Having grey eyes is a unique and rare eye color that only around 2% of the global population possesses. While eye color is mainly determined by genetics, there are some factors that can cause a person’s eye color to change over time. In particular, age and certain medical conditions can lead to grey eyes in some individuals.
The Science Behind Eye Color
The color of your eyes depends on the amount and quality of melanin (pigment) in the iris. People with brown eyes have a lot of melanin in their irises, while people with blue eyes have much less melanin. Grey eyes sit in between blue and brown eyes in terms of melanin levels.
When you’re born, the melanin level in your iris is genetically determined and fixed. However, as you age, the melanin starts to deteriorate naturally. This causes the eye color to lighten gradually over time. Additionally, deposits build up in the stroma – the supporting tissue in the iris. These deposits blur and muddle the eye color, often turning blue eyes grey.
Greying of the Eyes with Age
Age-related loss of iris pigment is the most common cause of grey eyes in adults. Over time, the melanin levels deplete and the extracellular matrix and stroma of the iris become hazier. This natural ‘greying’ process is similar to hair turning grey or white with age.
Newborns often have blue or grey eyes initially. But as melanin production ramps up in infancy, the eyes usually darken to brown, hazel or green by around 1 year of age. Once adulthood is reached around 20 years old, the melanin starts to break down gradually. By the age of 50, significant greying of the eyes may become noticeable.
While this process is perfectly normal, the specific age timeline varies significantly between individuals. Some people may retain vibrant eye color well into old age, while others may see greying by 30-40 years old. Genetics, ethnicity, behaviors like smoking, and environmental factors all play a role.
By the age of 70-80, most Caucasian individuals have predominantly grey eyes, regardless of their original eye color. However, other ethnicities like Hispanics and Asians tend to retain more pigment as they age.
Medical Causes of Grey Eyes
Sometimes, grey eyes can be caused by medical conditions rather than simply age-related pigment loss. Two examples are light scattering disorders and pigment dispersion syndrome:
Light Scattering Disorders
Light scattering eye disorders are characterized by structural changes in the cornea and lens of the eye that results in blurry, greyish vision. Examples include corneal edema and cataracts. With corneal edema, the cornea swells due to eye injury or insufficient endothelial cell function. With cataracts, the lens becomes progressively cloudy.
Both conditions cause light entering the eye to scatter. This manifests as a greyish or foggy appearance to the iris, rather than true pigmentation changes. Treatment options include eye drops for mild edema, surgery for cataracts, and corneal transplant for severe edema cases.
Pigment Dispersion Syndrome
Pigment dispersion syndrome occurs when the iris pigment epithelium rubs against the lens or zonule fibers behind it. Over time, this friction causes pigment granules to break off and disperse into the interior chamber fluid. The liberated iris pigment can build up on other eye structures like the cornea, lens and trabecular meshwork.
This condition is characterized by mid-peripheral iris transillumination defects, where the iris color becomes greyish. Additional symptoms include eye pain, blurred vision, elevated eye pressure and glaucoma. Treatment depends on the symptoms but may involve medication, laser therapy or surgery.
Other Associated Factors
There are a number of other factors that may potentially impact eye color over time:
- Trauma or injury to the eye can damage the iris and reduce pigmentation.
- Some medications like chloroquine and phenothiazines are toxic to melanocytes and can lighten eye color with long-term use.
- Heterochromia may result in one eye becoming grey while the other retains its original color due to uneven pigment loss.
- Albinism prevents melanin synthesis altogether, leading to very light coloring including grey, blue or pink eyes.
- Malnutrition or deficiencies in minerals like copper, iron and zinc essential for melanin production may also play a role.
Lifestyle Factors and Eye Color
While you can’t change your genetics, certain lifestyle factors have been linked to eye color changes:
- Smoking tobacco seems to increase pigment loss and the risk for developing light-scattering eye disorders like cataracts.
- Exposure to UV light from the sun may destroy iris melanin over time, especially without adequate eye protection.
- High alcohol intake is toxic to melanocytes and associated with pigmentary changes.
- A healthy, balanced diet rich in bioavailable forms of minerals like zinc and copper promotes melanin synthesis.
- Stress and fatigue may potentially impact melanocyte function and accelerate pigment loss.
Making healthy lifestyle choices is advised to support eye health as you age, regardless of your eye color.
Conclusion
While eye color is largely determined by genetics, several factors can lead to the greying of eyes over time. The most common cause is simple age-related breakdown of iris pigment, but medical conditions like light scattering disorders and pigment dispersion syndrome are sometimes to blame. Other associated factors range from ocular trauma to poor nutrition. Making positive lifestyle choices may help mitigate pigment loss.
So if you notice your eye color becoming progressively greyer, don’t panic. Some pigment loss is normal with aging. But significant changes in eye color or vision should be evaluated by an eye doctor, especially if other symptoms are present, to check for any underlying conditions.
Summary of Main Causes
| Cause | Explanation |
|---|---|
| Aging | Natural breakdown of iris pigment over time |
| Light scattering disorders | Structural changes in the eye that disperse light and alter eye color |
| Pigment dispersion syndrome | Iris pigment rubs off on other eye structures, causing color change |
| Ocular trauma | Injury damages iris and reduces pigmentation |
| Medications | Some drugs are toxic to melanocytes |
| Nutritional deficiencies | Lack of minerals needed to produce melanin pigment |
