Associations between Intraocular Pressure or Glaucoma Medication with Axial Length and Pathologic Myopia Incidence and Progression

Objective To investigate the relationship between intraocular pressure (IOP) and anti-glaucoma medications on both the incidence and progression of myopic macular degeneration (MMD), posterior staphyloma and axial length (AXL) elongation in highly myopic (HM) eyes. Design Retrospective multi-ethnic cohort study with cross-sectional and longitudinal analyses. Subjects, Participants, and/or Controls 988 HM eyes from 518 multi-ethnic subjects assessed at the Singapore National Eye Centre (2017-2022). Eyes with glaucoma or on existing IOP-lowering therapy were excluded from the primary analyses. Secondary cross-sectional and longitudinal analyses included eyes with glaucoma to explore medication effects. Methods IOP was measured with non-contact tonometry. Logistic and linear regression models assessed associations between IOP and MMD/staphyloma presence and progression, and AXL elongation. Multivariate analysis was performed to identify independent predictors of progression, including effects of anti-glaucoma medication use. Main Outcome Measures Presence and progression of MMD and staphyloma, current AXL and AXL elongation as determined by imaging and clinical examination. Progression was defined by changes in MMD grade, atrophic lesions or structural staphyloma features over time. Results In non-glaucomatous eyes, IOP was not significantly associated with the presence or progression of MMD, staphyloma or AXL (all p>0.05). Across all eyes, longer AXL was correlated with earlier spectacle onset, worse visual acuity, longer anterior chamber depth, presence of tilted disc, superior PPA, vitreomacular traction, staphyloma, epiretinal membrane, dome-or-saddle-shaped macula and lacquer crack (p<0.05). In longitudinal analyses, baseline glaucoma medication use was significantly associated with reduced AXL elongation over time (β=–0.077, p=0.036), independent of IOP, whereas tilted disc and staphyloma presence predicted greater elongation (p<0.05). MMD and staphyloma progression were primarily associated with structural factors, including presence of sloped fovea, macular retinoschisis, epiretinal membrane, and dome-or-saddle-shaped macula at baseline (p<0.05). Conclusions IOP was not associated with PM-related structural changes or AXL in HM eyes. In contrast, use of anti-glaucoma medications was associated with reduced AXL elongation. These findings suggest the potential for IOP-independent pharmacologic modulation of AXL in HM eyes.