Intraocular Pressure and Glaucomatous Optic Neuropathy in High Myopia.

Purpose: To examine the association between intraocular pressure (IOP) and the prevalence of glaucomatous optic neuropathy (GON) in high myopia.
Methods: The hospital-based observational study consisted of patients treated in the Tokyo High Myopia Clinics and for whom fundus photographs and IOP readings were available. The appearance of the optic nerve head on fundus photographs was the basis for the definition of GON.
Results: Among 517 eyes of 261 patients (mean age: 62.1 ± 14.2 years; range: 13-89 years; mean axial length: 29.5 ± 2.2 mm; range: 23.2-35.3 mm), GON was present in 141 eyes (27.3%; 95% confidence intervals [CIs]: 23.4, 31.0). Mean IOP did not differ significantly (P = 0.53) between the glaucoma group (14.5 ± 3.3 mm Hg; median: 14 mm Hg; range: 8-38 mm Hg) and the nonglaucomatous group (14.7 ± 2.5 mm Hg; median: 14 mm Hg; range: 6-23 mm Hg). In eyes with an axial length of ≤27.4 mm, higher presence of GON was correlated only with higher IOP (P = 0.037; odds ratio [OR]:1.35; 95% CI: 1.02, 1.80). In eyes with an axial length of ≥27.5 mm, presence of GON was correlated with older age (P < 0.001; OR: 1.05; 95% CI :1.03, 1.08), longer axial length (P < 0.001; OR: 1.60; 95% CI: 1.34, 1.91), shorter vertical diameter of the temporal arterial arcade (P = 0.009; OR: 0.82; 95% CI: 0.71, 0.95), and longer minimal optic disc diameter (P = 0.002; OR: 3.07; 95% CI: 1.52, 6.21). If IOP was added to the model, it was not significantly associated with the prevalence of GON (P = 0.97; OR: 1.00; 95% CI: 0.91, 1.10). Conclusions: GON was associated with elevated IOP in myopic eyes with an axial length of ≤27.4 mm, while in more highly myopic eyes (axial length ≥27.5 mm), larger optic disc, longer axial elongation and older age-but not IOP mostly within its normal range-were factors associated with GON. Future studies may examine an abnormally low IOP to be associated with a lower GON prevalence in highly myopic eyes.