Submission Three
Picture
(Photo taken by Tasmin)
Picture
(Photo taken by Tasmin)

We like to look at each others eyes and discuss the colours, how pretty or unique they look, but I want to find out what this coloured part of an eye is called, what it is for and what different colours there is.

Picture
(Photo taken by Tasmin)

The coloured part of the eyes is called the Iris. It is a ring of muscle fibers which is located behind the cornea and in front of the lens. The iris is responsible for controlling the size of our pupils, determining how much light reaches the retina. The amount of light that can enter the eye is controlled by the muscles that are attached to the iris. These muscles contract or expand, making your pupil smaller or larger, in response to the brightness of surrounding light.  The larger the pupil, the more light can enter, the iris is there to help protect the sensitive retina.


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The colour varies for everyone, there is: Amber, Blue, Brown, Gray, Green, Hazel, Red and Violet. Eye colour is genetically associated with certain skin tones and hair colour. There are 3 main elements within the iris which contribute to its colour: The melanin content of the iris pigment epithelium, which is a layer at the back of the iris. The melanin content within the iris stroma, which in dark eyes contain pigment granules, but blue eyes are unpigmented. And the cellular density of the iris stroma.


Picture
(Photo taken By Tasmin)

This is an example of complete Heterochromia; this is when one eye is a completely different colour to the other. Even though this is not so common in humans, complete Heterochromia is more commonly seen in other species; this is where it is mostly involving one blue eye. The species include cats, dogs and horses. The so called odd-eyed-cats are mainly white, with one normal eye (orange, copper, yellow, green) and the other bright blue.


From my findings I have found out the colourful part of our eyes is called an Iris, and this plays an important role to protect our retina, determining how much light to let in. Everyone has different coloured eyes and this is based on melanin levels, the lighter your iris colour the less melanin. I have found this investigation very interesting and I have learnt alot! I am very fascinated and want to learn more.