One of the questions that I most often get from parents during their child’s first eye exam is “what colour would you call my child’s eyes?” As colour is a perception and unique to the perceiver, I usually diplomatically ask what the parent thinks first about their child’s eye colour.
The iris is the coloured part of our eyes. The iris acts as a filter to reduce the intensity of light that enters our eyes; it controls the pupil size and the amount of light entering the retina.
There is a wide range of iris colouring. In some cases there is a blend of colouring in the iris, and the colour can vary in a sector of the iris due to an iris nevus (freckle). The iris will sometimes appear to be different colours depending on the surrounding environment. It is a fallacy that the eye colour changes depending on the mood of the person but it can be perceived to be different depending on what colour clothing the person is wearing as well with varying lighting conditions.
Viewing the iris (plural irides) under the biomicroscope is an awesome experience, particularly the first time I viewed one in my training. The iris has architecture of crypts and valleys with coloured strands emanating throughout. The depth of colour can be quite breath taking. The ever changing pupil can give the iris the look and feel of something breathing.
At birth, many children are born with blue eyes that can darken for two years or more. This is because the melanocytes are immature at birth and develop until the iris takes the colour it will eventually have in adulthood. Brown eyes are genetically dominant. That means to have a blue eyed baby, both parents must be blue eyed or carry the recessive gene for blue eyes while being brown eyed themselves.
My wife and I have three children, all with different coloured irides. My eldest has brown eyes, our second has green eyes and the youngest child has one dark brown iris and one green coloured iris. He has a rare condition known as ocular melanocytosis. This condition is characterized by over pigmentation in the darker coloured eye. At first we thought the curious eye was the lighter pigmented eye but some other signs of hyper pigmentation at the sclera (white of the eye) confirmed the ocular melanocytosis diagnosis in the darker eye. Other than being very rare and curious in pictures, ocular melanocytosis can lead to glaucoma in some cases. In these cases the hyperpigmentation leads to blocking of the drainage of the eye’s fluids and increased fluid pressure and damage to the optic nerve (glaucoma).
Iridology is the alternative medicine technique whose proponents believe that patterns, colours and other characteristics of the iris can be examined to determine information about a patient’s systemic health. Iridology is not supported by most eye care professionals and has no support in the medical journals.
Next time somebody asks to look deep into your eyes, you will know more about the iris!