Nasal trabeculo-ciliary angle and relative lens vault as predictors for intraocular pressure reduction following phacoemulsification

Abstract

Purpose To evaluate quantitative relationships between biometric measurements and expected intraocular pressure reduction following phacoemulsification. Design A prospective, comparative clinical study. Methods Forty nine candidates for phacoemulsification were included. Intraocular pressure was measured preoperatively and after 7 and 30 days. Ocular biometrics were measured using optical biometry and ultrasound biomicroscopy preoperatively and 1 month postoperatively. Results Patients were sub-grouped into open-angle glaucoma (12 eyes), angle-closure glaucoma (18 eyes), and cataract-only groups (19 eyes). The mean intraocular pressure reduction was −1.67 ± 2.73, −13.11 ± 7.98, and −7.50 ± 3.58 mmHg in the cataract-only, angle-closure glaucoma, and open-angle glaucoma groups ( p = 0.001). The delta-intraocular pressure at day 7 showed positive correlations with lens vault and relative-lens vault ( p = 0.005 and 0.001). It showed negative correlations with lens position, relative-lens position, anterior chamber depth, aqueous depth, and nasal and temporal angles in addition to lens thickness, anterior vault, nasal trabeculo-ciliary angle, and temporal-trabeculo-ciliary angle at the end of the follow-up period. Regression analysis revealed significant associations between preoperative intraocular pressure and both nasal-trabeculo-ciliary angle and anterior vault ( p = 0.038 and 0.019) and delta-intraocular pressure and both nasal-trabeculo-ciliary angle and relative-lens vault ( p = 0.001 and ≤0.001) with an area under the curve of 0.71 for relative-lens vault. For every degree decrease in nasal-trabeculo-ciliary angle, there was an expected 0.33 mmHg intraocular pressure reduction with no expected change if nasal-trabeculo-ciliary angle decreased to <22°. Conclusions The relationship between anterior-segment-biometrics could determine intraocular pressure behavior after phacoemulsification. The preoperative nasal-trabeculo-ciliary angle and relative-lens vault could be significant predictors for postoperative intraocular pressure reduction.