Eye colour is determined by two main factors; the amount of pigmentation found in the iris and the way light is scattered as it hits the top layer of the iris. The iris is a thin circular membrane behind the cornea. It is responsible for controlling the size of the pupil and controls the amount of light that enters the eye.
As the pupil changes, compresses and dilates, the pigments in the iris may compress or spread apart causing the eye colour to change.
The iris of the human eye is very unique and a person’s eye colour is influenced by their genetics. The genetic information you receive from your parents affects the pigmentation, and the colour of your eyes is also determined by the concentration of melanin. People with brown eyes have a large concentration of pigment whereas people with blue eyes have a lower concentration of pigment. The more melanin the darker the eye colour and the distribution of pigmentation in the iris affects the way light is scattered and passes through the eyes.
When a child is born, melanocytes begin to produce melanin, this is a reason why some babies eye colour changes over time. As melanin production does not start at birth some babies’ eyes may appear blue but gradually change as they develop. Some people have varied concentrations of melanin, however, on a global basis people commonly have brown eyes. Around 80% of people have brown eyes, while only 8-10% of people have blue eyes. Green eyes are the rarest eye colour.
Eye colour may also change with age or as a result of certain eye conditions. Overexposure to the sun can make your eyes darker over time. It is important to keep protected from the sun’s UV rays. If you notice any sudden changes in your eyes, it is advisable to schedule an appointment with an eye doctor. It is important to take good care of your eyes and schedule regular eye exams.
Author: Samer Hamada is a distinguished consultant ophthalmologist and cornea surgeon performing eye surgeries at his practice, Eye Clinic London. With nearly two decades’ experience, Mr. Hamada is recognised as a leading expert in the field of cataract, refractive lens exchange (RLE) and corneal surgeries.
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