Association Between Corneal Deformation and Ease of Lenticule Separation From Residual Stroma in Small Incision Lenticule Extraction. Issue 9 (September 2015) - Shetty, Rohit
Abstract : Purpose: To study the association between corneal deformation (CD) and ease of lenticule separation from the stroma in small incision lenticule extraction. Methods: Thirty-six myopic eyes of 36 patients underwent small incision lenticule extraction. Preoperative refraction, intraocular pressure, central corneal thickness, and CD were evaluated with Scheimpflug imaging and air-puff applanation. Fourier transform of CD waveform was also performed. The surgeon also graded the ease of separation of lenticule surfaces from the residual stroma intraoperatively as grades 1 (low effort), 2 (moderate effort), and 3 (high effort). All the procedures were performed by the same surgeon. CD values were concealed from the surgeon. Differences between the grades were assessed with 1-way analysis of variance and analysis of covariance. Results: Mean preoperative refraction, intraocular pressure, central corneal thickness, lenticule thickness, and incision width were similar among the grades ( P > 0.05). A total of 5 of the 10 analyzed CD variables were significantly different among the grades. Among them, deformation amplitude (1.20 vs. 1.13 vs. 1.07 mm in the order of increasing grades, P = 0.001), velocity of the corneal apex at the second applanation point (−0.47 vs. −0.43 vs. −0.40 m/s, P = 0.02), peak distance (5.33 vs. 5.25 vs. 5.07 mm, P = 0.006), area under the deformation amplitude (13.40 vs. 12.84 vs. 12.06, P = 0.04), and root mean square of Fourier coefficients (0.12 vs. 0.12 vs. 0.11 mm, P = 0.005) decreased from grades 1 to 3. Conclusions: CD was inversely correlated with the ease of lenticule separation from the residual stroma and may assist in customization of the energy parameters of the laser.