Purpose <p>This study evaluated the efficacy, safety, and tolerability of a single-dose, preservative-free (PF) Dorzolamide/Timolol combination (Twinzol-SDU).</p> Methods <p>A 3-month single-arm, multicenter, prospective cohort study was conducted in Egypt between January 2021 and October 2022 on previously diagnosed and controlled patients with ocular hypertension and/or glaucoma. Efficacy was assessed using the change in intraocular pressure (IOP) after 6 and 12&#xa0;weeks. Safety was identified through the change in the incidence of ocular side effects, ocular surface disease index (OSDI) scores and grades, and Time Break-Up time (TBUT).</p> Results <p>A total of 382 patients were enrolled in the analysis. After the three-month period of therapy, a significant reduction in IOP was seen (mean change: -1.9, <i>P &lt; </i>0.001) after switching to PF Dorzolamide/Timolol combination. The rate of ocular abrasion decreased significantly from 30.6% to 1.3% (<i>P &lt; </i>0.001). The rate of normal aqueous tear production increased from 24.1% to reach 79.4% (<i>P &lt; </i>0.001). The OSDI scores decreased significantly throughout the study period, with a median score decreased from 41.7 (21.7) to 12.5 (12.5) (<i>P &lt; </i>0.001). Mild OSDI grades significantly increased from the baseline of 12.6% to reach 24.7%. Moderate OSDI grade decreased at the same rate, from 12.8% to 11.1%. The number of patients with severe OSDI grade substantially decreased from 64.4% to 4.5%, with a <i>P &lt; </i>0.001. TBUT increased from 9 (3.7) seconds to reach and 12.3 (4) seconds after 12&#xa0;weeks of treatment (<i>P &lt; </i>0.001).</p> Conclusion <p>Generally, the PF dorzolamide/timolol combination was associated with a significant reduction in IOP and tolerability among glaucoma patients.</p>