Most people with imperfect vision are able to name their vision issue. For example, “I’m nearsighted.” However, fewer patients actually understand what causes their refractive errors. Some people may have heard of a procedure called LASIK but are unsure of whether it can treat their specific problem.
To make matters even more confusing, some of the terms seem counterintuitive. (A patient is farsighted, but she has trouble seeing objects near her.) Additionally, doctors refer to refractive errors in clinical terms the patient might not be familiar with. In this article, we clear up questions like:
- What causes refractive errors?
- What’s the difference between presbyopia and hyperopia?
- Which refractive errors can be treated by laser vision correction?
The four main types of refractive error are myopia, hyperopia, presbyopia and astigmatism. They are all caused by irregularities in the shape and angle of light as it passes through the eye.
Light enters the eye and is focused by the cornea and the lens onto the retina. The retina then sends the image to the brain via the optic nerve. If you’ve ever focused a camera lens or a projector image, you know that the tiniest change of distance makes the difference between a clear or blurry image. Refractive errors are different ways in which those distances can be imperfect.
Descriptions of Common Refractive Errors
Clinical term: myopia
Popular term: nearsighted, shortsighted
What it means: Eyes that are longer or more curved than normal cause light to focus too early, making it come to a point before it hits the retina. As a result, close-up objects are in focus, but ones further away are blurry.
Clinical term: hyperopia
Popular term: farsighted
What it means: Eyes that are shorter or flatter than normal cause light to focus too late, making it come to a point after it hits the retina. As a result, distant objects are clear, but close-up ones are blurry.
Clinical term: presbyopia
Popular term:aging eyes
What it means:Because the effects are similar, presbyopia is sometimes confused with hyperopia. However, the causes are different. Presbyopia occurs as people age, and the lenses of the eyes lose some of their flexibility. As a result, patients have difficulty focusing on close images. Presbyopia can occur in conjunction with nearsightedness, farsightedness and astigmatism.
Clinical term: astigmatism
What it means:The clinical term is often used by laymen to describe an irregularly-shaped eye. Specifically, it means that the entire surface of either the cornea or the lens is not perfectly curved. Similar to an old, warped window, an imperfect corneal or lens surface results in an unclear visual image.
LASIK Treatment Options
LASIK is capable of correcting myopia, hyperopia and astigmatism. A technique performed with LASIK, called monovision can correct presbyopia. However, not everyone is a candidate for this procedure, and an ophthalmologist must evaluate a number of factors to determine a patient’s candidacy. These factors include the patient’s refractive error, corneal thickness and overall eye health. Additionally, a patient must be at least 18 years of age and have a stable eyeglass prescription for one year.
Each patient and her circumstances are different. Consult with a qualified LASIK specialist to see if laser vision correction is right for you.