Myopia research update

Myopia currently affects an estimated 23% of the world’s population and it is increasing in prevalence. In some parts of Asia, it is so prevalent that non-myopic patients represent the minority. There is a paucity of New Zealand epidemiological data regarding myopia prevalence, but we should expect that this global epidemic is alive and well on our shores.

The following recent journal publications should be of great interest to eyecare professionals who manage patients developing myopia.

 

Low-concentration atropine for myopia progression (LAMP) study
Yam JC et al.
Ophthalmology 2019; 126(1): 113-23.

 

Review
This is a well-designed RCT of 438 four to 12-year-old children with progressive myopia who were randomised to different doses of weak atropine eye drops (0.05%, 0.025%, 0.01%, placebo) to evaluate the effect of concentration on side effects and efficacy for myopia control.

Phase 1 data after one year of treatment is presented. Phase 2 plans a crossover of placebo children to treatment for 12 months and phase 3 will allow washout of treatment for 12 months to monitor for rebound progression.

Mean spherical equivalent change at 12 months was -0.27D, -0.46D, -0.59D and -0.81D in the respective groups.  

 

Comment
Like the ATOM2 (atropine in the treatment of myopia phase 2) study, which paved the way for the increasing use of dilute atropine drops, the LAMP study found that higher concentrations of atropine are associated with a stronger effect in reducing myopia progression. The higher concentrations were also associated with better control of axial lengthening. No adverse effects on vision-related quality of life were seen in the 0.05% group, which had the strongest clinical effect.

However, washout data needs to be obtained to determine whether the higher concentrations develop rebound myopia after cessation of the drops. In the ATOM2 study, rebound was seen in 0.1% and 1% concentrations, so it remains to be seen whether the lower concentrations used in the LAMP study will display similar issues.

To date, the ideal concentration and length of treatment is still under investigation, with most practitioners using 0.01% atropine each night for an initial duration of two years as a starting point. For more on this area, see p14.



Environmental risk factors and myopia incidence in six to nine-year-olds
Tideman JWL et al.  
Ophthalmology 2019; 126(1); 127-36.

 

Review
This paper evaluated risk factors for axial length elongation and incident school myopia in a cohort of 4,734 children in the Netherlands. The study participants underwent optical biometry, cycloplegic refraction and a questionnaire evaluation of daily activities as well as baseline demographic characteristics. Linear regression models were used to create a risk score for various environmental and ocular factors.

A strong predictor of myopia development was, as one might expect, having both parents affected by myopia. However, reduced outdoor time, no sports participation, increasing number of books read per week and more than five hours of reading per day were also significantly associated with the development of myopia. A scoring system to evaluate risk was presented in this paper.

 

Comment
This adds to the increasing body of evidence implicating lifestyle and behaviour as major factors for the development of myopia. Parent and patient education regarding behavioural modification of these factors is an important part of myopia consultation and discussion.



Myopia: is the nature-nurture debate finally over?
Morgan IG, Rose KA.  
Clin Exp Optom 2019; 102(1): 3-17.

 

Review 
This is a wonderful review article and a fascinating read. It provides a synopsis of the historical understanding of myopia from Kepler’s first recognition that myopia and education were linked, 400 years ago, through to the present-day revolution in genetic and biochemical insights into the condition.

Comment 
Our understanding of myopia has now evolved to recognise that it is an aetiologically heterogenous condition. The literature now clearly supports the notion that behavioural and environmental factors play a major role in the current global epidemic of myopia, rather than genetic influences alone. The proposition that the majority of myopia is predominantly genetically determined is outdated and needs to be re-thought.A key concept is presented that school myopia may occur due to an emmetropization mechanism operating in conditions that are increasingly unnatural, due to large amounts of near work and insufficient time outdoors in bright light.

These findings may one day translate into a public health led reform of educational systems to address the rising tidal wave of pathological myopia worldwide.

 

Dr Stuart Carroll is a consultant ophthalmologist at Auckland Eye and Greenlane Clinical Centre, with specialist knowledge in cataract and refractive surgery, strabismus and paediatric ophthalmology.

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