Five Types of Astigmatism and What They Do To Your Vision
What is Astigmatism
To understand Astigmatism it is first important to understand what the normal (non-astigmatic) eye, called the emmetropic eye looks like and how it works to help you see clearly. When light enters the eye through the dark black opening of the eye called the pupil, light rays are actually bent by two powerful structures of the eye. The first is the clear outer covering of the eye called the Cornea, as light rays pass further into the eye they are further bent by the interoccular lens so that all the light rays come together (converge) to form a perfect focal point on the retina.
Astigmatism is noted for being the most common refractive error when it comes to problems with vision and affects nearly two-thirds of the population. Astigmatism is a condition where the cornea is not shaped perfectly spherical. When the Cornea is aspherical in shape as occurs in those with astigmatism, light rays are converged to more than one focal point. Because light rays form multiple focal points this creates unclear vision and can effect vision in both the distance and up close. There are five different types of astigmatism, what are the differences, and how is astigmatism treated?
How Astigmatism Can Be Treated?
The effects of astigmatism can be treated with Prescription Eye Glasses, Prescription Contact Lenses or via Lasik. For eye glasses your eye doctor will prescribe a sphero-cylinder spectacle lens rx. Contact lenses of various materials can be used based on your doctors recommendation including soft disposable contact lenses. Or Lasik surgery may also be performed. In cases of astigmatism, the surgeon will use a laser to reshape the cornea so it can focus light rays to one focal point exactly on the retina. Consult your eye doctor for more information on all of these options to see which ones are right for you if you have an astigmatism.
The Five Different Types of Astigmatism
With all types of astigmatism light rays come together to form not one but two focal points. The mere fact that there are two focal points formed, instead of just one (in the normal seeing eye) creates vision problems.
The first type of astigmatism is called Simple Myopic Astigmatism, where light comes to two focal points: one before the retina, and one on the retina.
The second type is called Simple Hyperopic Astigmatism, where light comes to two focal points: one on the retina and another focus point that would be a virtual point behind the retina.
The third type is called Compound Myopic Astigmatism where light comes to two focal points, both of which are before the retina but at two different locations before the retina.
As you might have imagined, the fourth type is called Compound Hyperopic Astigmatism where light comes to focal points both of which would be in a virtual location behind the retina but at different virtual locations behind the retina.
Finally, the fifth type is called Mixed Astigmatism where light rays come to two focal points, one of which is before the retina and the other of which is behind the retina
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