Over and Under Corrections
For complete information LASIK complications, visit the Consumer Guide to LASIK & Laser Eye Surgery.
The most common undesired outcomes of LASIK and other refractive surgery procedures are over-corrections or under-corrections, meaning there is residual refractive error remaining after surgery. Over-corrections and under-corrections are rarely caused by surgeon error or laser problems – they are typically due to variances in how a person's eyes heal after surgery. How your eyes respond to laser energy and how they heal after surgery play a dominant role in whether or not you achieve the visual outcome you desire after surgery.
For this reason, the terms "over-correction" and "under-correction" are somewhat misleading. More accurate terminology would be "over-response" and "under-response."
Over-correction and under-correction is more common with high prescriptions. For example, if you are highly nearsighted with a prescription of -10.00 diopters (D), a 10% under-correction would leave you with residual nearsightedness of -1.00 D. This usually causes noticeable blur, perhaps in the range of 20/40 vision. In contrast, if you are only mildly nearsighted with a prescription of -1.00 D prior to refractive surgery, a 10% under-correction results in only -0.10 D of residual nearsightedness, which would not interfere with attaining a very clear 20/20 (or even 20/15) result.
Your eye doctor or refractive surgeon can advise you of your risk of a surgical over-correction or under-correction, based on your preoperative prescription and other factors. In most cases, these undesired outcomes can be corrected with a follow-up refractive surgery (called an "enhancement"). Enhancements are usually performed approximately 6 months after the initial surgery, after your eyes have completely stabilized.
For complete information LASIK complications, visit the Consumer Guide to LASIK & Laser Eye Surgery.