Visual function and perfusion of the optic nerve head after application of centrally acting calcium-channel blockers.

Abstract

In a previous study it was shown that nimodipine 30 mg twice daily leads to an improvement in the visual field in a subgroup of normal-pressure glaucoma patients. To understand the mechanism of action of nimodipine on the visual system, the aim of this study was to examine the influence of nimodipine on different hemodynamic parameters and contrast sensitivity in healthy subjects. Thirty-two healthy subjects (21-49 years old, mean age 28 years, 10 male, 22 female) received either nimodipine 30 mg twice a day or a placebo according to the same dosage regimen in a double-blind cross-over study design. The ocular blood flow was measured by means of the ocular blood flow system, the optic nerve head blood flow with the continuous laser Doppler flowmeter (Riva), and contrast sensitivity using the MCT 8000 Multivision Contrast Tester. Measurements were taken at baseline (1T0), 120 min after initial dose (1T3) and after 3 days (3T3) of therapy with 150 mg nimodipine or placebo in total. Contrast sensitivity improved significantly throughout almost all spatial frequencies in the nimodipine-treated subjects ( P=0.01), whereas there was no change in the placebo group. Ocular blood flow and optic nerve head blood flow increased slightly but not significantly in the nimodipine group (1T0: 706.6 microl/min, 9.33 AU; 3T3: 854.3 microl/min, 9.39 AU) and remained unchanged or were even lower in the placebo group ( P>0.05). The results showed a significant increase in contrast sensitivity during treatment with nimodipine in healthy subjects. This increase in visual function, however, was not correlated with an increase in ocular or optic nerve head blood flow. Therefore, another mechanism, e.g., a direct effect on the visual system, might be responsible for the improvement in visual function in healthy volunteers under nimodipine therapy.