Does LASIK destroy your circadian rhythm?
When you’re standing in the long, winter holiday lines at Disney World, you start inventing ways to pass the time. I decided to examine whether the people who wore sunglasses also tended to be obese.
My hypothesis was: Blocking solar information from entering the eye results in a cascade of health problems that includes significant weight gain.
Neuropsin and UVA light
Our eyes use seven different proteins, called opsins, to detect light. The opsin called neuropsin responds specifically to the UVA light spectrum.
UVA is more abundant during the early morning and late afternoon — providing the eyes with a unique signal about the overall lighting conditions. Neuropsin, because of its sensitivity to UVA light, helps the retina adapt to varying light. Downstream, the retina sends light-related signals to the suprachiasmatic nucleus (SCN), a small region of the brain located in the hypothalamus, that serves as the body’s master circadian clock.
Sunglasses undermine this process by preventing UV light from entering the central retinal pathways.
In relation to weight gain, the disruption of circadian rhythms has been linked to dysfunction of the hormones that signal hunger and satiety. Mixed up day/night cycles also cause insulin resistance — which promotes fat storage.
α-MSH deficiency
Sunglasses can also cause weight gain from more than just circadian disruption.
UVB light is primarily responsible for causing the body to produce alpha-melanocyte-stimulating hormone (α-MSH), which then activates melanocytes (a type of cell that produces melanin). However, the usefulness of UVB is dependent upon pathways primed by the way UVA upregulates nitric oxide. The exposure of the eye to the UVA light spectrum kickstarts the process of renewing melanin in the human body.
A deficiency of α-MSH (caused by sunglasses blocking UVA) can:
- decrease thermogenesis (your body creating heat), promoting weight gain and fat accumulation.
- impair glucose regulation, increasing the risk of insulin resistance and type 2 diabetes — which promotes fat storage.
- lead to increased appetite and excessive calorie intake, because α-MSH is a key regulator of appetite and energy balance in the brain. It is part of the leptin-melanocortin pathway, which plays a central role in controlling hunger and satiety.
Regardless of the quality of your diet, when you put on sunglasses (or sunscreen) you are making it harder to lose weight and easier to gain it.
What else throws a tarp over the eyes?
Unfortunately, even if you ditch sunglasses, you’re still not out of the woods. Many types of contact lenses are manufactured to block UV light. In addition, permanent replacement lenses, specifically intraocular lenses (IOLs) used in cataract surgery, include UV protection.
Then there’s the problem of LASIK. I had LASIK surgery in 2020, but was stunned to learn recently that since LASIK reshapes the cornea — where neuropsin is present — the procedure could destroy these opsins. No one in mainstream ophthalmology has even considered this possibility, let alone the implications.
Post-LASIK, the eye can heal, creating new opsins through normal protein turnover and synthesis. However, LASIK fundamentally changes the cornea’s structure, which could permanently alter how UVA light interacts with neuropsin in or near the cornea. No research exists to say conclusively one way or the other. If your UVA processing is permanently damaged, you’re at risk for more than just obesity. For starters, circadian disruption has also been linked to an increase in cancers of the breast, prostate, and colon, as well as chronic pain syndromes like fibromyalgia.
As for my observational study at Disney World, the impact of Ozempic confounds my results. Public places look totally different from even a year ago, sunglasses or not. As far as my own health choices go, however, I may have been tricked, again.