The Amoils brush also allows us better control of what epithelial tissue we remove and what we leave behind. For a large astigmatic correction, the laser produces and ellipse, so it makes sense that the surface removal should occur in the same ellipse. This is not possible when using the laser to remove the surface cells nor is it possible using a circular well with alcohol . Therefore we can save a great deal of surface cells that would otherwise be removed.
In contrast of the 7–10 seconds it takes to remove the surface cells with the Amoils brush, one large cohort study of over 1200 eyes found that using alcohol-assisted surface removal took an average of 96 seconds, and such a long elapsed time can allow for the cornea to become dehydrated, which may lead to less predictable outcomes, something we are not willing to risk. It’s interesting to note that even in this study where a much less precise mechanical removal of the corneal epithelium with a blade took place, 93.3% of these 593 patients enjoyed uncorrected visual acuity of 20/20 or better compared to 90.9% in the alcohol group was shown to be In addition, in the same study the healing time for mechanical debridement (removal of surface cells directly with an instrument, just as we do with the brush) was an average of 3.8 days versus an average of 4.2 days in the alcohol-assisted group. Though the above study did not find a statistically significant difference here, we have also seen healing times generally improved by at least 1/2 a day to 1 full day with our alcohol-free Amoil brush method. It has been postulated that using the Amoils brush may allow more rapid healing because it avoids alcohol’s toxicity to neighboring epithelial cells and corneal stroma. Several studies have also shown that post operative pain and inflammation may be reduced by avoiding the use of alcohol or the additional energy of using the laser to remove the epithelium.2
In a rabbit model, it was shown move all of the epithelium by mechanical methods created the least amount of inflammation whereas the use of the laser resulted in the most (p=0.0001) Further, The greatest loss of keratocytes (corneal cells) was observed using alcohol to remove the epithelium whereas mechanical removal resulted in the least damage (P=0.009) 3
Finally, a study out of the Army in 2014 analyzed visual acuity and haze (scarring) results in moderate to high myopes following PRK, versus, PRK with MMC, versus LASIK. The results showed that less haze (in fact no significant haze) was found in the MMC group whereas the other 2 groups had a small number of patients who developed clinically significant haze. Visual acuity salts or similar across the board and no complications arose from the use of mitomycin. This study’s results reflects the majority of the literature available over the last 10 years on the subject.4
1. Ghoreishi, M. et al. j Ophthalmic Vis Res, 2010;
2.Comparison of postoperative pain in patients following PRK versus advanced surface ablation. Blake CR et al. J Cat Ref Surg 2005; 31:1314–1319;
3.Campos, M. et al. Ophthalmology, 1994;
4.The US Army Surface Ablation Study: comparison of PRK, MMC-PRK and LASIK. Sia, RK et al. J Refractive Surg, 2014.