Effect of Suction Duration on LASIK Flap Thickness and Hinge Length With Use of SBK Microkeratome in Flat and Steep Corneas
Purpose
To assess the effect of prolonged suction duration on LASIK flap thickness and hinge length using SBK microkeratome in flat and steep corneas.
Methods
Fifty-six eyes of 28 patients were included and divided into 2 groups; Group-A: patients with flatter corneas (36 eyes, 18 patients) with mean keratometric readings ranging from 40.13 to 43.71 D. Group-B: patients with steeper corneas (20 eyes, 10 patients) with mean keratometric readings ranging from 43.85 to 46.72 D. One-Use-Plus SBK microkeratome was used for flap creation. For right eyes; flap was created immediately once suction is built up. In left eyes, the surgeon waited for 10 seconds after suction is built up before flap creation. Flap hinge length and flap thickness were measured using surgical caliper and ultrasonic pachymetry respectively.
Results
Clinically and statistically significant differences were observed in corneal flap hinge size between average of right eyes versus left eyes, with mean of 3.78 vs. 3.98 (p < 0.001). Mean flap thickness in both eyes did not prove to be statistically different in either surgical techniques (90.2 ± 1.68 vs. 90.07 ± 1.44, p = 0.8). When patient pool was stratified into Group-A vs. Group-B, hinge sizes were significantly larger in steeper corneas (P < 0.05 and P < 0.03 respectively). However, flap thickness in both groups was consistently unaffected by surgical procedure (P = 0.5).
Conclusion
Prolonging the engagement time between the globe and SBK microkeratome increases the length of flap hinge, especially in steeper corneas. However, this is less likely to affect flap thickness. Findings were largely different from the manufacturer’s nomogram, so further assessment on higher number of cases can help setting better guidelines.