Understanding the Link between Myopia and Glaucoma- Clues from Intraocular Pressure and Optic Discs

Myopia (near-sightedness) has become a significant public health concern, as its prevalence continues to increase in the United States and around the world. Further, myopia is also linked to potentially blinding ocular disease. Growing evidence from a number of studies links myopia with an increased risk of glaucoma, a leading cause of irreversible blindness. Eyes with primary open angle glaucoma typically exhibit high intraocular pressure (IOP) and altered diurnal IOP rhythms. The structural organization of the lamina cribrosa (LC) of the optic nerve head may also render eyes more vulnerable to nerve fiber damage, the origin of vision loss in glaucoma. One or more of these factors may also contribute to the increased risk of glaucoma in myopic eyes. IOP could play a role in normal ocular “growth” (enlargement), by exerting a stretching influence on the scleral wall of the eye. During myopia development and progression, scleral remodelling is upregulated, rendering it more susceptible to the stretching influences of IOP, with eye enlargement accelerating as a consequence. The converse that ocular elongation can be slowed by decreasing IOP and so the tension experienced by the sclera was tested in a set of experiments using a topical ocular hypotensive drug, specifically latanoprost. Its effects on both normal and “myopic” ocular growth in guinea pigs undergoing monocular form deprivation were examined, and treatment-induced ultrastructural changes in the sclera were quantified. With advances in high-resolution imaging and electron microscopy, we were able to characterize the effects of the above ocular hypotensive drug on the microarchitectural changes in the sclera and optic nerve head, including the LC. Our results demonstrate that daily topical latanoprost is effective in both lowering IOP and slowing myopia progression in myopic guinea pig eyes. It also seems to protect the myopic scleral remodelling. These findings will open the opportunities to explore lowering IOP as a myopia control treatment option that may also reduce any future risk of glaucoma in myopic children