At the age of 5, you look at the mirror and you saw that brown-eye of yours and you conclude that your eye color is brown even 20 years after because while the body can change, the eye doesn't change so you thought, but that's not true. There are a lot of things that can lead to the change in the color of eyes and those are the things we will be diving into today. What can make those baby-blue eyes not blue anymore but before I tell you all those interesting stuffs, let's explain the basics.
The iris is responsible for the inflow of light into the eyes as it contains the muscles that opens and closes the pupils and in doing so, it regulates how much light gets into the eyes but asides that, they give the eyes that interesting color as a result of its cellular makeup, giving it different spectacular colors in people. These are thanks to the cells known as melanocytes, the same color pigment in the body and hair.
Melanin absorb light and with this, the more the melanin, the higher ability to absorb light which gives the more darker skin. With this, it means that in brown colored eye, there is a higher amount of melanin and so with lesser melanin means eyeballs that can reflect short wavelength of light off collagen fibers. This is why when other people look at those light melanin-eyes, their eyes pick up the reflected light helping us to see the color of other people's eye.
Melanin comes in two form and you as you would expect, it has to do with color with one being Eumelanin (dark brown or black), and Pheomelanin (light brown, red, or yellow) Different combination of Pheomelanin can give eye their color, but then not all eye color is a result of Melanin like in the case of albinism where there is little to zero melanin, then it is the blood vessels in the retina that reflects back light in the eye. So, now that we have a good background, let's discuss the different causes for color changes in our eye.
First, babies have everything in infancy ready for change, from developed brain, bones, and eyes. Their eyes are get darker as they grow older and this is because either the melanocyte in the eyes are yet to be developed completely or yet to move completely into place. Over their years growing, the iris is populated by the cells which then gives the pigment to the eyes causing the eye to change color around about 6 years old and adulthood.
Aging is another reason that can cause the eye to become darker or Haylike as the pigment becomes darker but this an also be the cause of an underlying condition associated with old age, so it is advisable to take them to the hospital to get their eye checked especially when they have hue on their iris. Talking about eye conditions, there are conditions that can lead to loss of pigment in the eye thereby causing lighter eye or change the color of the eye and a simple example of those condition is Horner syndrome which as a result of damage to certain nerves in the head and neck leading to a lot of symptoms including a change in the color of the eyes making the eye color lighter.
Kayser-fleischer ring is another reason why a person can see changes in the color of their eyes. This happens when there are little rings formed around the iris which happens as a result of excess copper in the cornea on top of the iris. This is common with conditions like Wilson's disease which is a genetic disorder causing an error in copper metabolism in the body or caused by liver disease but once the underlying condition are treated, the ring should disappear.
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Another reason for a change in eye color is cancer such as Iris Melanoma. While this is not common it happens and this usually present as a dark brownish spots on the eyes which can also lead to seeing floaters while changing the shapes of the pupils. Another cancer that can cause changes in the color of eye is Retinoblastoma which is found in children. The treatment is what is usually responsible for the change in the color of the eyes as chemotherapy drugs are injected into the vitreous humor of the eyes.
While conditions can cause color change in eyes, treatments can also cause it. Protaglandin is on treatment for Acute Angle-Closure Glaucoma which is part of a group of conditions as a result of pressure on the eyes leading to the damage of the optic nerve over time. The treatment is known to darken people's eye while it is doing the good job of removing the pressure on the eye.
We can tell now that there are many reasons why a lot of people can have color changes and while some of them are beautiful if natural, a few needs urgent medical attention so the eyes and eye sight isn't lost.
Read More
https://www.aao.org/eye-health/tips-prevention/why-are-my-eyes-changing-color
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8956647/
https://www.cancerresearchuk.org/about-cancer/melanoma/about
https://www.ncbi.nlm.nih.gov/books/NBK554370/
https://www.nature.com/articles/eye2011228
https://pubmed.ncbi.nlm.nih.gov/15288975/
https://jamanetwork.com/journals/jamaophthalmology/article-abstract/641593
https://www.ncbi.nlm.nih.gov/books/NBK532252/
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3996377/
https://jamanetwork.com/journals/jamaophthalmology/article-abstract/641593
https://www.nhs.uk/conditions/albinism/
https://www.ncbi.nlm.nih.gov/books/NBK441887/