Conclusions: While myopia has been recognized as a positive prognostic factor for normal tension glaucoma (NTG) progression in the adult population, some myopic NTG eyes exhibited significant progression within 2 years when left untreated, even under low intraocular pressure (IOP).

Objective: To determine the natural history and risk factors associated with progressive retinal nerve fiber layer (RNFL) thinning in previously stable, treatment-naïve, patients with NTG with myopia.

Methods: This study included 111 myopic NTG eyes without IOP-lowering treatment for at least 1 year and without disease progression during the treatment-free period. The RNFL thickness was measured, and a visual field test was performed every 6-12 months for >2 years. Patients with progressive changes were classified as the P(+) group, whereas those without progression were classified as the P(-) group. Cox proportional hazards model assessed risk factors of progression, whereas linear regression determined factors associated with the rate of RNFL thinning.

Results: Progressive change was observed in 25 of the 111 participants [P(+) group, 22.5%]. A family history of glaucoma, higher mean IOP, and maximum IOP during the follow-up were significant factors both for being in the P(+) group and for a faster RNFL thinning. None with a mean IOP <11 mm Hg were in the P(+) group. Davies test identified that 14.2 mm Hg was a significant breakpoint ( P = 0.042), above which the rate of RNFL thinning increased significantly with the mean IOP ( R2 = 0.252, P = 0.034).

Conclusions: Patients with myopic NTG untreated for IOP, especially those with a family history of glaucoma or higher IOP, are at increased risk of progression. Early treatment initiation is advised for high-risk patients with myopic NTG, even when their condition appears stable.