Doctor's Answers (2)
Indeed, in some cases, LASIK or refractive surgeons may sometimes aim for slight over-correction. Often times, it may be done based on the surgeon’s understanding of his own surgical results. The aim is still to try to have the most accurate result possible.
Some surgeons may tend to under-correct or over-correct depending on certain levels of refractive error, patient-related factors or model of laser used.
This is one advantage of a laser platform that is used by a small group of surgeons or even a single surgeon whereby the results from past cases can help fine tune the surgical calculations according to the single surgeon and the specific laser machine.
Dr David Chan
To over or undercorrect, or to target zero power outcome depends on a few things:
1) Age of patient: tendency is for younger patients to target overcorrection. 0.25D to 0.5D overcorrection is common for those below 30 year old. One of the reasons is to "reserve" for future regression.
2) Consistency of refraction results: sometimes the power measurements do not completely agree, resulting in discrepancy between glasses or contact lenses worn and clinic refraction results. Refraction results may also differ with and without relaxing eyedrops.
In these cases, the surgeon may choose to follow the stronger prescription, to keep distance vision clear.
3) For patients close to 40 year old, tendency is to undercorrect in at least one eye to preserve near vision for a bit longer and delay onset of presbyopia symptoms.
Hope this clears your doubt. Cheerio!
Dr Daphne Han