In recent times, the prevalence of myopia —commonly known as nearsightedness—has become increasingly widespread in the youth, globally. Patients with high myopic prescriptions are at a greater risk (9x) of developing macular choroidal neo-vascularization and other vision debilitating diseases.
The Centre of Ocular Research & Education (CORE) at the University of Waterloo studied the general Canadian population and their findings highlight that:
- 6% of Canadian children aged 6-8 were myopic and 29% of children aged 11-13 were myopic
- If at least one parent is myopic, the chance of the child developing myopia were increased by 2.5x
- For 1 additional hour of outdoor time per week, developing myopia is reduced by 14.3%
Myopia is a multifactorial condition, influenced by both genetic and environmental factors.
Two current optical theories explain myopia progression:
- The accommodative lag theory- the eye produces insufficiently strong accommodative response to near objects, placing the plane of focus behind the retina, thereby inducing myopia.
- The peripheral defocus theory- states that while the central vision is aligned with retina, the periphery is placed behind the retina, inducing myopic eye growth.
Slowing the progression of myopia will aid in preventing high prescriptions later on in life. Some effective treatments include: spectacles, contact lenses, pharmaceutical eye drops, and environmental modifications.
Providing children with add power in their spectacles can reduce the lag of accommodation when they focus on near objects, removing the stimulus of myopic charge. Standard PALs (progression addition lens) follow the above principle and are effective for children with large lag of accommodation and esophoria at near.
Rigid OrthoK lenses not only eliminate the daily wear of glasses or soft contacts when worn overnight, they also reduce myopic progression by 45%, on average. The treatment is explained by the lenses reshaping the central cornea more than the peripheral cornea and is useful for myopes between -1.25 to – 4.00 diopters.
Another option—MiSight soft lenses—can also control myopia and are able to cover a wider range of prescriptions than OrthoK.
Atropine drops, of all options, have the highest treatment effect: 77% reduction in the progression of myopia. They may affect accommodation and the activity of scleral fibroblast. Some cons to the treatment include:
- Revert to pre-treatment levels
- Rebound effect: the cessation of the treatment can make the prescription worse
The American Pediatric Society states that the onset of myopia can be lowered through taking the following actions:
- Children under 2 should have no screen time
- Limit screen time to one hour/day for children aged 2-5
- Children over 5 should rotate between near and far activities