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

PUKPOSE. 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 ≥ 30 mm Hg in one eye and <18 mm Hg in the fellow eye, no evidence of field damage in both eyes, best corrected visual acuity ≥ 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 ≥ 30 mm Hg, show a decreased spatial contrast sensitivity. A surgically obtained reduction of IOP is paralleled by an improvement of spatial contrast sensitivity.