Effects of Miosis on Anterior Chamber Structure in Glaucoma Implant Surgery

Abstract

We investigated changes in anterior chamber (AC) structure after miosis in phakic eyes and pseudophakic eyes with glaucoma. In this prospective study, patients scheduled for glaucoma implant surgery were examined using anterior segment optical coherence tomography before and after miosis. Four AC parameters (AC angle, peripheral anterior chamber (PAC) depth, central anterior chamber (CAC) depth, and AC area) were analyzed before and after miosis, and then compared between phakic and pseudophakic eyes. Twenty-nine phakic eyes and 36 pseudophakic eyes were enrolled. The AC angle widened after miosis in both the phakia and pseudophakia groups (p = 0.019 and p < 0.001, respectively). In the phakia group, CAC depth (p < 0.001) and AC area (p = 0.02) were significantly reduced after miosis, and the reductions in PAC depth, CAC depth, and AC area were significantly greater than in the pseudophakia group (all p < 0.05). Twenty-five patients (86.2%) in the phakia group and 17 (47.2%) in the pseudophakia group had reduced CAC depth (p = 0.004). Although miosis increased the AC angle in both groups, AC depth decreased in most phakic eyes and a substantial number of pseudophakic eyes. Preoperative miosis before glaucoma implant surgery may interfere with implant tube placement distant from the cornea during insertion into the AC.

Keywords: anterior chamber; glaucoma implant surgery; miosis; pilocarpine.

Figure 1

Anterior segment optical coherence tomography (AS-OCT) parameters. Among the four anterior chamber (AC) parameters used in this study, central anterior chamber (CAC) depth, peripheral anterior chamber (PAC) depth, and AC angle were measured using an integrated ruler and angle indicator. For the AC area, the value was measured automatically by AS-OCT.

Figure 2

Scatter plots of anterior chamber (AC) parameters in the phakia group. (A) AC angle, (B) peripheral anterior chamber (PAC) depth, (C) central anterior chamber (CAC) depth, and (D) AC area. Correlations between pre-miosis and post-miosis values in all parameters were strongly positive and statistically significant (all p < 0.001). The thin line represents Y = X.

Figure 3

Scatter plots of anterior chamber (AC) parameters in the pseudophakia group. (A) AC angle, (B) peripheral anterior chamber (PAC) depth, (C) central anterior chamber (CAC) depth, and (D) AC area. Correlations between pre-miosis and post-miosis values in all parameters were positive and statistically significant (all p < 0.001). The thin line represents Y = X.

Figure 4

Anterior segment optical coherence tomography (AS-OCT) images of representative patients in the phakia group. Top depicts pre-miotic image and bottom depicts post-miotic image. (A) Anterior chamber (AC) angle widened (27° to 32°), but central (CAC) and peripheral anterior chamber (PAC) depths became shallower after miosis (2.408 mm to 2.304 mm and 1.419 mm to 1.304 mm, respectively). (B) AC angle (43° to 36°) narrowed and CAC and PAC depths (3.448 to 3.115 mm and 2.144 to 1.839 mm, respectively) became shallower after miosis.