Ask the doctors
Q: How common is it to have eyes that change colour? I have noticed lately that my green eyes are turning brown.
A: Iris colour is very much a function of the density and distribution of the iris pigment (melanin) in the iris pigment epithelium. This is genetically determined. For lighter-coloured eyes, the hue may vary according to the ambient lighting condition. The colour of the eyes could change during puberty, early childhood, in certain eye diseases and after major ocular trauma.
Studies on Caucasian twins, both fraternal and identical, have shown that eye colour over time can change, and major loss of melanin in the iris may also be genetically determined. Most eye-colour changes have been observed or reported in white people with hazel eyes.
If you have any visual symptoms associated with the colour change, you may want to have your eyes properly examined.
Dr Kenneth Ng is a specialist in Ophthalmology at the Eye Institute of Hong Kong