Evaluation of the Mechanical Properties of the Anterior Lens Capsule Following Femtosecond Laser Capsulotomy at Different Pulse Energy Settings

PURPOSE: To evaluate and compare the mechanical properties of anterior capsule opening performed with femtosecond laser capsulotomy at different energy settings in ex vivo porcine anterior lens capsule specimens. METHODS: Twenty-five fresh porcine eyes per group were included in the study. Femtosecond laser capsulotomy was performed with three different pulse energy levels: 2 µ J (low energy group), 5 µ J (intermediate energy group), and 10 µ J (high energy group). The capsule openings were stretched with universal testing equipment until they ruptured. The morphologic profile of the cut capsule edges was evaluated using scanning electron microscopy. RESULTS: The high energy group had significantly lower rupture force (108 ± 14 mN) compared to the intermediate energy group (118 ± 10 mN) ( P < .05) and low energy group (119 ± 11 mN) ( P < .05), but the difference between the intermediate energy and low energy groups was not significant ( P = .9479). The high energy group had significantly lower circumference stretching ratio (144% ± 3%) compared to the intermediate energy group (148% ± 3%) ( P < .05) and low energy group (148% ± 3%) ( P < .05), but the difference between the intermediate energy group and low energy group was not significant ( P = .9985). Scanning electron microscopy images showed that the edge was only serrated with low and intermediate energy, but additional signs of collagen melting and denaturation were observed at high energy. CONCLUSIONS: Anterior capsule openings created at a high energy level were slightly weaker and less extensible than those created at low or intermediate levels, possibly due to the increased thermal effect of photo-disruption. [ J Refract Surg. 2015;31(3):153–157.]