Risk of posterior capsule rupture similar with kinetic and akinetic block

This extensive literature review found no clinically significant difference in the rate of posterior capsule rupture between akinetic and kinetic block techniques.

Proponents of akinetic blocks argue that immobilizing the eye makes surgery safer since unexpected eye movement is less likely to occur. Proponents of kinetic blocks argue that because their patients can look toward the light, the eye will always remain "on axis," while the lack of periocular anesthesia means that vitreous bulge is less likely.

The authors believe this is the first attempt at addressing this controversy through a review of prospective randomized trials. They searched the literature for prospective randomized studies comparing akinetic (sub-Tenon, peribulbar, or retrobulbar) and kinetic (topical, or topical and intracameral) local anesthesia for phacoemulsification surgery. Only studies that stated the rate of posterior capsule rupture or that stated without qualification that there were no intraoperative complications were included.

Fifteen papers met the inclusion criteria. The number of eyes ranged between 26 and 282 per akinetic or kinetic group.

Eleven (0.74 percent) of 1,494 eyes in the akinetic group and 11 (0.80 percent) of 1,368 eyes in the kinetic group experienced posterior capsule rupture. This difference was not statistically significant.

The authors note that this conclusion applies only to patients who would be suitable for a kinetic or akinetic block. Also the trials analyzed used only experienced phacoemulsification cataract surgeons. Therefore, they cannot be sure whether the conclusion will be valid for complex cases or trainee surgeons.

They conclude that clinicians should continue to rely on clinical judgment when deciding whether kinetic or akinetic local anesthesia or general anesthesia is the most appropriate for each case. However, these results may instill confidence in those still uncomfortable with topical anesthesia.