How Are Eye Colours Determined, and Can They Change?

The personality of children, along with several of their physical features, depend on the genetic factors that each parent contributes to them. Often, eye colour is among the major genetic traits that attract the parents' attention as the child grows.  

The inheritance of our eye colour is much more complex than we think because multiple genes are involved. While children’s eye colours can be predicted by the eye colours of their parents and other family members (relatives), variations in genetic material can produce surprising results in some cases.

What are eye colour percentages around the world?

According to recent statistics, a high percentage of the world’s population (70% to 79%) has brown eyes, with blue coming in a distant second place (8% to 10%), and the population with green eyes stands at third place (2%). 86% of the population in Scotland and Ireland have one of these colours (blue and green). However, the Albinos (1%) have red eyes due to the lack of pigmentation in their eyes that exposes the underlying blood vessels. 3% of the world population has grey eyes, 5% have amber eyes, 5% have hazel eyes, and some have two distinct colours in both eyes. This condition is called heterochromia.

How is eye colour determined?

Scientists previously believed that eye colour is determined by two eye colour genes (one from each parent). This was due to brown being dominant over blue (a blue-eyed individual would have two blue eye genes, and two blue-eyed individuals or parents could not have a brown-eyed child).

However, that does not always appear to be the case. The eye colour is determined by various genes that control the production of melanin in the iris. Melanin absorbs light, and when an object absorbs light, it appears dark. However, light reflects from the object when it doesn’t absorb light, and the object becomes the colour of the light it reflects. Hence, dark eyes have a lot of melanin, whereas light eyes have very little melanin in them.

Brown eyes have more melanin, followed by hazel eyes, which have less melanin than brown eyes but more melanin than green ones. Blue eyes have the least quantities of melanin. As a result, brown eyes absorb the highest light quantities and appear darker, whereas blue ones reflect the lowest light amounts and appear lighter.

Can eye colour change?

Your eye colour can alter naturally due to the contraction and expansion of the iris in the presence of light. This also happens when the iris starts to age. While this alteration is a natural phenomenon, and few cosmetic accessories can allow for temporary changes, there is no safe way to permanently change the colour of the eyes.

Furthermore, there are two artificial ways to change the colour of the eyes, but as mentioned before, both options may have risks. These methods are described below:

• Contact lenses: You can choose to enhance or completely change your eye colour. These lenses come in various colours and can correct your vision if you have vision problems and do not wish to wear glasses.
• Iris implant: This is a surgical procedure that was originally developed to treat eye injuries and other eye conditions. This iris implant has been used by many to change their eye colour permanently.

Health problems that show up in eye colour

Some medical conditions impact your eye colour. However, instead of permanently altering the iris colour, they generally affect the cornea or whites of your eye. Some such conditions are described as follows:

• Anisocoria: In this condition, one of the pupils becomes larger than the other. Some are born with this condition, and some may suffer from it due to brain injury, eye trauma, or stroke. You should get immediate medical help if the condition occurs suddenly.  

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• Albinism: Here, the eyes do not produce sufficient melanin. If it’s mild, the person may usually have violet or light blue eyes. However, if it is severe, then that person may have little or no melanin.
• Hyphema: Under this condition, blood can be found inside the eye. This can happen due to an injury or following surgery.
• Arcus senilis: In this condition, the cholesterol builds up and leads to the formation of a hazy blue or white ring around the cornea. However, this is very common and harmless as you age.

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• Hepatitis and other liver diseases: When the liver gets damaged or inflamed, it cannot remove bilirubin. This starts to build up in the blood and makes the whites of the eyes and skin yellow.

If you face symptoms of any of the conditions mentioned above or wish to avail of the most effective eye care treatments from one of the best eye hospitals in Kolkata, schedule an appointment at Netralayam, the superspeciality eye care center. We comprise the most sophisticated medical infrastructure and a skilled team of eye specialists who can successfully treat most eye conditions.