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Residual refractive errors
Residual refractive errors are the differences between the intended refractive correction and the actual refractive correction. Refractive surgeons generally aim for 20/20 vision (good vision without glasses or contacts). But since sculpting human eye tissue is a bit like sculpting Jell-O, many people don't wind up with perfect 20/20 vision.
There are numerous types of residual refractive errors.
Most people who do not achieve 20/20 vision after the first surgery have several options. They can wear glasses or contact lenses to correct the remaining refractive error, or they can choose to undergo additional surgery to correct the residual refractive error (provided their corneas have enough thickness to allow the removal of more tissue). Additional surgery usually comes with a risk level similar to the original surgery.
Some people can achieve 20/20 vision on a high contrast eye chart but still have horrible vision. If the area of correction placed on the eye is smaller than the pupil, one may experience glare, arcing, starbursts and/or halos (commonly called “GASH”). Others are left with a “bumpy cornea” (called “irregular astigmatism” and/or “higher order aberrations” (HOAs) that cause the light to scatter as it enters the cornea. When this happens, the patient will see multiple images with each eye. There is no reliable surgical fix for these problems at this time, although technology continues to advance. Since glasses and soft contact lenses usually cannot mask these problems, gas permeable rigid contact lenses (“RGPs”, aka “hard lenses”) are the only option for this group of patients. Fitting prosthetic RGPs after refractive surgery can be challenging (due to the changed curvature of the cornea) and not everyone is able to wear these lenses successfully.
There are also other types of residual refractive errors. Please see the articles in this section for information about each type of visual/optical complications and their treatment and management.
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