Iris - Contributes to the Eye Color
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Iris : Contributes to the Eye Color

Dr.Surya Rao Poodipeddi profile Authored by Dr.Surya Rao Poodipeddi on 17 Apr 2014 - 10:35.

The iris present in each eye is always symmetrical and is a colored muscle that has a unique feature presenting itself in different colors in different people giving the eye a distinct color.

The opening in the center of the iris is called pupil which becomes smaller and bigger as per demands for the entry of light similar to the aperture in a camera.

There are two types of pigments responsible to give the iris its distinctive color. Eumelanin is the pigment responsible for the brown color of the iris whereas Pheomelanin is the pigment that gives the iris blue or green color. It therefore follows that some people have brown colored iris where as some have green or blue colored iris depending on the pigment involved and predetermined right from conception.

One of the columns in any application form for passport or other documents requires mention of the color of the eye. In other words, the color of the eye means the color of the iris like brown, blue or green.

Iris Structure: The iris has two types of muscle fibers namely circular and radial responsible to make the size of the pupil big or small depending on the amount of light needed. For example during bright sunny morning the amount of light needed is less and when it is dark more light is required to pass through the pupil. The pupil changes its size as per the requirements of the light and this is where the muscle fibers in the iris get involved.

The Iris is one of the three components in the formation of the uveal tract the other two being the ciliary body and the choroid. The iris is the colored ring around the black pupil. The ciliary body is a set of muscles responsible to make the lens thicker when near objects need to be focused and thinner when far objects need to be focused. The choroid is the inner lining of the eye that extends from the edge of the ciliary muscles to the optic nerve far behind the eye.

The entire uveal tract or any of its parts can get inflamed due to any cause. Usually infections lead to inflammation of the uveal tract. Inflammation of the iris alone is called iritis. Inflammation of the choroid is known as choroiditis. Inflammation of the entire uveal tract is known as uveitis,

Besides infections, inflammation of the uveal tract may be due to any cause with in the eye or any condition affecting the whole body.

Some of the other common causes for uveitis are:

  • Syphilis
  • Tuberculosis
  • Sympathetic Optholmits (a condition where the other eye is affected when one eye is inflamed)
  • Toxoplasmosis (a condition which results in total blindness)
  • Juvenile Rheumatoid Arthritis
  • Some types of cancer.

Whatever be the cause for uveitis it is important to note that any delay or negligence in initiating treatment might lead to long term complications like glaucoma, cataract or even detachment of the retina.

The main symptoms of uveitis include haziness in vision and experiencing floating black spots, severe pain, redness in the conjunctiva (white of the eye) and sensitivity to light which are more common in iritis.

Treatment must start early to avoid serious complications and includes use of drugs to dilate the pupils and corticosteroids to reduce inflammatory process. Appropriate antibiotics are a must to take care of bacterial infections.

In rare cases there may be absence of iris known as Anairidia. (Born without an iris) The iris may get involved in piercing injuries damaging the iris. In such cases implantation of artificial iris may improve patient’s vision and appearance. Lot of research work is going on to design improved artificial iris. Few cases of successful implantation of artificial iris have been reported in Canada, Europe, Middle East and Asia.


*Disclaimer: This is not medical advice. The content is for educational purposes only. Please contact your doctor for any health care issues.