Relationship of immediate intraocular pressure rise to phaco-tip ergonomics and energy dissipation

To evaluate the rise in intraocular pressure (IOP) after phacoemulsification using a straight microtip or a Kelman microtip and its relationship to phaco energy delivered to the eye.Iladevi CataractIOL Research Center, Ahmedabad, India.This prospective randomized study comprised 48 consecutive age- and sex-matched patients with senile cataract. Inclusion criteria included older than 45 years and presence of any type of cataract from grade I to III. The patients were divided into 2 groups: straight microtip and Kelman microtip. Each group comprised 13 men and 11 women. The mean age was 58.29 years +/- 6.46 (SD) in the straight microtip group and 60.05 +/- 8.45 years in the Kelman microtip group. The IOP was measured preoperatively and postoperatively with a pneumotonometer and applanation tonometer. One surgeon performed all operations using a standardized surgical technique and topical anesthesia. The intraoperative mean phaco power and ultrasound (US) time were noted. The effective phaco time (EPT), percentage of IOP rise, and wound-site thermal injury (mild, moderate, or severe) were calculated. The correlation between the EPT and percentage of rise in IOP was evaluated using correlation coefficients and the paired t test.The mean preoperative IOP was 13.73 +/- 2.89 mm Hg in the straight microtip group and 15.14 +/- 2.60 mm Hg in the Kelman microtip group. The mean US time was 239.4 +/- 1.61 seconds and 238.2 +/- 1.48 seconds, respectively. The mean phaco power was 17.37% +/- 3.28% in the straight microtip group and 17.10% +/- 5.26% in the Kelman microtip group and the mean EPT, 39.06 +/- 2.28 seconds and 40.08 +/- 0.24 seconds, respectively (P =.412). The mean rise in IOP was 111.60% +/- 37.83% in the straight microtip group and 91.29% +/- 31.85% in the Kelman microtip group. The difference between groups was significant (P.05). The correlation coefficient between the EPT and percentage of IOP rise was significant in both groups: 0.3823, straight microtip group (P.05); 0.514, Kelman microtip group (P.01). Wound-site thermal injury was noted in 3 patients in the straight microtip group and 1 patient in the Kelman microtip group.Although the amount of phaco energy dissipated in the eye was the same between the 2 groups, the percentage of IOP rise was greater with the straight microtip. The rise in IOP was correlated with the dissipated phaco energy.