Scientists Shed More Light on Retina as ‘Window to Brain’

Let there be light?

For years, the Northbrook, Illinois-based Mind-Eye Institute has been altering the way light is dispersed on the retina in order to create changes in the brains of patients suffering from symptoms due to traumatic head injury, concussion, stroke, and neurological disorders. Now, recent research on the relationships between light, the retina, and the brain is underscoring clinical efforts of the Institute and its founder Deborah Zelinsky, OD.

Among the latest studies is one featured in a January 2022 issue of the Journal of Clinical Medicine. There, investigators report on “retina-brain pathways of light” that can regulate a person’s mood. “Unveiling the structure and function of neural circuits related to the retina and response to light [is] crucial to better understanding how light exerts its influence on mood,” they write.

“Their findings are not at all surprising,” says Dr. Zelinsky, an optometrist world-renowned for her work in retinal processing. “The retina is composed of brain tissue and plays a crucial role as part of the central nervous system. The retina acts as a primary portal for information to the brain.” In fact, much of the focus of Dr. Zelinsky’s invited presentations at the March 2022 Congress of the Society for Brain Mapping & Therapeutics was on how assessment – mapping -- of a patient’s retina can provide much needed clues to the presence of a variety of disorders. 

Science supports her comments.  For example, authors of an article published in 2020 in Biomedical Optics Express report “optical spectroscopy can be used to explore the eye as the window to the brain” and say such assessment of the retina may help determine the severity of a traumatic brain injury. The findings “lay the groundwork for further [exploration] of…[retinal] spectroscopy for indirect non-invasive assessment of brain chemistry.”

In a 2019 issue of Somnologie (Berl), scientists contend that bright light therapy has become a useful tool in slowing progressive cognitive decline, reducing listlessness, managing sleep-wake disturbances, and addressing a number of neurological and psychiatric conditions, such as anorexia and bulimia, personality disorder, and attention deficit hyperactivity disorder (ADHD).

Meanwhile, a recent study – in the March 2022 edition of Science Advances – indicates how mitochondria – energy-producing organelles in all cells -- have a special “micro-lens” feature in the retina’s photoreceptors, particularly in the cones, and this feature affects the passage of light in these cells. The scientists suggest increased understanding of the “optical role of cone mitochondria…[has] imperative clinical implications. Noninvasive retinal imaging modalities such as optical coherence tomography (OCT) and adaptive optics…may be poised to identify mitochondria-specific deficits.”

Indeed, Dr. Zelinsky says the retina might be considered a “poor man’s MRI.”

“We are hopeful that, in the not-too-far-distant future, the modulation of optic nerve and brain activity through non-invasive retinal stimulation -- alone or in combination with other therapies -- will prove clinically effective in addressing a host of neurogenerative diseases, mental illnesses, autism, metabolic disorders, as well as dysfunctions in circadian rhythm, limbic, and endocrine systems,” says Dr. Zelinsky. 

Using therapeutic eyeglasses, filters, and other optometric interventions can stimulate retinal processing by varying the amount, intensity, and angle of light dispersed on the retina. Electrical signals, which propagate through neurons and interact with critical brain structures, affect not just the visual cortex but other, significant regions of the brain as well, like the limbic system, the cerebellum, mid-brain, thalamus, hypothalamus, and brainstem. 

“The right mix of prescriptive lenses, filters and prisms remodels the spatial and temporal distribution of light on the retina, thereby modifying the dynamic relationship between the mind’s visual inputs and the body’s internal responses. The implication is that this retinal stimulation can intentionally promote customized changes in basic physical, physiological, and even psychological systems involved in motor control, posture, emotion, and decision-making abilities,” Dr Zelinsky indicates. 

Yes, the “retina is a window to the brain,” says Dr. Zelinsky, citing the headline of an article in a 2021 edition of the journal Cell. “The retina tells us a lot about a person’s overall health.  That is why optometrists may eventually become the professionals patients initially visit to determine if they have early onset Alzheimer’s disease, high blood pressure, cardiovascular issues, diabetes, or other disorders.”  

In fact, a study involving 47,000 participants and published in a 2022 edition of the British Journal of Ophthalmology even correlates retinal health with a prediction of mortality, Dr. Zelinsky points out.