Axis shift was minimal after surgery through either the 2.2-mm (13.1°) or 3-mm (19.4°) incisions, and there was no significant difference in the magnitude of axis shift between groups.
In the study, all surgeries were performed through a temporally oriented, grooved clear corneal tunnel incision using a phaco chop technique, and the Infiniti system with a 1.1-mm flared tip (Alcon Laboratories).
The coaxial microphaco technique used the new ultra-infusion sleeve (UltraSleeve) while the standard coaxial phacoemulsification was performed with a 3-mm silicone sleeve. IOL implantation was performed using the SN60C cartridge (Alcon) and Royale injector (ASICO).
No eyes had limbal relaxing incisions, surgical complications, or corneal pathology that might affect keratometry readings. Use of a Steinert gauge confirmed the 2.2-mm incisions were not enlarged after IOL implantation. At the end of the procedure, IOP was set at physiologic level and competence of incision closure was tested with fluorescein. There were no cases of wound leak or hypotony on postoperative day 1 in the series.
The keratometric data were analyzed arithmetically rather than with vector analysis to reflect changes in corneal curvature with respect to with or against the wound astigmatism and shift in axis of astigmatism.
"With the very small induced changes, results from an arithmetic analysis are more meaningful from a clinical perspective," Dr. Masket said.
Easy to perform
Dr. Masket observed that he has been very pleased with the ease and outcomes of coaxial microincision phacoemulsification because it involved essentially no learning curve, and it affords stable chambers intraoperatively and excellent postoperative results.
"Any phacoemulsification surgeon can easily transition to this new technique because it is performed with almost identical surgical parameters as standard coaxial surgery and is amenable to any approach to lens removal," he said.
There are a few minor differences to consider. For incision creation, Dr. Masket indicated he favors using a dull-sided diamond blade that consistently creates a 2.2-mm incision.
"Initially, I was using a steel blade, but my measurements showed it did not create a full 2.2-mm incision, and at some point during the procedure, the incision would be inadvertently stretched and even enlarged to greater than 2.2 mm," he explained.