What is astigmatism? What part of the eye does astigmatism affect?
Astigmatism is a refractive error and very common imperfection of the eye where either the surface of the eye (the cornea) or the lens inside of the eye have unaligned curves. When the cornea or the lens is no longer spherical and have mismatched curves, light isn’t bent differently through the different curves. This causes the light to focus at different points where different images form resulting in blurred vision. Corneal astigmatism refers to the case where the abnormal curves occur at the cornea while lenticular astigmatism refers to the lens having abnormal curves. It is common for astigmatism to be associated with nearsightedness (myopia) and farsightedness (hyperopia). Nearsightedness refers to the cornea being curved too much which causes light to to be focused in front of the retina making objects that are far away blurry. Farsightedness refers to the cornea being curved too little which causes light to to be focused in the behind the retina making objects up close blurry. This can also make streetlights appear to have streaks or bloom surrounding them.
What are the symptoms?
There are many symptoms that are associated with having an astigmatism. Blurred vision is the most common symptom but other symptoms of astigmatism can include headaches, fatigue, straining of the eyes, squinting to see clearly, and seeing glares or halos around lights. Children may not realize that their vision is blurry, therefore it is recommended that school aged children have an annual eye exam to monitor vision and get screened for any other abnormalities. Both types of astigmatism contribute to blurred vision. Schedule your visit with an optometrist if you are experiencing any of these symptoms.
How are astigmatisms diagnosed?
Astigmatism can be diagnosed using a few different tests that your optometrist will perform on your eyes during your eye exam. One of these tests, keratometry, measures the curvature of the cornea. Most patients recognize this as the first test at an eye care visit where you look into a machine with a farm house that becomes blurred then clear. The machine shines a light into the eyes and measures how it changes as the light bounces off the back of the eye (the retina). Another device that allows an optometrist to make a diagnosis of an astigmatism is called a phoropter. This device resembles a large pair of binoculars that an optometrist will use and adjust your prescription as you tell them which letters you can see clearly. An optometrist will then combine those results to provide you with a prescription for the clearest vision possible. Your doctor will also perform a slit lamp exam which utilizes a special microscope with a bright light that will help them confirm the eyes are healthy and the blur is not being caused by another disease.
What are the treatments for astigmatism
Eye glasses or contact lenses are commonly used to correct astigmatism. They refocus light on the retina that is in the back of your eye for clearer vision. There are two main types of contact lenses. The most common are soft lenses and the other being hard lenses, or rigid gas permeable lenses referred to
as RPGs. Someone with irregular or more severe astigmatism may benefit from RPG lenses. Refractive surgery is another way to correct astigmatism. It uses an excimer laser to reshape the cornea and adjust how light travels through to the retina.
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