Intraocular lens power changes after mitomycin trabeculectomy

Purpose: To evaluate biometric changes after mitomycin C augmented trabeculectomy and their effect on intraocular lens (IOL) power calculation using different formulas. Methods: In this prospective, interventional case series study, 34 eyes of 31 phakic glaucoma patients who were scheduled for primary trabeculectomy were enrolled. Using a noncontact biometry device (Lenstar, Haag-Streit AG, Koeniz, Switzerland), axial length (AL), mean corneal power, and IOL power were calculated with the Hoffer Q, Holladay, and SRK/T formulas 1 day before surgery and compared to those obtained 3 and 6 months after the operation. Bland-Altman plot was used to determine agreement between preoperative and postoperative IOL power values. Results: The AL was significantly decreased at month 3 (-0.14 ± 0.13 mm) and month 6 (-0.14 ± 0.15 mm) as compared to baseline values (both p values <0.001). Mean corneal power increased significantly at month 3 (0.41 ± 0.46 D; p<0.001) and month 6 (0.27 ± 0.47 D; p = 0.008). Using different formulas, IOL power did not change significantly after the operation (all ps≥0.17). The IOL power changes using the Hoffer Q formula were -0.09 ± 0.76 (p = 0.505) and 0.14 ± 0.9 D (p = 0.442) at 3 and 6 months, respectively; corresponding values were -0.1 ± 0.75 (p = 0.427) and 0.16 ± 0.79 D (p = 0.319) for Holladay and 0.01 ± 0.64 (p = 0.895) and 0.2 ± 0.71 D (p = 0.17) employing the SRK/T formula. Conclusions: Despite significant changes in AL and corneal power after trabeculectomy, IOL power calculation remains unchanged; therefore adjustment of IOL power calculation after trabeculectomy seems unnecessary.