Iris of the eye. It is the colored part of the eye. It also refers to the iris as a colored membrane. At its center is the pupil, black in color; the white area around it is called the sclera. The iris regulates the entry of light into the eye like a diaphragm from a photo camera. The organ is made up of muscle tissue and pigment. If the orbicularis iris muscles contract, the pupil shrinks and less light enters the eye. If the orbicular muscles relax, the pupil dilates again, allowing more light to pass through to the retina. The pigment determines the color of the eyes. The more pigment in the iris, the darker the eyes will be.
Summary
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- 1 Iris diseases
- 2 Function
- 3 Importance
- 4 Main pathologies of the iris
- 5 Sources
Iris diseases
- Coloboma of the iris:It is one of the most frequent congenital malformations of the iris. It is characterized by a cleft due to the lack of development of the iris (or some other part of the eye (lens, retina, choroid or optic nerve). It can be unilateral or bilateral. Vision will be more or less altered, depending on which area be the anomaly.
- Aniridia:It is a complex condition of birth, rare, with an underdevelopment of the iris. It occurs during pregnancy due to a genetic defect. Hereditary and congenital malformation, which is usually bilateral and hereditary. It is a partial or total absence of the iris, or pigmented tissue behind the cornea. It causes decreased visual acuity and can be associated with glaucoma and corneal and lens opacities. Symptoms include poor outdoor vision, photophobia, and poor contrast sensitivity. Vision can be improved with sunglasses, optical aids and soft lighting.
Function
The main function of the iris is to control, through the pupil, the amount of light that enters the eye in order to facilitate the focusing of objects on the retina. But how does the iris manage to control the amount of light it lets into the eye? Basically because of its ability to contract and expand. The process is as follows: The pupil and the iris muscles (called orbicularis muscles) contract or shrink when we are in a bright environment, allowing less light to pass through to the retina. On the contrary, when there is little light the pupil dilates and the muscles relax, allowing more light to pass into the retina.
A secondary function of the iris is to give each person the characteristic color of our eyes. This tonality will depend on 2 factors:
- The thickness of the pigmentation sheets.
- Melanin concentration.
The tonality of the eyes will be darker if the thickness of the fan of sheets and the level of melanin is greater. On the contrary: if said thickness and level of melanin is smaller, the eyes will be lighter.
Importance
The iris is more important than many people think, since a deficiency of the iris can affect (even seriously) vision. The problem is that a malfunction of the iris can cause poor focus on objects in the retina, as it is not possible to optimally regulate the amount of light that enters the interior of the eye. It can also happen that, due to affectation of the iris, some holes are produced in it that cause some secondary light rays to impact the retina, producing double images or ghost images.
Main pathologies of the iris
- Ocularalbinism : Albinism is a genetic disorder that causes abnormal pigmentation. When it affects the eyes it is called ocular albinism and it is characterized by the fact that the iris appears transparent or white because the light passes directly to the retina.
This disorder can cause strabismus, sensitivity to light, and even significant loss of visual acuity.
- Uveitis:Uveitis is an inflammation of the [uvea] that is made up of the iris, ciliary body, and choroid. When the infection affects the iris, it can become inflamed, producing various symptoms such as: redness, itching and eye pain, sensitivity to light or blurred vision.
Uveitis is usually resolved with cortisone ointments, which are usually highly effective. But like everything related to our eyes, the diagnosis, choice and prescription of the most appropriate treatment corresponds to an ophthalmology specialist.
