Vacation, TV Interview Reminders of How Light, Sleep Linked
I completed several days of much needed vacation in July, and that was followed recently by a WGN-TV interview on glaucoma. Glaucoma is one of the leading sources of blindness in this country. It acts by increasing pressure inside the eye, which, in turn, damages the optic nerve and results in loss of eyesight. The two events – vacation and interview — were totally unrelated, yet both made me consider the important connections and interactions between healthy eyes – more specifically, healthy retinas — light, and normal sleep habits.
Two recent glaucoma studies in the Journal of Glaucoma show a strong relationship between the eye disease and peculiar sleep patterns, thus linking glaucoma to circadian rhythms which play an important role in sleep. Just consider the disruption jet lag can have on a sleep cycle.
According to a 2019 study, nearly 6,800 patients with glaucoma and corresponding visual field defects completed a sleep survey. From their responses, researchers discovered an association between glaucoma and poor sleep architecture, including sleep of abnormal duration and latency, as well as excessive daytime sleepiness. In the second scientific article, published in 2020, experts reported that “impaired perception of light input due to glaucoma can subsequently lead to abnormal serum levels of melatonin, resulting in circadian rhythm misalignment. This disruption of the circadian rhythm also contributes to sleep and mood disorders, both common in individuals with glaucoma.”
Research has even provided evidence that retinopathy, a disorder usually related to problems with blood vessels in the eyes, can cause a decline in memory and thinking skills. Fragile or damaged blood vessels modify the way in which our eyes perceive light.
As for my vacation, I was enjoying plenty of relaxation and much needed sleep, sleep, zzzz, until I forgot to turn off some lights one night. Light activates the retina — even through closed eyelids — and keeps it continually sending environmental signals to the brain. My sleep was interrupted as a result; I did not awake refreshed. How many readers of this blog are aware that light in the blue spectrum – the kind of light emitted by common LEDs, including those pesky, glowing pinpoints of light from electronic gizmos like television cable boxes – can create sleep problems? I learned my lesson and the next night turned the lights off and placed a book up to block the small, electronic LED light source in my room.
A bit of scientific explanation may be in order here.
The retina is composed of brain tissue and functions as part of the body’s central nervous system. For this reason, all body processes connect with the eye in some way, including the portion linked with circadian rhythms. The light triggers electrical signals that propagate through nerves.
In fact, the retina helps route information through many different pathways to the brain’s cortex. Retinal processing is one part of visual processing. Visual processing refers to that almost-instantaneous ability of the brain to take in multiple sensory signals (from eyesight, hearing, smell, taste, and touch) at all levels – unconscious, subconscious, conscious; meld them with one’s internal sensory signals; and then process the information to end up with a response. Retinal processing plays a critical role in the integration of various senses, including eye-ear coordination, as well as the regulation of physiological processes, which. in turn, influence motor control, biochemical activity, and perception.
The retina not only transmits environmental signals through eyesight at a conscious level but also from the external luminance and movement at a subconscious level. Concurrently, the retina receives feedback signals from the body. This continual process of feeding forward sensory signals from the environment and receiving feedback signals from various brain structures makes the retina a two-way portal for influencing and monitoring such processes as posture, movement, and thinking.
At the Mind-Eye Institute, we are able to prescribe individualized, therapeutic “brain” glasses, colored filters, and other optometric interventions to help patients redevelop visual processing skills during recovery from brain injuries and neurological disorders, including stroke. The lenses are also used to build new processing skills in patients labeled as having “learning differences.” Brain glasses bend light entering the retina in different ways, varying its intensity, angle, and amount in an effort to bring patients relief from a variety of symptoms.
My advice: turn off the lights when you go to bed – ALL the lights – even if that means throwing a cloth or propping up a book over the tiny LED light glowing from some electronic equipment in the corner of your room. Your retinas want to rest, and the rest of your brain needs no outside influence – and communication chatter — from light to interrupt its work while you sleep. Sleep is the time when the brain sorts and consolidates memories, strengthens neuronal connectivity and activity, and clears out the metabolic waste that it has accumulated throughout the day. So, don’t interfere with its processing.
Also, remember to schedule an annual eye examination. Disorders like glaucoma oftentimes have few, if any symptoms, until irreparable eyesight damage has occurred.
And, of course, sleep well tonight.
Deborah Zelinsky, O.D.
Founder, Executive Research Director
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