by Deborah Zelinsky, O.D.
Eyeglasses may improve eyesight, but will they reduce the impact traumatic brain injury can have on a patient’s sleep? Based on a growing amount of global research, including studies and clinical experience at the Mind-Eye Institute in Northbrook, Ill., the answer is “yes.”
But, to understand the “how’s” and “why’s,” we must first explain the neurobiology of sleep and role of the brain’s hypothalamus, which is directly connected to the retina.
The sleep-wake cycle encompasses complex functions involving both internal hormonal systems (chemical signaling) and the reticular activating system (RAS), a network of neurons (electrical signaling) that emanate from the brainstem and link to the brain’s hypothalamus, according to authors of a study published in 2019 in the journal Nature and Science of Sleep. The hypothalamus not only plays a critical role in sleeping and waking patterns by regulating production of hormones like melatonin, but it is also tied to many other essential physiological functions, including body temperature, blood pressure, appetite, emotions (limbic system), motor control, and circadian rhythm. Indeed, the hypothalamus is part of what maintains the body in a condition of healthy balance. In addition to all the internal signals, the sleep-wake cycle is influenced by external stimuli, such as sunlight and blue light projected from computers.
Traumatic brain injury (TBI), as well as stroke and other neurological disorders, can disrupt the body’s balance in several ways including interrupting biochemical communications to and from key brain structures, such as the hypothalamus; directly inflicting damage on brain structures; and disrupting synchronization among eyes, ears, and other sensory systems.
Loss of sensory synchronization affects visual processing and may lead to multiple symptoms: vertigo, headaches, light and sound sensitivities, anxiousness and stress, attention and comprehension problems, an inability to read and interact normally in social situations, memory problems, and a general feeling of ”not feeling like yourself.”
Experts contend that nearly 50 percent of patients with brain injury – even those with mild TBI — experience some form of a sleep disorder like insomnia, hypersomnia (extreme daytime sleepiness), sleep apnea, and narcolepsy. Why? Because TBI oftentimes changes the brain’s responses to light, and any disruptions in those responses can impact basic physiological functions, including normal sleep patterns.
Now we’ll go back to the therapeutic role of eyeglasses and how optometry can work as an adjunct profession during rehabilitation from a brain injury.
Light stimulates different types of receptors in the retina, which is composed of brain tissue and functions as part of the central nervous system. Those receptors in the retina activated by light obtain “information” from the light and “communicate” – in the form of electrical impulses – with the hypothalamus and other important brain structures.
Light governs major, internal physiological systems including circadian rhythm (which helps regulate sleep and alertness), our sleep drive, and other behaviors associated with the sleep-wake cycle. Indeed, regular shifts in lighting – from day to night – set the body’s circadian clock, “telling” us, through the release of hormones and production of internal biological chemicals, when to sleep, when to awaken, when to eat, when to exercise, when to work, and when to relax. If this normal rotation of light is disturbed, such as by flying across time zones, for example, we can experience fatigue, functional and attention difficulties, and other debilitating symptoms commonly described as jet lag. Light is even associated with body temperature and other basic functions. For example, in the dark, while we sleep, heart rate and body temperature drop, appetite is suppressed, and movement lessens.
Scientists tell us to avoid the “blue” light from computer monitors, iPads, and mobile phones before going to bed. That is because blue light blocks the retinal receptors that produce melatonin. With those receptors blocked, people do not feel as sleepy and remain alert. During the daytime, this is helpful, but blocking those receptors by using computer screens or falling asleep with a television screen flickering at night is detrimental. Even through closed eyelids, blue light can make a difference in sleep quality and brain activity. Meanwhile, some researchers suggest use of red lights before going to bed because light’s red wavelength enables more productive, refreshing sleep. Science also notes the link between light and rapid-eye-movement (REM) sleep, when noradrenaline levels change.
The goal of the Mind-Eye Institute team is to guide brain-injured patients in gaining a larger range of comfort and tolerance, as well as a quicker ability to recover from internal or external changes. With a larger range of comfort and tolerance, often symptoms decrease, and quality of life is enhanced. And one of the ways in which the Mind-Eye Institute accomplishes that goal is with therapeutic “brain” glasses, which are highly individualized and prescribed only after comprehensive patient testing. This type of eyeglass prescription is designed for activating peripheral eyesight, rather than clear, central eyesight. When the peripheral eyesight is comfortable and stable, the central eyesight becomes clearer, because depth perception and aiming ability improve.
By varying the intensity, amount and angle of light passing through the retina, “brain” glasses literally help create new information signaling pathways in the brain. These new pathways circumvent damaged or disrupted “communication” lines and re-establish more typical signaling patterns between the outside environment the retina takes in and many other brain pathways. The glasses also integrate eyes, ears, and other sensory systems and enhance visual processing, often restoring patients to a more stable sense of balance. All this is possible because the brain is readily able to change at a cellular level, meaning it can adapt to new light pathways that “brain” glasses help develop.
The investigators writing in Nature and Science of Sleep conclude that “future research should continue to focus on diagnosis and treatment questions” related to “early identification and management of sleep disorders” in brain-injured patients.
At the Mind-Eye Institute, that “future” is happening now.
Deborah Zelinsky, O.D., is a Chicago optometrist who founded the Mind-Eye Connection, now known as the Mind-Eye Institute. She is a clinician and brain researcher with a mission of building better brains by changing the concept of eye examinations into brain evaluations. For the past three decades, her research has been dedicated to interactions between the eyes and ears, bringing 21st-century research into optometry, thus bridging the gap between neuroscience and eye care. Visit www.mindeye.com/tbiquiz.