Faramarzi et al.1 compared endothelial cell loss during cataract surgery using a bevel-up and bevel-down phacoemulsification tip. They showed a statistically significant difference in the mean endothelial cell loss between the 2 techniques and concluded that corneal endothelial cell loss was significantly higher with the phacoemulsification tip in the bevel-down position than in the bevel-up position. The results are somewhat surprising and may be confounded by the following factors:
First, the surgical technique was performed by a single surgeon but does not appear to have been standardized with regard to the specific position of the phacoemulsification tip during the procedure. An objective measure could be achieved by intraoperative real-time optical coherence tomography.2 It is likely that the surgeon tends to be more cautious with deeper grooves during nuclear sculpting and allows the tip to ride more anteriorly in the bevel-down technique than in the bevel-up technique. This is the most plausible explanation for the apparent increased endothelial cell loss using the bevel-down technique in this study.
Second, although there was no significant difference in the effective phacoemulsification time between the bevel-up and bevel-down techniques, the total surgical time was not calculated. This is an important parameter as irrigation, turbulence, and movement of fluids and instruments also affect the endothelial cells.3
Finally, more details on the methodology of endothelial cell measurement should be considered. It is not clear whether specular microscopy was performed by the same operator; interoperator variability has been reported to be as high as 10%. Moreover, specular images of more than 60 cells were analyzed and were all taken from the center of the cornea. Studies have shown that at least 75 to 100 cells per image and 3 images should be analyzed from the central and paracentral corneal regions.4
1. Faramarzi A, Javadi MA, Karimian F, Jafarinasab MR, Baradaran-Rafii A, Jafari F, Yaseri M. Corneal endothelial cell loss during phacoemulsification: bevel-up versus bevel-down phacoemulsification tip. J Cataract Refract Surg. 2011;37:1971-1976.
2. Hüttmann G, Lankenau E, Schulz-Wackerbarth C, Müller M, Steven P, Birngruber R., 2009. Übersicht der apparativen Entwicklungen in der optischen Kohärenztomografie: von der Darstellung der Retina zur Unterstützung therapeutischer Eingriffe [Optical coherence tomography: from retina imaging to intraoperative use - a review], Klin Monatsbl Augenheilkd, 226, 958-964.
3. O'Brien PD, Fitzpatrick P, Kilmartin DJ, Beatty S. Risk factors for endothelial cell loss after phacoemulsification surgery by a junior resident. J Cataract Refractive Surg. 2004;30:839-843.
4. McCarey BE, Edelhauser HF, Lynn MJ. Review of corneal endothelial specular microscopy for FDA clinical trials of refractive procedures, surgical devices, and new intraocular drugs and solutions. Cornea. 2008;27:1-16.