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The basic difference has to do with the method of epithelial removal. In order of less cellular trauma, less inflammation, less pain and risk of scarring, and a cleaner bed, these are the generally recognized categories:
“Old-fashioned PRK” – mechanically removing the epithelium with a spatula or Amoilis brush etc. No attempt made to delaminate the epi. Basically you’re sandpapering or scraping off the epithelium, which kills millions of cells in situ, causing release of cytokines and other inflammatory mediators. It might look like you have “clean edges” at the scope afterwards, but that’s a misleading view that ignores how traumatic this is to the eye. Few high-volume surface ablation surgeons are doing this anymore, because there are better modalities. Most PRK surgeons limit their ablations to no more than -6 or -7 because they recognize the pain and scarring risk
LASEK – this is what was known as “alcohol-assisted PRK” a decade ago before it became clear it’s substantively different in terms of atraumatic and vastly less Postop pain and scarring. This was invented at MEEI in 2005 by 2 of my collaborators, Juan Carlos Abbad and Jon Talamo, and popularized and published by Dimitri Azar shortly thereafter. (The Wikipedia entry on this is wrong, but every time I correct the historical record the lay editor for refractive surgery changes it back so it’s wrong, so I gave up, which is one of the problems w wiki as they use lay editors not true experts in the field). Delamination of the epi allows for a very clean and atraumatic removal, hence less inflammation -> pain -> scarring. Most high-volume surface ablation surgeons are using this method, and many upwards revised their limits to -8 or -9 (if there’s sufficient residual corneal stroma)
Epi-LASIK or epi-LASEK are the same. I’ve tried to popularize the latter term with some success, since it’s obviously more similar to LASEK rather than LASIK. An EpiKeratome is used for the delamination. Avoiding alcohol avoids alcohol toxicity to the surrounding tissues, some of which is inevitable in LASEK even if you use a well. Years ago most practitioners (myself included) stopped replacing the epithelium as they found recovery to be faster this way. Yet it’s still less traumatic and inflammatory and has a faster recovery than even LASEK. With epi some surgeons are comfortable going up to -10.
I’ve done over 15,000 surface ablations at this point and always try with my fellows to improve our techniques and outcomes. We had a fellow from Venezuela come who had a PRK two years prior. He got to 20/20 but was in agony for 10 days. His dad is a MD and owns the largest private hospital in Venezuela so he got the procedure for free. After 1 year with me he flew up his entire family, parents, brothers, sisters to NYC to get LASEK or epiLASEK with me. They must have spent $20,000 on that in just airfare and hotels and laser fees (even though we did them close to cost). That should tell you that he really came to believe that LASEK is dramatically different and better than PRK, when they could have got that for free back home. None of them had any pain, and we got them all to 20/15
ASA is Advanced Surface Ablation and refers to LASEK and epiLASEK where the epi is delaminated, to distinguish them from non-advanced PRK, where it’s simply sandpapered or scraped away
Anyway, that’s my summary of current terminology as probably the most active practitioner of surface ablation in the US, for whatever it’s worth;)

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