Archive for November, 2010

What is Cornea?

November 29, 2010 Leave a comment

The cornea can be said to be a very important part of the eye. It is located in the front portion of the eye and is transparent. The cornea provides a wrap for the anterior camber, iris and the pupil. It works as a protective shield and does not let germs and other harmful particles affect the eyes. It also controls the penetration of light and helps in focusing. It along with the lens is responsible for refracting light and helps the eye focus. The Cornea is accountable for most of the (approximately 2/3rds) optical power of the eye. The cornea is very sensitive because of the unmyelinated nerve ending. It is sensitive not only to touch but also to chemicals and temperature. The reflex action can be seen when it is touched as it involuntarily causes the eyelid to close. It is probably the most sensitive tissue in the human body. A very interesting fact about the cornea is the absence of blood vessels. Because it is absolutely essential that the cornea remains transparent, the blood vessels are absent. Another interesting fact is that the cornea has 5 layers. Let us briefly look at the 5 layers of the cornea:

1. Corneal Epithelium: is a tissue layer which is multicellular. They grow rapidly and the cells are easily regenerated. This layer stays moist due to tears.
2.   Bowman’s Layer: is a very strong layer in the cornea. It provides a protection to the corneal stroma. The layer is 8-14 microns in thickness.
3.   Corneal Stroma: this is the middle layer of the cornea. This is probably the thickest part of the cornea as 90% of the thickness is that of the stroma. It is made up of type 1 collagen fibrils having close to 200 layers.
4.   Descemet’s Membrane: is a very thin layer that functions as a customized base membrane of the corneal endothelium.
5.  Corneal Endothelium: is the layer which regulates the flow of fluid and solute between 2 compartments i.e. the corneal stroma and the aqueous.

In refractive surgeries, the corneal shape is changed due to which the person can avoid using corrective lenses. Most advanced techniques use lasers which help in reshaping the cornea.


Total Eye Care

November 12, 2010 Leave a comment

Structure of the Eye

All about eyesight

The 20/20, is a term one would have heard so many times when it comes to discussing eyesight. What exactly is a 20/20 vision? The clarity of one’s vision is usually tested at a primary level using a Snellen eye chart. The standard method of reading the chart is from a distance of 20 feet. A 20/20 vision indicates that the person can read the chart from a distance of 20 feet and this is what is visible to a person with normal Eye Sight from 20 feet away. The same can also be termed as 6/6 vision when the distance is calculated in meters. Though 20/20 is labeled as the perfect vision one can have eyesight which is above that. The maximum clarity till recently was thought to be vision which is 20/10 but most recent studies have shown eyesight better than 20/8. There are birds such as hawks and owls which have visions that are much sharper than humans. Birds like hawks are said to have a vision which is 20/2.

There are many who do not have the so called perfect 20/20 vision which is considered most favorable by physicians. People suffer from many an eye problem like near-sightedness, far sightedness and complications such as astigmatism. 20/20 cannot be said to be the perfect eyesight but just a measure that is considered normal. It actually is only a way of denoting the vision acuity from a particular distance. It is only a basic measure of vision. But there are various other factors that affect the visual ability of a person like the side or peripheral vision, perception of depth, coordination of the eyes, the ability to focus and the color vision. All these factors together contribute to the actual visual ability of an individual.

Persons suffering from many vision problems can get the same corrected by the use of glasses or contact lenses. Some people also suffer from eye diseases which can be treated with ocular medication. A comprehensive eye examination can determine the exact problem and the necessary treatment option can be adopted. A very popular way of treating many an eye problem today is the Lasik surgery. The laser surgery is very effective and has proved beneficial to many and a large number of those who suffered from vision complications have been blessed with a 20/20 vision and Lasik surgery has proved to be beneficial and a boon to many.

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