Improvement of spatial contrast sensitivity threshold after surgical reduction of intraocular pressure in unilateral high-tension glaucoma.

PURPOSE: To measure the effect of a surgical reduction of IOP on the spatial contrast sensitivity threshold in eyes showing a considerably increased IOP but no glaucomatous visual field defect, on white-on-white computer-assisted static perimetry.

METHODS: Prospective clinical trial, lasting 36 months; 10 consecutive subjects with untreated IOP > or = 30 mmHg in one eye and < or =18 mmHg in the fellow eye, no evidence of field damage in both eyes, best corrected visual acuity > or =20/20 in both eyes, and scheduled for a primary trabeculectomy in the eye showing a high IOP. The spatial contrast sensitivity threshold was measured before surgery and at each follow-up visit.

RESULTS: Preoperative spatial contrast sensitivity was worse in those eyes bearing a high IOP relative to the normal fellow eyes (paired samples t-test, P <0.0005). An improvement of contrast sensitivity threshold, exceeding the 95% confidence limits of the preoperative test-retest variability, was observed at 3, 6, and 12 cyc/deg in each surgical eye at the end of follow-up. No change was observed in the fellow untreated normal eyes. The improvement correlated directly with the amount of decrease in pressure obtained by surgery.

CONCLUSIONS: Eyes with no field defects on white-on-white computer-assisted static perimetry, but bearing a IOP > or = 30 mmHg, show a decreased spatial contrast sensitivity. A surgically obtained reduction of IOP is paralleled by an improvement of spatial contrast sensitivity.