INTRODUCTION: To compare the 24-h intraocular pressure (IOP) control and tolerability of travoprost/timolol benzalkonium chloride (BAK)-free (TTFC) vs. latanoprost/timolol fixed combination preserved with BAK (LTFC) in open-angle glaucoma patients insufficiently controlled with latanoprost 0.005% monotherapy given once in the evening.METHODS: The authors have conducted a prospective, observer-masked, active-controlled, cross-over, comparison study. Qualified open-angle glaucoma patients who demonstrated a latanoprost-treated morning IOP (10:00 ± 1 h) greater than 20 mmHg on two separate visits were randomized for 3 months to receive either TTFC or LTFC. Patients were then crossed over to the opposite treatment for another 3 months. At the end of the latanoprost run-in and after each 3-month therapy period patients underwent 24-h IOP monitoring in the habitual position using Goldmann applanation tonometry in the sitting position during the day (10:00, 14:00, 18:00 and 22:00) and Perkins tonometry in the supine position at night (02:00 and 06:00). Selected ocular surface parameters were evaluated after each therapy period.RESULTS: Forty-two open-angle glaucoma patients completed the study. The mean 24-h baseline IOP on latanoprost was 21.5 ± 1.6 mmHg. Both fixed combinations significantly reduced the IOP at each time point, for the mean, peak and fluctuation of 24-h IOP compared with latanoprost monotherapy (P < 0.01). When the two fixed combinations were compared directly, TTFC provided significantly lower mean 24-h IOP (18.9 ± 2.2 mmHg) vs. LTFC (19.3 ± 2.3 mmHg) (P = 0.004) and significantly lower IOP at 18:00 (18.6 ± 2.5 vs. 19.5 ± 2.7 mmHg for LTFC) (P < 0.001). Further, TTFC demonstrated significantly better tear film break-up time (5.15 vs. 4.65 s), corneal stain (1.5 vs. 1.8) and Schirmer I test (9.9 vs. 9.2 mm) compared with LTFC after 3 months of therapy (P < 0.01 for all comparisons).CONCLUSION: The mean 24-h IOP lowering of TTFC was statistically more significant compared to LTFC in patients insufficiently controlled with latanoprost monotherapy. Measurement of ocular surface health and tear film status favored the BAK-free TTFC compared to LTFC.