Glaucoma and myopia: risk factors, pathophysiology, and treatment

Myopia is one of five most important risk factors for the development of primary open angle glaucoma (POAG) along with older age, elevated intraocular pressure (IOP), sub-Saharan African ethnicity and positive family history of glaucoma. There are a few facets to consider when we discuss myopia and glaucoma. First, axial myopia (high myopia) increases the susceptibility of the optic nerve head (ONH) to IOP-related damage, therefore POAG occurs more frequently in a physiological normal IOP range in patients with high myopia. Second, there is evidence that POAG progresses faster in high myopes when IOP is elevated due to this increased susceptibility. Third, many myopes have undergone laser corrective surgery which can lead to an underestimation in the measurement of IOP and may delay the diagnosis of POAG in this group of patients. Fourth, high axial myopia is associated with atypical optic disc appearance and myopic macular degeneration. Both can cause visual impairment and make clinical assessment of glaucoma difficult. Moderate myopia is also associated with pigmentary glaucoma which is a common sub-type of open angle glaucoma. Finally, myopic patients are at risk of retinal detachment. The surgical treatment of retinal detachment can lead to a secondary form of glaucoma and worsen pre-existing POAG. Clinicians should be reminded that patients with childhood glaucoma develop secondary myopia as a result of high IOP on very elastic developing eyes, particularly if the IOP was uncontrolled at a young age. The focus of this article is on the relationship between primary myopia and glaucoma.