Why do Eye Color Changes Occur?

In Pediatrics, it is common for parents to ask the specialist about the color of their baby’s eyes, just after birth. At that time you should respond with caution, since the color of your baby’s eyes is not yet final …

Anatomy and development of eye color

The colored area of the eyes corresponds to the iris , which is a muscular ring that surrounds the pupil and whose function is to regulate the amount of light that passes through it and reaches the retina, thus participating in the phenomenon of vision.

The color of the iris is defined by pigments such as melanin that is secreted by specific cells present in our body called ‘melanocytes’. This pigment will also define the coloring of the skin and hair of the person in question:

  • Brown or black color: it occurs when there is a greater amount of melanin deposited in the stroma of the iris.
  • Blue color : occurs when there is an absence or minimal presence of melanin
  • Green, honey or hazelnut color : when there is a partial deposit of melanin .

At the time of birth, the eye is still immature and in most cases the pigmentation of the iris is still little or no. That is why its layers are seen reflected, through the transparent media of the eye, as an indefinite grayish and / or bluish coloration, difficult to describe. That is why babies do not yet have a defined eye color .

How do you define eye color?

It is decided by the genes included in the DNA of the cells of the individual in question. Of each gene in our human genome , we receive one copy from the paternal parent and another from the maternal one.

Many times we have heard that if one of the parents has dark eyes , it is most likely that the offspring also has dark eyes and is unlikely to have blue eyes. Or that if both parents have light eyes , the children will have light eyes. Both statements can be considered true on the grounds of probability, but should be used for guidance only, since the color of a baby’s eyes is not defined only by a simple pattern of crossing between the parents.

Like everything in medicine, the inheritance of eye color is more complex than we suspected. Different scientific studies, carried out over the last decades, have shown that there are multiple genes that influence the tone of our iris ; eye color is what we would define as a “polygenic trait”.

It depends on genes such as HERC2 and OCA2 , both located on chromosome 15 , among various other genetic sequences (chromosomes 19, 14, 11, etc.). In other words, although we can make a first prediction of children’s eye color by their relatives, the different genetic combinations can give unexpected and surprising results.

Diseases that cause eye color abnormalities

Oculocutaneous albinism

The albinism is an inherited disease in which there is a congenital absence (already present at the time of birth) of eye pigments, as well as the skin and hair. Different degrees of severity of the disease differ.

Heterochromia

Color asymmetry between both eyes, that is, the iris of each eye of a different color , which can be partial or sectorial (only one part of the eye) or complete (for example, one eye is totally green and the other is totally blue). The case of congenital heterochromia (present already at birth) is not usually a worrying disease or condition, but an association with certain syndromes must be ruled out at first, such as: von Recklinghausen disease, Waanderburg syndrome or Sturge-Weber syndrome.

Aniridia

Bilateral absence of the ocular iris. Rare genetic condition. You can see the circular area that would correspond to the iris, completely black in color.

What you should know:

  • At the time of birth, the eye is still immature and in most cases the pigmentation of the iris is still little or no.
  • With the passage of time, according to genetic guidelines, the pigment will gradually deposit in the stroma of the iris until the final color of the eye is configured.
  • Later, specific disease situations (tumors, ocular bleeding, glaucoma, diabetes mellitus, deposits, etc.) can cause changes in the total or partial coloration of the eyes, as well as a spontaneous loss of ocular pigment in the final stages of life.

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