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Symptoms, Causes, & Diagnosis of Common Refractive Errors

Do you have difficulty reading road signs? Do you get headaches from reading a book or taking notes? If yes, you may experiencing vision impairment due to a refractive error.

A refractive error occurs when the shape of the eye prevents light from focusing directly on the retina. This can be caused by a number of things, such as the length of the eyeball being too long or too short, changes in the shape of the cornea, or a result of aging.

Thankfully, refractive errors are treatable. However, in order to treat them, your optometrist must first diagnose which refractive error you have. There are four types of refractive errors:

  • Hyperopia
  • Myopia
  • Astigmatism
  • Presbyopia


Hyperopia, or more commonly known as farsightedness, is a refractive error that causes nearby objects to appear blurry while distant ones are clear.


People with farsightedness will experience headaches or eye strain when trying to focus their vision during close work. They may also squint or feel fatigued as well.


Hyperopia occurs due to the length of the eyeball being much shorter than usual. As a result, light rays entering into the eye focus behind the retina opposed to directly on it.


The opposite of hyperopia, myopia is a refractive error that causes nearby objects to appear clear whilst distant ones are blurry. Nearsightedness (myopia) is the most common refractive error of the human eye, and rates of myopia are increasing.


Did you answer yes to having difficulty in reading road signs? Someone with myopia will have difficulty seeing at a distance and experience headaches, eye strain, and/or find themselves squinting.


Since myopia is the opposite of hyperopia, we are sure that you’ve already guessed it is caused by the eyeball being too long. This causes the light rays to focus in front of the retina.


An eye with astigmatism will have light rays focusing at multiple points opposed to a single one. This causes vision to be blurred or distorted to some extent at all distances.


Uncorrected astigmatism may cause impaired vision (at various distances), headaches, and eye strain.


Unlike hyperopia and myopia, astigmatism is not caused by the length of the eyeball. In fact, it is caused by an irregularly shaped cornea. Usually shaped like a baseball, an eye with astigmatism will have a football shaped cornea.


Presbyopia is an inescapable refractive error that naturally occurs with age. Like hyperopia, presbyopia causes near vision to be blurry.


Have you ever found yourself holding the menu at a restaurant at arms distance in order to see it clearly? Are you over age 40? Those are the most common symptoms of presbyopia. In addition, close work, such as handwriting, may cause headaches or eye strain.


Presbyopia occurs naturally with age. It is caused by the gradual thickening and loss of flexibility of the lens inside your eye.


As you can see, most of the symptoms for each refractive error is somewhat similar to another. As such, it is important to schedule an appointment with your optometrist if you notice any of the symptoms mentioned above.

During a comprehensive eye examination, the optometrist will be able to determine which refractive error is the source of your symptoms. From there, proper treatment methods will be suggested to the patient.