Preoperative iris configuration and intraocular pressure after cataract surgery

To determine predictors of long-term intraocular pressure (IOP) after cataract surgery.

Hunter Holmes McGuire Veterans Administration Hospital, Richmond, Virginia, USA.

Case series.

Clinical variables, IOP by applanation tonometry, anatomic features on anterior segment optical coherence tomography (AS-OCT), and gonioscopy were assessed before and after uneventful cataract surgery in eyes with open filtration angles. Multivariate linear regression of preoperative measurements was used to predict the mean IOP from 2 to 18 months postoperatively.

The study enrolled 77 eyes (77 patients). Prediction of the mean postoperative IOP improved when up to 4 preoperative IOP values were averaged (r(2) = 0.20) compared with using the final preoperative IOP value only (r(2) = 0.13). The mean iris cross-sectional area decreased after surgery, from 3.84 mm(2) to 3.70 mm(2) (P=.01). The mean convex hull of the iris segments also decreased, from 5.05 mm(2) to 4.19 mm(2) (P<.001). The mean postoperative IOP was independently predicted by the preoperative average IOP, primary open-angle glaucoma, and the convex hull of cross-sectional iris segments (P=.001, model r(2) = 0.38) or iris cross-sectional area (P=.003, model r(2) = 0.36). Phacoemulsification parameters, incision type, and anterior chamber angle and depth did not predict postoperative IOP.

Averaging up to 4 preoperative IOP values improved postoperative IOP predictions. A high iris cross-sectional area or convex hull of the iris segments on AS-OCT was associated with lower postoperative IOP. These findings might help identify patients who are likely to have the largest IOP drop after cataract surgery.