Factors affecting corneal incision position during femtosecond laser–assisted cataract surgery

Purpose: To compare the expected versus actual position and dimension of corneal incisions during femtosecond laser–assisted cataract surgery. Setting: Private Ophthalmic Clinic, Sydney, NSW, Australia. Design: Retrospective case series. Methods: Video recordings of femtosecond laser–assisted cataract surgery with a Lensx laser were reviewed. The deviation of the main and 2 secondary incisions from the expected position were correlated with globe tilt, globe displacement, and biometric data. The globe tilt was inferred from anterior capsule tilt. Globe displacement was measured. The Softfit contact lens thickness used in the patient interface was measured separately. Results: The primary incision internal and external exits were within 142 μm ± 70 (SD) and 151 ± 75 μm of the planned position. The dimensions and position did not correlate with biometric variables. The superior secondary incision external exit was displaced centrally (321 ± 84 μm) and the internal exit was displaced peripherally (84 ± 102 μm). The inferior secondary incision external exit was displaced centrally (278 ± 142 μm) and the internal exit was displaced peripherally (190 ± 133 μm). Multivariate analysis showed that the external and internal exits of the superior (adjusted r² = 0.36, P <.001; r² = 0.15, P <.001) and inferior secondary incisions (r² = 0.67, P <.001; r² = 0.46, P <.001) correlated with globe tilt and displacement. Conclusions: The primary incisions were close to the expected dimensions. The secondary incision position was affected by eye tilt and eccentric docking. These could potentially be improved with optical coherence tomography guidance.