This article is more than 5 years old. Information may no longer be current.
Lenticule extraction procedure leaves cornea stronger, can be used for higher level of myopic correction
Click Here to Manage Email Alerts
AMSTERDAM — The small-incision lenticule extraction technique preserves total stromal tensile strength better than other refractive procedures and can therefore be safely used for higher levels of myopia, according to a specialist.
“With SMILE the anterior part of the stroma, which is the strongest, is not being cut. You only cut the intermediate lamella,” Dan Reinstein, MD, said at the European Society of Cataract and Refractive Surgeons meeting.
Dan Reinstein
In PRK and LASIK, the anterior cut and tissue ablation subtract tensile strength from the stroma. The total remaining tensile strength is calculated on the quantity of stromal tissue that remains below the ablation.
“In SMILE, you only cut an intermediate lamella, and the tensile strength is the summation of what is above and below the lenticule,” Reinstein said.
Based on a mathematical model, the remaining total tensile strength (TTS) of a cornea following PRK, LASIK and SMILE was calculated.
“In a 550µ cornea after 100µ tissue removal, postoperative TTS was 75% for SMILE, 68% for PRK and 54% for LASIK. The postoperative TTS decreased for thinner corneal pachymetry for all treatment types,” Reinstein said.
For LASIK, the postoperative TTS decreased with increasing flap thickness by 0.22%/µ, but increased by 0.08%/µ for greater cap thickness in SMILE.
“The model predicted that SMILE lenticule thickness could be approximately 100µ greater than the LASIK ablation depth and still have equivalent corneal strength. Consequently, SMILE should be able to correct higher levels of myopia,” he concluded.
Dislclosure: Reinstein is a consultant for Carl Zeiss Meditec.