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Ibrahim Osama Sayed-Ahmed; Corneal biomechanical changes after Small Incision Lenticule Extraction (SMILE) and Femtosecond Laser Assisted In Situ Keratomileusis (Femto LASIK) using a non contact tonometer with visualization and measurement of corneal deformation.. Invest. Ophthalmol. Vis. Sci. 2016;57(12):4873.
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© ARVO (1962-2015); The Authors (2016-present)
To evaluate and compare corneal deformation amplitude in patients prior to and following small incision lenticule extraction (SMILE) and Femtosecond laser in situ keratomileusis (Femto LASIK) using a non contact tonometer with visualization and measurement of the corneal deformation response to an air pulse with an Ultra-High-Speed Scheimpflug camera (Corvis®ST)
In this comparative study, 20 patients 40 eyes divided into 2 groups, the first group being those that underwent SMILE and the second being those who had Femto-LASIK . Corneal Deformation amplitude was recorded prior to and 3 months after corneal laser refractive surgery for myopia. Preoperative corneal hysteresis was correlated with age and preoperative central corneal thickness (CCT). Postoperative corneal hysteresis was correlated with postoperative CCT in both treatment groups. The correlations between postoperative change in hysteresis and stromal ablation/removal depth, percentage of tissue ablated/removed, optical zone and patient age were also examined. The femtosecond laser platform used for SMILE and for flap creation was theVisumax 500 (Carl Zeiss meditec) and the eximer laser platform was ALLEGRETTO excimer laser (WaveLight Laser Technologie AG).
The IOP difference was significantly lower postoperatively in both groups. In both groups the Corvis showed a significant postoperative reduction in the cord length of corneal applanation (A1 and A2), A2 time (time from starting until second corneal outward applanation), HC time (time until highest corneal concavity is reached), and highest concavity (HC) radius of curvature. A1 time decreased in group II only. The deformation amplitude and HC peak distances (distance between corneal peaks at point of highest concavity) increased significantly in both groups.The mean percentage of change in HC radius of curvature was significantly higher in group I while the mean percentage of change of HC peak distance and deformation amplitude were significantly higher in group II . It was also noted that the mean percentage of change of the deformation amplitude was higher in group II than group I.
Both Femto LASIK and SMILE substantially decreased the corneal biomechanical properties with less reduction in the SMILE group.
This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.
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