April 15, 2019
By Divya Jagedeesh, PhD student
Brien Holden Vision Institute
According to current estimates, there are 1950 million myopes and 277 million high myopes globally. Both genetics and environmental factors are the present-day main contributors to the sudden increase in myopia. Environmental factors responsible for the increase in myopia are rigorous schooling system involving lack of time outdoors and excessive near work.
Pathologic myopia is common in eyes with high myopia worse than -5.00 DS and an axial length greater than 26 mm. Pathologic myopia is associated with number of complications, vision impairment that is irreversible and impacts the quality of life and emotional well-being. So it is critical to determine those who are at the risk of developing pathologic myopia or myopic pathology to initiate preventive and early interventional measures.
Early Stage Interventions to prevent early-onset myopia: Increased time outdoors was found to be protective and decreased myopia onset. Several possible mechanisms were postulated for the protective mechanism and include: high illuminance level of light and pupillary miosis resulting in less image blur and peripheral hyperopic defocus. Another risk factor found important was excessive near work. Although difficult to intervene as near work and educational success are linked, less time spent on near work may prevent or delay onset of myopia.
Retard Myopia progression to reduce risk of high myopia: A range of interventions were found to slow myopia compared to single vision spectacles or placebo. High and low dose atropine (1% to 0.1%) were found effective, however high-dose atropine was associated with loss of cycloplegia and photophobia as well as rebound of myopia on discontinuation. Low-dose atropine is associated with fewer side effects and no rebound, however its efficacy remains uncertain. Contact lenses with added myopic defocus were shown to be promising in clinical trials and similarly orthokeratology also showed moderate effects on axial length compared to single vision spectacles. In contrast, the efficacy of spectacles on myopia progression has been limited to few lens types. The use of combination (one or more myopia control approaches) or sequential treatments remains to be explored.
Advanced stage interventions- current and novel treatments for pathologic myopia: Complications of pathologic myopia include posterior staphyloma, chorioretinal atrophy, retinal pigment epithelium atrophy, lacquer cracks, choroidal neovascularization, myopic foveoschisis, and macular hole; choroidal neovascularization being the most severe vision-threatening condition affecting 5% to 10% of highly myopic eyes. Anti-VEGF therapies using ranibizumab or aflibercept are used as first line therapies. Vitrectomy with internal limiting membrane peeling was used for macular hole with 87% to 100% success in macula closure for myopic traction maculopathies. Macular buckling is preferred over pars plana vitrectomy in cases of foveoschisis, retinal detachment, and macular hole.
More recent studies have directed their attention to sclera and collagen to counteract the progression of myopia to high myopia or pathological myopia. Scleral cross-linking techniques to reinforce sclera using chemicals activated by visible light or non-light activated chemicals are being experimented with a hope to increase scleral tissue stiffness.
Prevention and Management of Myopia and Myopic Pathology
Seang-Mei Saw, Saiko Matsumura, and Quan V. Hoang
Myopia is fast becoming a global public health burden with its increasing prevalence, particularly in developed countries. Globally, the prevalence of myopia and high myopia (HM) is 28.3% and 4.0%, respectively, and these numbers are estimated to increase to 49.8% for myopia and 9.8% for HM by 2050 (myopia defined as -0.50 diopter [D] or less, and HM defined as -5.00 D or less). The burden of myopia is tremendous, as adults with HM are more likely to develop pathologic myopia (PM) changes that can lead to blindness. Accordingly, preventive measures are necessary for each step of myopia progression toward vision loss.
Approaches to prevent myopia-related blindness should therefore attempt to prevent or delay the onset of myopia among children by increased outdoor time; retard progression from low/ mild myopia to HM, through optical (e.g., defocus incorporated soft contact lens, orthokeratology, and progressive-additional lenses) and pharmacological (e.g., low dose of atropine) interventions; and/or retard progression from HM to PM through medical/surgical treatments (e.g., anti-VEGF therapies, macula buckling, and scleral crosslinking). Recent clinical trials aiming for retarding myopia progression have shown encouraging results. In this article, we highlight recent findings on preventive and early interventional measures to retard myopia, and current and novel treatments for PM.
Saw, S. M., Matsumura, S., & Hoang, Q. V. (2019). Prevention and Management of Myopia and Myopic Pathology. Investigative ophthalmology & visual science, 60(2), 488-499.