The response of intraocular pressure (IOP) to hemodialysis was investigated in 55 patients with end-stage kidney disease enrolled in a chronic dialysis program. The mean level of IOP, measured by the Goldman applanation tonometer, before dialysis was slightly lower than that of a control group of 50 healthy subjects (14.9 +/- 2 mm Hg vs 15.6 +/- 1.9 mm Hg. p = .07). During dialysis IOP underwent an excessive rise (7.8 to 12.5 mm Hg) in 10 patients (group 1), remained unchanged (variations below 2 mm Hg) in 41 patients (group 2), and decreased (3.1 to 5.1 mm Hg) in 4 patients (group 3). In group 1 patients, gonioscopy showed a narrow angle between iris and lateral cornea. Conversely, the anterior chamber angle was normal in patients of groups 2 and 3. The effect of a 7-day course of acetazolamide therapy (500 mg per day orally) on IOP was investigated in group 1 patients. Acetazolamide was capable of preventing the excessive IOP rise during dialysis. The mean reduction of such a dialytic rise was 8.1 mm Hg. However, despite this effect, in these patients the IOP level after dialysis still remained significantly higher than that of patients of group 2 (18.1 +/- 1 mm Hg vs 14.9 +/- 0.8 mm Hg. p less than .0001). Acetazolamide therapy precipitated in all patients a severe metabolic acidosis (blood pH fell from 7.38 +/- 0.02 to 7.24 +/- 0.03, p less than .0001; and bicarbonate concentration from 21 +/- 2.5 mmol/liter to 12.3 +/- 2.4 mmol/liter, p less than .0001).(ABSTRACT TRUNCATED AT 250 WORDS)