Identifying the pre-myope
There are four key principles for assessing risk of myopia onset:
- Family history – one myopic parent increases risk by three-fold, while two myopic parents doubles this risk again1
- Visual environment – less than 90 minutes a day spent outdoors increases risk, especially if combined with more than 3 hours a day spent on near work activities (outside of school time)2
- Binocular vision – Children with higher accommodative convergence (AC/A) ratios, typically seen with esophoria, have an increased risk of myopia development within one year of over 20 times.3 Accommodative lag may also be a risk factor but there is conjecture.4 Intermittent exotropia has also been associated with onset of myopia.5
- Current refraction – the most significant risk factor of this lot for future myopia is if a child exhibits 0.50D or less of manifest hyperopia at age 6-7. This risk is independent of family history and visual environment.6
In addition to this, the fastest rate of refractive change in myopic children occurs in the year prior to onset,7 so the child who is less hyperopic than age normal should be closely monitored, especially if concurrent risk factors are evident.
Identifying the myopia progressor
- Age - the younger a child becomes myopic, the faster they will progress, with children 7 years of age progressing by at least 1D per year with this halving by age 11-12.8
- Family history - children with two myopic parents have been shown to be the fastest progressors in single vision spectacle and atropine corrections, and children with one myopic parent progress less than the former but more than the child without such family history.9, 10
- Visual environment – near work at less than 20cm working distance and durations of longer than 45 minutes have been linked with more myopia progression.
- Ethnicity - Asian ethnicity has been linked to faster myopia progression8, 11
- Binocular vision – watch for esophoria, accommodative lag and intermittent exotropia. In myopia control studies of progressive addition spectacle lenses (PAL), children with esophoria in single vision spectacle control groups were found to progress more quickly, 12 and children with a larger baseline accommodative lag in the PAL groups showed statistically greater treatment effect.13 Children with lower baseline accommodative amplitude have shown a greater myopia control response to orthokeratology contact lens wear compared to normal accommodators.14 Finally, while the effect of controlling IXT on controlling myopia has not yet been studied, 50% of children with intermittent exotropia (IXT) are myopic by age 10 and 90% by age 20.5
Essentially, any myopic child is a progressor until proven otherwise! The institution of a myopia control strategy as early as possible is evidence based practice, especially by age 9. The Clinical Myopia Profile,free to download, provides a simple format for explaining these risk factors for onset and progression to parents, and to decide on a management strategy.
- Jones LA, Sinnott LT, Mutti DO, Mitchell GL, Moeschberger ML, Zadnik K. Parental History of Myopia, Sports and Outdoor Activities, and Future Myopia. Invest Ophthalmol Vis Sci. 2007;48:3524-3532.
- Rose KA, Morgan IG, Ip J, Kifley A, Huynh S, Smith W, Mitchell P. Outdoor Activity Reduces the Prevalence of Myopia in Children. Ophthalmol. 2008;115:1279-1285.
- Mutti DO, Jones LA, Moeschberger ML, Zadnik K. AC/A Ratio, Age, and Refractive Error in Children. Invest Ophthalmol Vis Sci. 2000;41:2469-2478.
- Mutti DO, Mitchell GL, Hayes JR, Jones LA, Moeschberger ML, Cotter SA, Kleinstein RN, Manny RE, Twelker JD, Zadnik K, the CLEERE Study Group. Accommodative Lag before and after the Onset of Myopia. Invest Ophthalmol Vis Sci. 2006;47:837-846.
- Ekdawi NS, Nusz KJ, Diehl NN, Mohney BG. The development of myopia among children with intermittent exotropia. Am J Ophthalmol. 2010;149(3):503-507.
- Zadnik K, Sinnott LT, Cotter SA, Jones-Jordan LA, Kleinstein RN, Manny RE, Twelker JD, Mutti DO, Collaborative Longitudinal Evaluation of E, Refractive Error Study G. Prediction of Juvenile-Onset Myopia. JAMA Ophthalmol. 2015;133:683-689.
- Mutti DO, Hayes JR, Mitchell GL, Jones LA, Moeschberger ML, Cotter SA, Kleinstein RN, Manny RE, Twelker JD, Zadnik K. Refractive error, axial length, and relative peripheral refractive error before and after the onset of myopia. Invest Ophthalmol Vis Sci. 2007;48:2510-2519.
- Donovan L, Sankaridurg P, Ho A, Naduvilath T, Smith ELI, Holden BA. Myopia progression rates in urban children wearing single-vision spectacles. Optom Vis Sci. 2012;89:27-32.
- Kurtz D, Hyman L, Gwiazda JE, Manny R, Dong LM, Wang Y, Scheiman M. Role of parental myopia in the progression of myopia and its interaction with treatment in COMET children. Invest Ophthalmol Vis Sci. 2007;48(2):562-570.
- Loh KL, Lu Q, Tan D, Chia A. Risk factors for progressive myopia in the atropine therapy for myopia study. Am J Ophthalmol. 2015;159:945-949.
- Hyman L, Gwiazda J, Hussein M, Norton TT, Wang Y, Marsh-Tootle W, Everett D. Relationship of age, sex, and ethnicity with myopia progression and axial elongation in the correction of myopia evaluation trial. Arch Ophthalmol. 2005;123(7):977-987.
- Yang Z, Lan W, Ge J, Liu W, Chen X, Chen L, Yu M. The effectiveness of progressive addition lenses on the progression of myopia in Chinese children. Ophthal Physiol Opt. 2009;29:41-48.
- Gwiazda J, Hyman L, Hussein M, Everett D, Norton TT, Kurtz D, Leske MC, Manny R, Marsh-Tootle W, Scheiman M. A randomized clinical trial of progressive addition lenses versus single vision lenses on the progression of myopia in children. Invest Ophthalmol Vis Sci. 2003;44:1492-1500.
- Zhu M, Feng H, Zhu J, Qu X. The impact of amplitude of accommodation on controlling the development of myopia in orthokeratology. Chinese J Ophthalmol. 2014;50:14-19.