Abstract
Myopia is already the most common ocular disorder in the world, and its prevalence continues to increase worldwide. Higher myopic refractive errors are associated with an increased risk of vision-threatening complications, which has led to many investigations into the underlying cause of myopia and the mechanisms of myopia progression in order to prevent or delay the onset of myopia and slow its progression. This chapter briefly reviews ocular development and emmetropization, summarizes the known risk factors for myopia onset and myopia progression, reviews current clinical interventions for controlling myopia, and provides practice management recommendations. Finally, instances of syndromic myopia, which have not been shown to be responsive to myopia control treatments, are reviewed.
TopIntroduction
Myopia is a visual condition in which light is focused in front of the retina, causing distant objects to appear blurred. It is already the most common ocular disorder in the world and is still increasing in prevalence worldwide (Holden et al., 2016), with the onset of myopia occurring earlier in life (Lin et al., 2004).
Myopia most commonly occurs during school-age years when the eyeball grows too long, as shown in Figure 1.
Figure 1.
Compared to the emmetropic eye shown in A, a myopic eye, shown in B, is elongated along the sagittal axis of the globe. This leads to a longer vitreous chamber depth and axial length
Historically, myopia has been seen as more of an inconvenience than a disease. However, the anatomical changes associated with myopia, which worsen with higher levels of myopia, are not eliminated with refractive error corrections, and any amount of myopia increases the risk of retinal detachment, myopic maculopathy, glaucoma, and other vision-threatening complications (Flitcroft, 2012). High myopia, defined as refraction greater than -6.00D, is now a leading cause of preventable blindness (Wu et al., 2015).
The myopia epidemic has prompted a renewed interest in efforts to prevent or reduce the progression of myopia, and methods of controlling eye growth are constantly evolving. Current information from the peer-reviewed literature about clinically applicable myopia control is reviewed here along with practical tips for treating children with current effective myopia control options.
Key Terms in this Chapter
Myopia: Also known as nearsightedness, a visual condition in which light is focused in front of the retina, causing distant objects to appear blurred.
Emmetropization: The genetic and optical eye growth regulatory process that eliminates most refractive error during early childhood.
Myopia Progression: The increasing magnitude of refractive error and axial length that is typically observed during school-age years.
Under-Correction: An intentional reduction in the magnitude of myopic correction that is prescribed.
Refractive Error: Myopia, hyperopia, or astigmatism resulting from a mismatch between the optical power of the eye and the length of the eye.
Myopia Control: The use of clinical treatments or environmental modifications to delay or slow the progression of myopia in children.
Orthokeratology: A method of myopia control using reverse-geometry rigid gas permeable contact lenses that are worn overnight and gently reshape the corneal surface and provides for clear distance vision.
Myopia Treatment: The prescription of glasses, contact lenses or atropine for the purpose of myopia control.
Myopigenic: Myopia-inducing, usually referring to a myopia-inducing stimulus.