Effect of carbachol on intraocular pressure in small-incision cataract surgery

Sixty patients, who underwent phacoemulsification and implantation of a folded polyHema intraocular lens were assigned to two groups. Following wound closure 0.5 ml of 0.01% carbachol or balanced salt solution was instilled into the anterior chamber. Healon was used in all eyes but evacuated from the capsular bag behind the intraocular lens and the anterior chamber. Intraocular pressure was measured the day before as well as 6 and 18 hours postoperatively. At 6 hours the mean change of intraocular pressure from baseline was -2.8 +/- 5.3 mmHg in the carbachol group compared with +4.7 +/- 8.0 mmHg in the BSS group (p < 0.0001). At 18 hours the mean change from baseline was -3.0 +/- 4.6 mmHg in the treatment group and +2.3 +/- 8.5 in the control group (p < 0.0001). Intraocular pressure exceeding 25 mmHg at 6 hours was observed in 8 (27%) eyes of the control group but none of the treatment group. At 18 hours 4 (13%) eyes of the control group and 1 (3%) of the carbachol group still had an increase of intraocular pressure. Summarizing our results we conclude that the effect of Healon on the postoperative intraocular pressure is successfully counteracted by its aspiration from the capsular bag and the anterior chamber, especially when carbachol is used for intraoperative miosis.