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What are the different refractive errors?

Answers by Dr. Melanie Thares, an optometrist at Eye Associates of Central Minnesota, located in St. Cloud


What are refractive errors and how do I know which one I am?


A refractive error is the amount of power you need in glasses (or contact lenses) to be able to see clearly, and it might be different between the two eyes. Refractive errors are the most common type of vision problems. There are three different types of refractive errors: myopia, hyperopia, and astigmatism. 


Myopia is also known as nearsightedness. It is a condition in which an image in the distance appears out of focus and blurry, while objects up close are clear. This condition occurs when the eyes are longer than normal. When the eye is longer than normal, any light that enters the eye to form an image focuses in front of the retina instead of on it and this causes an image to appear blurry. Myopia is the most common refractive error seen in children. One way to tell if your child may have undetected myopia is to see where they sit compared to an object. Children with untreated myopia typically sit close to objects such as a television or the board in a classroom. You may also notice that your child squints throughout the day to see distant objects better.


Hyperopia is also known as farsightedness. It is a condition in which an image up close appears out of focus and blurry, while objects at a distance are clear. This condition occurs when the eyes are shorter than normal. When the eye is shorter than normal, any light that enters the eye to form an image focuses behind the retina instead of on it and this causes an image to appear blurry. Like myopia, many children have untreated hyperopia. Untreated hyperopia can cause headaches, eye strain, and/or eye fatigue. Some signs that your child may need to be tested for hyperopia include squinting, eye rubbing, difficulty with prolonged near work, and a lack of interest in school.


Astigmatism is when the eye is shaped like a football versus a basketball. Astigmatism can be combined with myopia or hyperopia. It is caused by an abnormal curvature of the cornea which causes two focal points to fall in two different locations on the retina. This results in objects up close and in a distance appearing blurry. Like hyperopia, it can cause headaches, eye strain, and/or eye fatigue. One common visual distortion that individuals have with untreated astigmatism is streaky / haloed lights particularly surrounding car lights while driving. Astigmatism correction is most successful with glasses compared to contact lenses.


Refractive errors can change with time, especially during the school years. As children grow, they are most likely to shift towards myopia due to their eyes getting bigger and longer. As they change year to year it is likely to see a slow progression. If there is significant change each year, there are further treatment options beyond glasses and standard contact lenses that may slow down the progression, By the age of 20, the eyes begin to be fairly stable and there should be little progression in the prescription each year.


When looking at the prescription that your eye doctor gave you, how do you know what type of refractive error you have? If there is a negative sign in front of the first number of your prescription, this means that you have myopia and are nearsighted. If there is a positive sign in front of the first number of your prescription, this means that you have hyperopia and are farsighted. If there is a second number (listed as “cyl”) next to the number identifying if you are either myopia or hyperopia, then you have astigmatism. All three of these conditions are likely to be able to be treated with either glasses or contact lenses.  Other options include surgical procedures like LASIK and PRK. The best way to confirm your prescription and see what treatment options are right for you is to see your eye doctor for your yearly eye exams.


Find out more


Dr. Mitchell Gossman is a comprehensive ophthalmologist, along with Dr. Melanie Thares, an optometrist, at Eye Associates of Central Minnesota. The office is located at 628 Roosevelt Road, Suite 101, in St. Cloud. To make an appointment or to learn more, call 320-774-3789 or email info@eaofcm.com.


“Ask the Expert” is sponsored content (paid advertising) provided by Eye Associates of Central Minnesota. To learn how your business can promote its products and services like this, contact Sr. Perspective at 320-334-3344.

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