular Dominance Columns

Sponsel suggests that fine spaces between ocular dominance columns, associated with the right and left eye, are where coordination of the working field of vision takes place. Depending on the brain’s preference, these spaces can function with either eye – like a bilingual person.

This suggests that the progression of other neurodegenerative diseases, such as Alzheimer’s and Parkinson’s diseases, might also be actively controlled by the brain. “Our work demonstrates that the brain will not let us lose control of the same function on both sides of the brain, if that can be avoided”, Sponsel explained.

The team believes that if this role of neurodegenerative regulation by the brain is highlighted, largely unexplored processes and opportunities for controlling disease progression can now be studied.