Scanning electron microscopy evaluation of capsulorhexis in femtosecond laser-assisted cataract surgery

PURPOSE: To use scanning electron microscopy (SEM) to evaluate capsulorhexis-cut quality obtained during femtosecond laser assisted cataract surgery at different energy settings and evaluate whether there are differences between this technique and a standard manual technique. SETTING: Ophthalmology Clinic, Department of Medicine and Science of Ageing, University G. D'Annunzio Chieti-Pescara, Chieti, Italy. DESIGN: Prospective nonrandomized single blinded study. METHODS: Sixty capsulorhexes obtained using the conventional manual technique and the femtosecond laser with different laser energy settings were divided into 5 groups as follows: Group 1 (12 capsulorhexes) obtained with the manual technique and Groups 2 to 5 (each with 12 capsulorhexes) obtained with the femtosecond laser at 7.0 mu J, 13.5 mu J, 14.0 mu J, and 15.0 mu J, respectively. All samples were evaluated using SEM to compare the thickness along the capsulorhexis edge and the overall irregularity of the cut surface. RESULTS: Capsulorhexes obtained with the femtosecond laser at all energy settings were perfectly circular with negligible deformation. Group 1 and Group 2 had a significantly higher thickness and lower thickness, respectively, of the capsulorhexis edge than the other 3 groups (P<.001). There was also a statistically significant correlation between the degree of irregularity and increasing energy (P<.001). CONCLUSIONS: The use of the femtosecond laser in cataract surgery resulted in better capsulorhexis geometry and circularity than the manual capsulorhexis. The cut surface was smoother in the manual group. In the femtosecond laser groups, the degree of irregularity was higher at increasing energy settings.