Change in Baby’s Eye Color - Reasons and Probabilities

Introduction:

Parents may notice that the color of the eyes in babies is not the same as when they were born. This is completely normal, and there is nothing to worry about. The color change usually happens between 6 to 9 months and continues till three years of age. Sometimes, it happens even when the child enters adulthood. Melanin is a pigment responsible for eye color, and any change in the quantity and quality of this pigment causes the baby's eye color to change.

How Is a Baby’s Eye Color Determined?

A Baby’s eye color is inherited (obtained from parents) and unique, like fingerprints. The following factors determine the baby’s eye color:

• Genetics: It is believed that 16 genes are responsible for deciding the baby's eye color. Two significant genes involved are HERC2 and OCA2, located on chromosome 15. The pigment which influences eye color, called melanin, is produced by cells called melanocytes and stored in structures called melanosomes. The quantity and quality of melanin are regulated by a protein called ‘P protein’ that is produced from the OCA2 gene and directs the development of melanosomes. The amount of P protein released from the OCA2 gene is directly proportional to the amount of melanin and hence, the eye color.

In addition, the OCA2 gene is controlled by a DNA segment on the HERC2 gene, turning it on and off when needed. The following are the minor genes that affect eye color in combination with the significant genes.

1. ASIP (Agouti Signaling Protein)

2. IRF4 (Interferon Regulatory Factor 4)

3. SLC24A4 gene

4. SLC24A5 gene

5. SLC45A2

6. TPCN2 (Two Pore Segment Channel 2)

7. TYR gene

8. TYRP1 gene

• Melanin: The black part of the eye called the pupil screens the amount of light entering the eye. The muscular structure around the pupil is called the iris, which has two layers: the front (stroma) and the back (pigment epithelium). The activity of the melanocytes determines melanin production. The following are the eye colors based on the melanin level.

1. Brown Eyes: When both the layers of the iris are active, absorption of light increases, hence the appearance of brown eyes. Brown eyes are common in the majority of the population. If there is more activity, the eyes appear black.

2. Blue or Gray Eyes: 25 % of the population has blue or gray eyes. This is because the front layer of the iris reflects off the light as there is no pigment.

3. Green or Hazel Eyes: When there is a low melanin content in either of the two layers of the iris, blue light reflects the pigment giving a green color to the eyes. Less than 10 % of the population have green eyes, and about 18 % have hazel eyes.

The most dominant gene of the parent will determine the eye color, but it is subject to vary.

What Are the Other Reasons That Determine the Eye Color of the Baby?

The other reasons that determine the baby’s eye color are:

• Region or Ethnicity: Black, Asian, or Hispanic parents have kids whose eyes are usually brown. Certain scientists believe that based on climatic variations, people in Northern Europe have lighter eyes than those in the South.

• Health Conditions: Certain health conditions can affect eye color, such as:

1. Ocular Albinism: There is a very low level of pigmentation in the iris, which causes light eyes, and vision might also be affected.

2. Oculocutaneous Albinism: There is an overall decrease in the pigmentation of skin, hair, and eyes; hence, these individuals have very light-colored skin, hair, and eyes. This is known as albinism.

3. Heterochromia: The eye color can be different in the same individual. The possible reasons can be genetic changes, injury to the eye, disturbance during eye development, or due to another disease. If there is a difference in the color of each eye (heterochromia) as early as six months of age, it is recommended to consult a pediatrician.

4. Waardenburg Syndrome: Waardenburg syndrome is a rare genetic condition in which the baby’s skin, hair, and eye color are affected. The color can differ in both eyes.

5. Horner’s Syndrome: Horner's syndrome is a disturbance in the nerve track from the brain to one side of the eye and face that can cause one eye to be lighter than the other.

What Is the Guide to the Change in the Baby’s Eye Color?

The following changes in baby's eye color concerning their age are just a guide; they can differ with each baby.

• 6 to 9 months: This is when changes in eye color might begin to occur, and the process is gradual. Eyes start to darken with the production of melanin.

• 12 months: By this time, the eyes have gained their final color. However, the change can progress up to 3 or 6 years and rarely into adulthood.

What Are the Probabilities of Getting a Particular Eye Color?

The following are the probabilities of inheriting a particular eye color:

• Both Are Blue-Eyed Parents: High probability of the baby having blue eyes, but it is not assured.

• Both Are Brown-Eyed Parents: Babies will have brown eyes, but if either or both parents have family members with blue or lighter eyes, there is a chance of the baby inheriting an eye color besides brown.

• One Blue-Eyed Parent And One Brown-Eyed Parent:There is a 50-50 chance of the baby getting blue eyes in this condition.

• If One Or Both Parents Have Green Or Hazel Eyes: It is possible that the baby can have green or hazel eyes, but it is not assured.

The eye color tends to change from light to dark and not vice-versa. Therefore, it is not definite that the baby will inherit the same color as the parents. In addition, kids with light eyes have less pigmentation in the iris; hence, the eyes cannot cut off the extra light entering the eyes. So, these children may be photophobic (sensitive to light), and parents should not allow the kids out in the sunlight for long.

Conclusion:

A baby's growth during the first year is the most interesting phase, wherein a majority of changes occur. Besides genetics, another logical explanation for the change in a baby's eye color is the increase in melanin pigmentation after birth as they get exposed to sunlight. The amount of change is, however, controlled by genetic factors. For example, babies born dark might have relatively high levels of melanin and dark eyes. Whatever the reason, a change in eye color is a part of the developmental process in babies and should not be a matter of concern for parents.