A prospective study was conducted to evaluate the effects of Ca2(+)-antagonist on the visual field in low-tension glaucoma (LTG). Twenty-five consecutive patients (50 eyes) with LTG received nifedipine at 30 mg/day per os for 6 months. Visual field was tested with an Octopus 201 (program G1) prior to and each month during the period of nifedipine administration. In addition to tonometry and the measurements of systemic blood pressure and pulse rate, the reactivity of peripheral vessels was estimated by determining the response of skin temperature of a finger to cold water (4 degrees C). Twelve eyes (six patients) showed a constant improvement of visual field as expressed by an increase in mean sensitivity (MS). Canonical discriminant analysis demonstrated that the visual field is likely to improve with systemic nifedipine in patients who are young, have a higher initial MS and lower intraocular pressure, and have less decrease in diastolic blood pressure with the nifedipine administration and better cold recovery of skin temperature after their hand is soaked in cold water.