Myopia Update August 2017 – by Dr. G. Vike Vicente

Dr. Vicente is a Pediatric Ophthalmologist at Eye Doctors of Washington. In addition to his work at EDOW, Dr. Vicente is an assistant clinical professor in ophthalmology and pediatrics at Georgetown University Hospital, a visiting professor at Bascom Palmer Eye Institute, and a volunteer physician at the Children’s National Medical Center.

Over the past year there has been a lot written about the increase in myopia (nearsightedness) rates in children. Childhood myopia rates in the U.S. are up 66% in the last 30 years, so it is important that parents and caregivers understand the eye health implications of higher levels of myopia as well as treatments that are now available.

Myopia is believed to have both a genetic and environmental component. Twin studies have shown how strongly genetic myopia is. Identical twins have very similar refractive errors, however fraternal twins have very different eyeglass prescriptions.1,2   Yet, even with this strong evidence of genetics playing a role, the prevalence of myopia has increased significantly in the recent past, more than can be explained by genetics alone.   This rate varies by ethnicity and location suggesting that environmental differences may have some impact.  For example, ethnic Chinese children in Australia have a lower prevalence of myopia than in East Asia.3 The amount of indoor time and near work (for example, digital device use) may be environmental factors contributing to the rise of myopia.4

Nearsightedness or myopia, prevents patients from seeing distant objects clearly.  It is due to increased corneal curvature and/or increased eye axial length.  It can begin in childhood and worsen until the early 20’s.  (That is why LASIK should not be performed until the patient’s refractive error has stabilized.  Doctors would not know what to correct for.) Most of the worsening occurs between ages 8-12 yrs.

Since most myopic children will progress to some degree, we must remember that high myopia is not a benign condition.  It is associated with increased risks for glaucoma, retinal detachment and myopic maculopathy in adults.  Since LASIK only changes the corneal curvature, and not the axial length, it does not reduce the risk of these diseases.

Glasses have been used for 700 years to help patients see clearly by focusing incoming images onto the retina but they do not correct, treat or worsen the myopia.

So what can be done to slow myopic progression in children?  Fortunately, there are three treatment modalities.  First, diluted Atropine drops have been shown to slow myopic progression in young patients in China and are now being used in the US.5   The World Society of Pediatric Ophthalmology & Strabismus Myopia Consensus Statement noted:  “Atropine 0.01% dose appears to offer an appropriate risk-benefit ratio, with no clinically significant visual side effects balanced against a reasonable and clinically significant 50% reduction in myopia progression.”

Orthokeratology contact lenses also appear to slow axial length elongation. Like any contact lens, they carry some risk of infective keratitis. Peripheral defocusing lenses in the form of contact lenses also have a role in slowing the rate of myopic progression in a subset of children and further help our understanding of the physiologic control.

Perhaps most importantly, it is important to detect refractive errors early in order to reduce the risk of amblyopia, help patients see better and hopefully start one of the above early preventative treatments, which are known to perform better when started sooner.  The current AAP guidelines (http://www.aappublications.org/news/2015/12/07/Vision120715) reinforce the importance of early screening.

Sincerely,

G. Vike Vicente, MD

 

References

1: Invest Ophthalmol Vis Sci. 2008 Aug;49(8):3324-7. Epub 2008 Apr 11.

Adult-onset myopia: the Genes in Myopia (GEM) twin study.

Dirani M, Shekar SN, Baird PN.  Australia

2: Br J Ophthalmol. 2001 Dec;85(12):1470-6. Links

The importance of genes and environment for ocular refraction and its determiners: a population based study among 20-45 year old twins.

Lyhne N, Sjølie AK, Kyvik KO, Green A., Denmark.

3: Ophthalmology. 2013 Jul;120(7):1482-91. doi: 10.1016/j.ophtha.2012.12.018. Epub 2013 Mar 22.

Prevalence and 5- to 6-year incidence and progression of myopia and hyperopia in Australian schoolchildren.

French AN1, Morgan IG, Burlutsky G, Mitchell P, Rose KA.

4: PLoS One. 2017 Apr 27;12(4):e0175921. doi: 10.1371/journal.pone.0175921. eCollection 2017.Outdoor activity and myopia progression in 4-year follow-up of Chinese primary school children: The Beijing Children Eye Study.

Guo Y1,2, Liu LJ1, Tang P2, Lv YY2, Feng Y2, Xu L1, Jonas JB1,3.

5: Chia A, Lu QS, Tan D. Five-Year Clinical Trial on Atropine for the Treatment of Myopia 2: Myopia Control with Atropine 0.01% Eyedrops . Ophthalmology. 2016 Feb;123(2):391-9