Smaller incision for intraocular lens implantation carries clinical benefits

June 15, 2011

Even if incision enlargement is needed for IOL implantation, 1.8-mm coaxial microincision cataract surgery offers patients measurable advantages compared with conventional 2.65-mm coaxial surgery.

The study enrolled 40 eyes of patients undergoing surgery for a nuclear cataract and <1 D of corneal astigmatism and no other ocular pathology or history of ocular surgery. They were randomly assigned to 1.8-mm C-MICS or 2.65-mm coaxial surgery performed with the same phaco system (Stellaris Vision Enhancement System, Bausch + Lomb) using the Venturi flow module and the same surgical settings.

Dr. Braga-Mele performed all of the surgeries using a quick-chop technique and implanted the same IOL (Akreos AO, Bausch + Lomb) in all eyes. However, the incision in the 1.8-mm group was enlarged to 2.65 mm for IOL delivery.

Analyses of a variety of intraoperative and postoperative parameters showed a number of statistically significant differences favoring the 1.8-mm procedure and demonstrating that it offered faster corneal and visual recovery with less surgically induced astigmatism (SIA), said Dr. Braga-Mele, associate professor of ophthalmology, University of Toronto, Ontario.

"One objection about switching to a C-MICS procedure is that implantation of many IOLs still requires enlargement of the phaco incision," said Dr. Braga-Mele, who also is director of the cataract unit, Mt. Sinai Hospital, Toronto. "The results of this study, which are probably translatable to other phaco platforms [that] allow sub-2-mm surgery, confirm there are important clinical benefits associated with the C-MICS procedure.

"These [benefits] may reflect greater anterior chamber stability using the microincisional technique that would be expected to reduce postoperative inflammation and enable more rapid visual recovery," she said. "[In addition,] perhaps more stretch and torque of the larger incision site during conventional coaxial surgery could impair wound integrity and healing and lead to increased astigmatism."

Preoperatively, the two groups were similar with respect to mean age and visual acuity, (VA) although the mean nuclear sclerotic cataract grade was significantly higher in the C-MICS eyes compared with the 2.65-mm group, 2.20 versus 1.75, respectively.

Intraoperative parameters were recorded by independent observers. Analyses of the data showed no significant differences between groups in the mean duration of the surgery, phaco time, effective phaco time, or total percent phaco. However, the volume of balanced salt solution used was significantly less in eyes operated on through the 1.8-mm incision compared with the 2.65-mm group, 36 versus 55 ml, respectively.

"It was reassuring to see there was no additional time expended or ultrasound energy used for C-MICS," Dr. Braga-Mele said.

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