A brief science of our eyes

Editor’s note: At Stripes Japan, we love to share your stories and share this space with our community members. Here is an article written by Spc. Colene Copeland from U.S. Army Garrison Bavaria. If you have a story or photos to share, let us know at japan@stripes.com.

After reviewing medical journals in encyclopedias and online, I have come to realize that our eyes are such an amazing part of our bodies. To be able to see the world through our eyes is such a gift. Vision is truly a remarkable function of living creatures. Some creatures are born without vision be it by nature, evolution or genetics (for example the eyeless shrimp or the star-nosed mole.) But most of the living organisms on this earth have some sort of sight or vision used to see the natural world around us.

The human eyeball is a sensory organ. The visual images that we see through our eyes then gets carried to our brain and translated into what we perceive is happening around us. The conjunctiva is the mucous membrane that surrounds the human eyeball except the cornea portion. In the cornea portion, there is the iris and the pupil.

Pupils dilate to let more light in and contract and get much smaller when they are surrounded by abundant light. It would harm the eyes if a lot of light got to the back of the vision channel which is the retina. The retina essentially enables vision and is basically a thin layer of tissue at the back of the eyeball by the optic nerve. This thin layer of tissue covers approximately 65 percent of the back of the eye by the optic nerve. The retina converts light into neural signals and transmit these signals to the brain for comprehending what the organism is seeing.

The optic nerve is the nerve that carries messages from the retina to the brain to transmit the messages into what the eyes are seeing and what we perceive is happening. The optic nerve has a bundle of more than one million nerve fibers. The way that the optic nerve transports these signals of vision to the brain is by electrical impulses from the eye to the brain. Damage to the optic nerve can create vision impairment, color loss, or total vision loss.

Eye color is determined by the amount of melanin in the iris. While there are exceptions to everything with the biology of the world and any combination of genetic probability can occur, people in regions of the world where it is much hotter and the sun is out a lot with barely any cloud cover, tend to have a darker eye color to protect them more from the sun. Melanin helps protect skin and eyes from direct sunlight by absorbing it better than lighter colors. Thus, melanin is beneficial to protect us more from the sun. This comes from evolution and adapting to the natural world to survive.

Regions of the world where the sun is not out a lot and there is high cloud cover from the sun with cooler temperatures tend to have a lighter eye color. This theory of eye color comes from the survival of the fittest in evolution and the most fit to their environment survives.

Color blindness is a genetic condition caused by a difference in the cells of the retina responding to light signals and then transporting these signals to the optic nerve to then send to the brain. These cells are called cones and they use wavelengths of light to be able to distinguish types of colors from one another.

A form of amblyopia is a “lazy eye.” Lazy eyes are caused by an imbalance in the position of the muscles behind the eyes. Someone can be born with an amblyopia or it can be caused by trauma to the head. A sudden lazy eye in adults can be caused by diabetes, thyroid problems or a tumor. Sometimes vision impairment is a symptom of people with amblyopia because it causes refraction differences between the two eyes because one eye may be looking in the different direction than the other eye. Sometimes an amblyopia is an easy fix with surgery and tightening of the muscles to put the eye closer in place to the other eye.

Another eye abnormality is glaucoma. Mostly found in older adults with some exceptions, glaucoma results from having too much pressure in the eye built up over time putting pressure on the optic nerve. This can cause vision impairment, vision loss and blurred vision. It is crucial to go see the eye specialist to make sure your eye pressure is in the normal range every couple of months so you can catch these signs earlier rather than later and be advised on treatments. Treatment includes prescription eyedrops, laser surgery, oral medications or a combination of these procedures and supplements.

As soldiers in the military, it is very important to take care of our eyes and keep them healthy. If we are prescribed glasses, it is important to keep them clean and wear them while reading or on the computer working so we do not put too much strain on our eyes. It is also important to keep sweat or dirt away from our eyes and wash our eyelids free from makeup, paint, or any other dirt or oil from the day in order to keep seeing healthy. Getting checked by the eye specialist is very important to live a happy, and healthy lifestyle. If we do not have our health, what do we have?

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Spc. Colene Copeland with U.S. Army Garrison Bavaria. She is pre-med studying Forensic Medicine, Space and Aviation and Engineering. Spc. Copeland is working towards becoming an orthopedic trauma surgeon focused on the musculoskeletal and joint system. Follow along as she writes about interesting bones in both humans and animals, dives into space medicine, forensic science, engineering, healthcare and medical topics.