Comparison of posture-induced intraocular pressure changes in medically treated and surgically treated eyes with open-angle glaucoma.

PURPOSE: To compare the posture-induced IOP changes in medically treated eyes with those in surgically treated eyes having open-angle glaucoma (OAG) and low IOP.
METHODS: Fifty-one posttrabeculectomized OAG eyes with a cystic filtering bleb and 51 nonoperated, medically treated OAG eyes were studied. The IOP measured with a Goldmann applanation tonometer (GAT) was 12 mm Hg or less in both groups. It was measured in the sitting and lateral decubitus positions with a rebound tonometer. The IOP was measured in the upper eye 5 minutes after assuming the lateral decubitus position.
RESULTS: The mean (SD) IOP measured with the GAT was 9.7 (1.5) mm Hg in the trabeculectomized eyes and 9.7 (1.4) mm Hg in the medically treated eyes (P = 0.892, unpaired t-test). In the surgically treated group, the mean (SD) IOP measured with the rebound tonometer was 10.3 (2.3) mm Hg in the sitting position and 11.3 (2.8) mm Hg in the lateral decubitus position (P < 0.001, paired t-test). In the medically treated group, the mean (SD) IOP measured with the rebound tonometer was 10.8 (2.0) mm Hg in the sitting position and 14.1 (2.9) mm Hg in the lateral decubitus position (P < 0.001, paired t-test). The greater IOP increase of 3.3 mm Hg in the medically treated group compared with the 1.0 mm Hg in the surgically treated group was significant (P < 0.001, unpaired t-test).
CONCLUSIONS: The lower posture-induced IOP change in the successfully trabeculectomized eyes indicates that trabeculectomy will not only lead to a decrease in the IOP but also lower the posture-induced IOP change.