October 2008




Divide & conquer

by Matt Young EyeWorld Contributing Editor


Divide-and-conquer vs. phaco-chop: What you should know now

• A new study found that phaco-chop delivers less energy to the anterior chamber. • However, the same study found that endothelial cell loss between the groups is statistically insignificant. • The study author suggests that divide-and-conquer, although it is an older technique than phaco-chop, is as safe.

Source: Allan Storr-Paulsen, M.D.


In his book Phaco Nightmares: Conquering Cataract Catastrophes, Amar Agarwal, F.R.C.S., joint managing director, Dr. Agarwal’s Eye Hospital, Chennai, India, suggested that chopping techniques have been replacing divide-and-conquer ones because they require “less ultrasound energy, operative time, and intraocular manipulation.” He cited other researchers that found “horizontal pure phaco-chop techniques used less ultrasound and had less loss of endothelial cells.” Dr. Agarwal concluded, “In our opinion, the phaco-chop technique will be the future of cataract surgery.”

A new study, however, suggests that phaco-chop and the earlier divide-and-conquer method largely are equivalent in terms of endothelial cell loss. “We found no difference in endothelial cell loss between the 2 surgical techniques, suggesting that phacoemulsification using the current divide-and-conquer technique is as safe as the more recently developed phaco-chop technique,” wrote lead study author Allan Storr-Paulsen, M.D., department of ophthalmology, Frederiksberg University Hospital, DK-2000 Frederiksberg, Denmark. The study was published in the June 2008 issue of the Journal of Cataract & Refractive Surgery.

Chopping vs. conquering

Sixty eyes of 60 patients underwent phacoemulsification as part of this study. Half of them underwent divide-and-conquer, and the other half was subjected to phaco-chop. Phacoemulsification energy was higher in the divide-and-conquer group. The mean total phaco energy was 3.98 +/– 2.5 (SD) in the phaco-chop group and 12.79 +/– 8.6 in the divide-and-conquer group, and the difference was very statistically significant. Pre-op cell density was similar in the two groups (2742 +/– 424 cells/mm2 in the phaco-chop group and 2747 +/– 330 cells/mm2 in the divide-and-conquer group).

Post-op, the groups had similar levels of endothelial cell loss. “The mean cell loss was 173 cells/mm2 (6.3%) and 155 cells/mm2 (5.7%) at 3 months and 12 months, respectively, in the phaco-chop group and 138 cells/mm2 (5.0%) and 94 cells/mm2 (3.5%), respectively, in the divide-and-conquer group,” Dr. Storr-Paulsen wrote. “The difference between the 2 groups was not significant at either follow-up.”

Further, there was no significant change in endothelial cell size variance, percentage of hexagonal cells, or central corneal thickness. “Univariate regression analysis of the associations between cell loss and age, ACD [anterior chamber depth], method of fracturing the nucleus, firmness of the nucleus, AL [axial length], volume of irrigation solution, and total phaco energy found that only shorter AL had a positive correlation with higher endothelial cell loss,” Dr. Storr-Paulsen wrote. Dr. Storr-Paulsen suggested that surgeons have correlated divide-and-conquer’s higher energy delivery with more endothelial cell loss unnecessarily. “Studies report that the phaco-chop technique requires less total phaco energy than the divide-and-conquer technique, although none of the studies evaluated endothelial damage,” Dr. Storr-Paulsen reported. “It has been postulated that less total energy leads to less endothelial cell damage. This positive correlation was confirmed by some, but not by others.”

Dr. Storr-Paulsen’s study results related to endothelial loss should give surgeons who are using the divide-and-conquer technique a breath of fresh air. “The current divide-and-conquer technique is as safe as the more recently developed phaco-chop technique,” he concluded. But why would endothelial cell loss be relatively equivalent between the two groups? “The divide-and-conquer technique delivers more US [ultrasound] power behind the iris than the phaco-chop technique,” Dr. Storr-Paulsen reported. “Furthermore, the phaco-chop technique requires a longer period of manipulation of fragments in the anterior chamber than divide-and-conquer surgery, in which most manipulation takes place behind the iris. This may be why we observed similar endothelial cell loss with both methods, despite significantly less total phaco energy.”

John Sheppard, M.D., professor of ophthalmology, microbiology, and immunology, Eastern Medical School, Norfolk, Va., is in agreement with the study results. “I use divide-and-conquer,” Dr. Sheppard said. “They are both excellent techniques with a low percentage of endothelial cell loss.”

Editors’ note: Dr. Agarwal did not indicate any financial interests related to his book. Drs. Storr-Paulsen and Sheppard have no financial interests related to their comments.

Contact Information

Agarwal: +91-44-2811-6233, dragarwal@vsnl.com

Sheppard: 757-622-2200, docshep@hotmail.com

Storr-Paulsen: allanstorr@dadlnet.dk

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