We thank Dr. Davidorf for his interest in our paper and input regarding the conclusions drawn from the data presented.
We agree that posterior capsule tears can potentially affect refractive outcomes through effects on IOL choice and positioning. Our reference to Chan et al.1 was to support the statement that posterior capsule tears “can have a significant effect on endothelial cell loss, glaucoma, cystoid macular edema, endophthalmitis, and retinal detachment when anterior vitrectomy is required and surgical time prolonged” rather than in reference to any effect of anterior or posterior capsule tears on refractive outcomes. As stated in our paper, “[t]he rate of posterior capsule tear was not significantly different between our femtosecond laser–assisted cataract surgery and phacoemulsification cataract surgery cohorts, even though the result was numerically greater in the femtosecond laser cohort.”
Our calculated P value was 0.14 (χ2 test) and hence reported as not statistically significant. Dr. Davidorf’s calculation at P=.06 might highlight a trend toward significance. From our data, it is not possible to determine whether the numerical difference in posterior capsule tear rates (higher in laser–assisted cataract surgery) represents no difference between cohorts or that there was insufficient power to show a statistical difference. Although posterior capsule complications are typically more clinically significant than anterior capsule complications, we agree that anterior capsule tears can also potentially affect the positioning and choice of IOL and this can be clinically relevant to refractive outcomes. As highlighted in our paper, anterior capsule complications with laser–assisted cataract surgery remain a significant concern. We believe these represent a biomechanical weakness introduced by the femtosecond laser, which creates an ultrastructural can-opener capsulotomy.2
Our study of more than 4000 eyes found that the rate of intraoperative complications was significantly higher in the laser–assisted cataract surgery cohort, despite that many of the more challenging patients (eg, small pupils) were more likely to be included in the phacoemulsification cataract surgery cohort. Therefore, we agree with Dr. Davidorf’s conclusion that the rate of intraoperative complications is higher and hence the safety lower in femtosecond laser–assisted cataract surgery. In regard to our own conclusions, our initial submission put a stronger emphasis on these valid safety concerns.
1. Chan E, Mahroo OAR, Spalton DJ. Complications of cataract surgery. Clin Exp Optom. 93, 2010, p. 379-389, Available at: http://onlinelibrary.wiley.com/doi/10.1111/j.1444-0938.2010.00516.x/pdf
. Accessed March 21, 2015.
2. Abell RG, Davies PEJ, Phelan D, Goemann K, McPherson ZE, Vote BJ. Anterior capsulotomy integrity after femtosecond laser-assisted cataract surgery. Ophthalmology