Purpose: To test the hypothesis that daily use of zinc-monocysteine (ZMC) supplement will be well tolerated and result in improved macular function in persons with dry age-related macular degeneration (AMD).
Methods: Eligible, consenting subjects were randomized to either ZMC 25 mg or placebo twice daily for 6 months. Both ZMC and placebo groups enrolled 40 participants, with best corrected visual acuity 20/25 to 20/70, macular drusen, and pigment changes. Masked personnel determined baseline, 3- and 6-month best-corrected visual acuity, contrast sensitivity, and light flash recovery time. Differences between ZMC and placebo were analyzed by a one-sided unpaired t-test of the paired differences between baseline and 3- and 6-month timepoints for right and left eyes separately.
Results: By 6 months the ZMC group showed improved visual acuity (p < 0.0001) and contrast sensitivity (p < 0.0001). Macular light flash recovery time shortened in the ZMC group at 3 months by 2.1 sec (left eye, p = 0.0001) to 3.6 sec (right eye, p < 0.0001), and at 6 months by 7.2 sec (left eye, p < 0.0001) to 7.4 sec (right eye, p < 0.0001). This variable had no improvement in the placebo group. ZMC had a gastrointestinal irritation rate of under 2%.
Conclusion: ZMC 25 mg twice daily was well tolerated and was associated with improved macular function in comparison to a placebo in persons with dry AMD.