GLASSES AND REFRACTIVE ERROR
The most common reason for blurred vision in patients of all ages is a condition called refractive error. Refractive error results in blurred images, at either distance or near, because the shape of the eye, and the size of the eye are not ideal. Approximately 20-40% of the public has refractive error to some degree. Since the length of the eye cannot be altered, refractive error is corrected with glasses, contacts or refractive surgery by changing the curvature of light as it enters the eye. To find out more about refractive surgery click on the link above. Glasses and contacts allow images to become clear to the wearer by changing the curvature of light entering the eye, making it ideal for that patient’s eye size.
There are three basic types of refractive error: nearsightedness (myopia), farsightedness (hyperopia) and astigmatism. Patients who are nearsighted are able to see clearly at short distances, but cannot see objects far away. Patients who are farsighted see better at distance than nearby. The exceptions to this rule is for very young kids, who are able to see far and near without glasses even though they are farsighted, and for people who have extreme hyperopia, who cannot see either at distance or near without glasses. If a patient has astigmatism, the surface of their eye is warped and images subsequently become warped as they travel into the eye. People with even a modest amount of astigmatism do not see well either at a distance or nearby without glasses.
Another condition, called presbyopia, also requires a patient to use glasses. This condition is an age-related change that typically affects patients around the age of 45. Presbyopic patients typically require glasses to read, when they previously did not require any glasses. To find out more about presbyopia click the link above.
When a patient comes in for an eye exam, an important part of the exam is the evaluation of the patient’s vision. If patients don’t see at least 20/30 or better, a refraction will be performed. A refraction is a non-invasive process to determine if a patient has any refractive error. Lots of conditions can cause blurred vision, such as a cataract, dry eye or glaucoma. However, since refractive error is by far the most common cause, it will be measured first. If a patient has a significant amount of refractive error, as in myopia, hyperopia or astigmatism, an eyeglass prescription will be given to correct the error.