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Eye and Vision Care

Cause of eyestrain headache

04/30/2009

Question:

Hi. I have a prescription for glasses of -2.75 -0.25 x 140 and -2.25. If I don`t wear the glasses I get an uncomfortable headache, or eyestrain, behind the worst eye with the astigmatism.

What is the likely cause? How much/how often should I wear glasses? Thanks

Answer:

Often nearsighted people can read comfortably without their glasses. However, sometimes eye strain or headaches can occur. Here is some information on some possible causes.

First we need to talk about how our focusing system (the accommodative system) normally works. When we look at something that is far away, we relax our focusing system. To look at an object that is close to us, our focusing system must exert energy to focus the eyes for near. When we focus our eyes for near, our eyes also converge or turn in towards the nose. This helps to keep both eyes looking at the same object.

Now let's talk about nearsightedness. When glasses are worn to correct nearsightedness, the eye's focusing system works as described above. However, when glasses are not worn, a reduced amount of focusing effort is required to look at near, and thus a smaller amount of convergence due to this focusing occurs. Sometimes this lack of focusing convergence (accommodative convergence) can cause the symptoms you describe.

Another possible cause is that you have a slight difference in the prescription between your two eyes. This means that if you read without your glasses on, both eyes can not clearly focus on the page at the same time. This situation can also cause symptoms.

How often should you wear your glasses? That is a question that is best discussed with your eye doctor. Often if glasses prevent symptoms such as yours from occurring, wearing them all the time is a good option.

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Response by:

Andrew J Toole, OD, PhD, FAAO
Clinical Assistant Professor of Optometry
College of Optometry
The Ohio State University