Effect of dorzolamide/timolol combination on the visual field in glaucoma

To evaluate the effect of treatment for 3 years with a dorzolamide/timolol (1%/0.5%) fixed combination (DTFC) on visual field progression in patients with open-angle glaucoma.

A total of 14 consecutive patients were enrolled who had been previously treated with monotherapy or any combination of a beta blocker, carbonic anhydrase inhibitor, and/or prostaglandin analog for primary open-angle glaucoma (POAG; n=4) or normal-tension glaucoma (NTG; n=10).

Patients were switched to DTFC from their prior glaucoma therapy. The IOP was measured at intervals of 4-6 weeks, and the visual fields were examined at least twice a year for 3 years. The annual change of mean deviation (MD slope) was used to quantify visual field loss.

The mean MD value was -5.9±5.0 dB at baseline; it was -5.6±4.8 dB at 12 months, -5.9±5.0 dB at 24 months, and -5.6±5.1 dB at 36 months after switching. The mean MD slope was -0.2±0.8 dB/year before switching and 0.3±1.3 dB/year from baseline to 1 year, -0.3±1.1 dB/year from 1-2 years, and 0.3±0.9 dB/year from 2-3 years after switching. The mean MD slope from baseline to 36 months was correlated with the IOP reduction rate at 36 months after switching. Visual field progression was associated with the IOP reduction rate at 12 months after switching.

Switching to DTFC from prior glaucoma therapy improved the MD slope for at least 3 years. Reduction of the IOP after switching to DTFC was effective for delaying visual field progression. Although our study was not nonrandomized and was small in scale, the findings suggest that DTFC might have a beneficial effect on the visual fields in patients with open-angle glaucoma.