Purpose To compare the anterior capsulotomy edge tear strength created by manual continuous curvilinear capsulorhexis (CCC), femtosecond laser-assisted capsulotomy (FLACS), and selective laser capsulotomy (SLC).
Setting Singapore National Eye Centre, Singapore and Excel-Lens, Livermore, California, USA.
Design Three armed study in paired human eyes.
Methods Capsulotomies were performed in 60 cadaver eyes of 30 donors using CCC, Victus Femtosecond Laser, (Bausch & Lomb, Rochester, New York, USA) or CAPSULaser, (Excel-Lens, Los Gatos, California, USA). Three pairwise study groups each involved 10 pairs of eyes. Study group 1: SLC eyes compared with fellow eyes with CCC. Study group 2: CCC eyes compared with fellow eyes with FLACS. Study group 3: FLACS eyes compared with fellow eyes with SLC.
A shoe-tree method was used to apply load to the capsulotomy edge, and Instron tensile stress instrument measured distension and threshold load applied to initiate capsule fracture. Relative fracture strengths and distension of CCC, FLACS and SLC were determined. Scanning electron microscopy (SEM) of capsule edges were reviewed
Results Anterior capsulotomies behave as non-linear elastic (elastomeric) systems when exposed to an external load. The pairwise study demonstrated that the SLC fracture strength was superior to that of CCC by a factor of 1.46-fold with SLC 277±38 mN versus CCC with 190±37 mN. Furthermore, CCC fracture strength was superior to that of FLACS by a factor of 1.28-fold with CCC 186 + 37 mN versus FLACS 145 ± 35 mN (p < 0.001). This was determined by statistical analysis utilising the Wilcoxon matched-pairs signed-ranks test and in accordance with the Consolidated Standards of Reporting Trials guidelines. The capsule edge of SLC on SEM demonstrated a rolled over edge anteriorly and an alteration of collagen.
Conclusions The strength of the capsulotomy edge for SLC was significantly stronger than that of CCC which and both were significantly stronger than FLACS. The relative strengths can be explained by SEM of each type of capsulotomy.
- cataract surgery
- anterior radial tears
- femtosecond laser
- capsule strength
- selective laser capsulotomy
- non-pulsatile laser
- dye laser capsulotomy
- trypan blue
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Presented at Presented in part at the European Society of Cataract and Refractive Surgeons, Vienna, September 2018.
Contributors SD wrote the manuscript. DHM was involved in study design, data and statistic analysis. S-PC and S-ET performed the experiments. RP made written contributions to portions of the manuscript.
Funding The research was partially funded by Excel-Lens and also National Medical Research Council Singapore.
Competing interests SD is a consultant and medical monitor to Bausch and Lomb manufacturer of the Victus laser used in this study. He is also an equity shareholder in Excel-Lens, manufacturer of the CAPSULaser device studied. RP and DHM are equity shareholders in Excel-Lens, manufacturer of the CAPSULaser device studied. Dr S-PC is a speaker for Bausch and Lomb.
Patient consent for publication Not required.
Provenance and peer review Not commissioned; externally peer reviewed.