The Myopic Normal Tension Glaucoma Treatment Study (MYNT-GTS): Protocol and Baseline Characteristics of a Randomized Controlled Trial.

Background/Objectives: To describe the study protocol and baseline characteristics of participants in the Myopic Normal-Tension Glaucoma Treatment Study (MYNT-GTS), which is a randomized controlled trial evaluating the effect of intraocular pressure (IOP)-lowering treatment on glaucoma progression in eyes with myopic normal-tension glaucoma (NTG). Methods: A prospective, multicenter, randomized controlled clinical trial and baseline cross-sectional analysis. The study enrolled 473 treatment-naïve NTG eyes with myopia (spherical equivalent ≤ -1.0 diopters or axial length [AXL] > 24.0 mm) aged 20-60 years from 9 tertiary referral centers in South Korea. Participants were randomized at a 1:1 ratio into a treated group and an untreated group managed by active surveillance, and stratified by age, baseline IOP, AXL, and visual field (VF) mean deviation (MD). Treatment was initiated or intensified when predefined structural or functional progression was detected. Comprehensive examinations including quantitative assessments of the optic nerve head structure and microvasculature, medication adherence, and quality of life were performed every 4 months during the first year and every 6 months thereafter. Glaucoma progression was assessed from the rate of circumpapillary retinal nerve fiber layer (RNFL) thinning, and the rate of VF deterioration was assessed from the MD or visual field index (VFI). Results: The 473 enrolled participants comprised 239 assigned to the treated group and 234 to the untreated group. Most of the baseline variables did not differ significantly between the groups, including age (43.1 ± 9.1 vs. 43.9 ± 9.1 years [mean ± standard deviation], p = 0.33), baseline IOP (14.9 ± 2.6 vs. 14.7 ± 2.5 mmHg, p = 0.26), AXL (26.31 ± 1.37 vs. 26.32 ± 1.34 mm, p = 0.94), global RNFL thickness (79.5 ± 11.4 vs. 80.5 ± 13.2 μm, p = 0.38), and VF MD (-2.71 ± 2.58 vs. -2.32 ± 2.52 dB, p = 0.10). Conclusions: The vast majority of the analyzed variables did not differ significantly between the treated and untreated groups at baseline, supporting the validity of the subsequent comparisons. As the first prospective, multicenter randomized controlled trial dedicated to myopic NTG, the MYNT-GTS should clarify the efficacy of IOP-lowering treatment and inform the individualized management of myopic NTG. Trial Registration: Clinical Research Information Service (CRIS), Republic of Korea, KCT0005225.