Refractive surgery techniques are designed to change the eye's focus and reduce or eliminate the need for glasses or contact lenses. However, there are other factors in the eye, which may affect vision quality, that are unrelated to eye focus. These factors can cause the quality of vision to vary greatly, even when a patient has 20/20 or better acuity. Contrast sensitivity measurement is the best method of quantifying the actual quality of a patients vision.
Immediately after LASIK refractive surgery, contrast sensitivity may be such that the patient's quality of vision is well below the normal range. After several weeks, or in some cases several months, the quality of vision and contrast sensitivity may recover to normal levels. For PRK refractive surgery, the amount of time required to recover to normal levels may be longer, up to six months.
