As we watched with desperate hope, the members of a Thai soccer team began to emerge from a cave where they’d been trapped for two weeks. Along with relief for each boy saved was concern for their health. I wondered about what could have happened to their eyes and vision after those weeks of darkness. There hasn’t been much research into the effects of prolonged light depravation on human vision, but the good news is that animal studies indicate that the effects are temporary and reversible.
The boys’ eyes will need protection as they adapt to light because long periods of darkness can depress the production of chemicals that help dilate and constrict the pupil in response to various light levels. When the pupil doesn’t constrict well in bright light, especially sunlight, there’s a risk of retinal damage. Two weeks of poor nutrition can impact vision as well. Vitamin A is necessary for proper functioning of the human eye. The photopigment rhodopsin found in human rod cells is composed of retinal, a form of vitamin A, bound to an opsin protein which is necessary for light/dark adaption.The US Army Research Institute of Environmental Medicine investigated the effects of the lower oxygen levels occurring at high altitudes on night vision. The study was conducted over a period of two weeks and showed that lower oxygen levels impaired night vision adaption. With concern about the dropping oxygen levels in the cave, might the boys be affected similarly? Fortunately, in the Army study, night vision adaption function returned to normal when the men were at sea level and normal oxygen levels.
Photosensitive retinal ganglion cells, light sensitive cells at the back of the retina, help regulate our internal clocks, or circadian rhythm. While the internal clocks can run a little faster or slower than 24 hours, sunlight striking the retinal ganglion cells resets the clock to synchronize sleeping and waking with the natural daylight and darkness cycle. Without light, there is no reset, and the internal clock sets its own time. This can cause difficulty maintaining an accurate sense of time as well as hypersensitivity to light.
You can learn more about the eye’s response to light and how it affects our circadian rhythm with our CE, The Happy Side of Blue, at www.2020mag.com/ce.
On a brighter note, let me introduce a new contributor to Pro to Pro. Samantha Ramcharran recently received her Associates Degree in Applied Health Science from the Essex County College, Newark, NJ, Vision Care Program. She was the student representative for the program during the college’s site visit for reaccreditation. Samantha is currently an apprentice optician and studying for the New Jersey State Board exam for opticians. I welcome Samantha’s insights on education as a recent graduate of an ophthalmic program.
