Bevel-down phaco tip position associated with increased endothelial cell loss

J Cataract Refract Surg. 2011;37(11):1971-1976

Placing the phacoemulsification tip in the bevel-down position during cataract surgery may result in increased endothelial cell loss, a study found.

In a prospective, randomized trial based out of Tehran, Iran, 30 eyes underwent stop-and-chop phaco using the conventional bevel-up position and another 30 underwent the procedure with the phaco tip in the bevel-down position.

All known risk factors for endothelial cell damage were the same between groups. There were no significant differences in age, sex, anterior chamber depth, axial length or effective phaco time.

At 3 months postop, both groups exhibited a significant decrease in endothelial cell density; however, mean loss was 5.9% in the bevel-up group and 13.6% in the bevel-down group (P = .012). While a significant decrease in the percentage of hexagonal cells occurred, this percentage and the coefficient of variation in cell size did not differ between groups.

The study authors postulated that endothelial cells may be more vulnerable to released energy in the bevel-down position because with this positioning, phaco occurs more closely to the endothelial cells.

"This result is probably due to the emulsification of the nucleus that takes place in the vicinity of the endothelial cells when the phaco tip is in the bevel-down position. Better occlusion of the phaco tip with superficial parts of the nucleus in the bevel-down position and fear of posterior capsule damage may force placement of the phaco tip nearer to the posterior surface of the cornea, leading to endothelial cell damage," they said.