International Myopia Conference 2017 Part 2
In this article:
More of the latest from the sixteenth biennial International Myopia Conference (IMC) is below - read here for Part 1.
Three more fascinating areas and/or pieces of research presented at IMC, and some bonus material, are below. A more detailed write up, published in Australian industry journal Mivision, can be accessed from the link, which includes relevant references.
IMC #4 - outdoor time for myopia control (not just prevention)
In Taiwan, 20% of 7 year olds are myopic, increasing to 85% by age 18. Pei-Chang Wu presented the results of a school based intervention trialled across Taiwan called the ROC (recess outside classroom) which involved, in addition to spending breaks outside (an extra 40+ min / day), educating parents about the risks of myopia and importance of outside time, along with outdoor diaries and sticker reward systems to encourage outdoor time and breaks from near work at home. Both groups also received eye health education on myopia prevention. A total of nearly 700 Grade 1 children across 16 schools participated.
The results? Over a year, this intervention inhibited myopia progression by about 30%. This is important as previous data has indicated that outdoor time may only be beneficial to non myopic children, and not once myopia has onset - the ROC program showed a benefit for all children, both myopes and in the incidence of onset of new myopes - 8% in the ROC group compared to 18% in the control group.
The conclusion? This outdoor time stuff really works, for the at-risk pre-myope and the myope. Early interventions matter, provided they result in a change in behaviour.
IMC #5 - How do myopes use multifocal contact lenses?
This was definitely one of my favourite papers presented at IMC, and one of the most thought provoking for my questions about binocular vision and efficacy with myopia control contact lens treatments. Miguel Faria-Ribero from Portugal described his modelling of retinal image quality with dual focus contact lens (DFCL) designs for myopia control, for example the Misight (which alternates between distance and +2.00 add zones) and the DISC lens (not yet commercially available; alternates between distance and +2.50 add zones). Here's the low down:
1. If a child accommodates normally through a DFCL, then the 'treatment' add zones will be myopically defocused, which is what we want (presuming this is their mechanism for myopia control, which we don't yet understand), BUT
2. If a child uses the add and under-accommodates, then the distance portions of the lens will generate hyperopic defocus, which is probably a bad thing when judged by everything we do know about myopia progression.
So Miguel modelled whether an eye would correctly accommodate through a DFCL, based on different adds and central optical zones. He found that larger central optic zones would likely lead to more accurate accommodation, allowing the 'treatment' add zones to generate myopic defocus. By contrast, smaller central optic zones may lend themselves to using the add to accommodate, leading to hyperopic defocus from the distance zones.
Fascinating - to extrapolate, might a child accommodate more accurately through OrthoK (larger central zone) than a soft multifocal contact lens (small central zone)? Could this influence the individual response to either lens type? In future, could kids who are more likely to not properly accommodate (ie. large accommodative lag) lend themselves more to OrthoK and normal accommodators to MFCL, to maximise treatment outcomes? I think this is so fascinating that I've written even more on this for you to ponder.
It's important to note that this was monocular modelling, which was not measured on actual eyeballs. The situation would likely be very different once binocularity is taken into account - for example a child with esophoria could relax their accommodation more to avoid diplopia, regardless of any effect of central optic zone size. This research, which has since been published as a full paper, could prove the foundation of understanding how we could improve efficacy with contact lens treatments, and customise the lens to the individual patient.
IMC #6 - atropine dosage and mechanisms
Sarah Kochik from Berkeley, USA investigated dosing schedules and side effects of 0.01% atropine in young adults, finding that the biggest mydriatic effect occurred the morning after a nightly instillation, but over the course of a week there was some recovery of pupil size, even in a group on nightly dosing. The comparison group, who dosed at night twice a week, showed no significant loss in accommodation function compared to when they were untreated, while the daily dosage group did. How this would relate to myopia control is yet to be determined.
John Phillips and colleagues from the University of Auckland, New Zealand, investigated the interaction of atropine and retinal defocus on subfoveal choroidal thickness – choroidal thinning has been measured as a short term response to various myopigenic stimuli, and may be a precursor for eye growth. In Taiwanese children aged 6-14 years with low to moderate myopia, one hour of myopic defocus causes subfoveal choroidal thickening while hyperopic defocus causes thinning. After treatment with 0.3% atropine, for at least a week, hyperopic defocus no longer causes thinning, indicating that the atropine has abolished the thinning response while not interfering with the thickening response to myopic defocus. This indicates that myopia control could be enhanced by a combination of optical and pharmacological methods - exciting stuff for future clinical applications - and has since been published as a full paper.
IMC bonus bit - virtual reality!
There were further sessions on genetics, animal models, visual simulations of varying optical corrections and even the effect of virtual reality (VR) googles on binocularity by Philip Turnbull of the University of Auckland – he found minimal effect of both indoor and outdoor simulated viewing conditions in young adults with normal binocular vision, and a small measurable increase in choroidal thickness after use which could be due to heat, or a mismatch created between vergence and accommodation systems by the headsets, which could possibly indicate a therapeutic benefit. Increased uptake of VR into the future highlights another intriguing vision research opportunity. This has since been published as a full paper.
The mark of a successful scientific conference was that attendees generally left knowing less than when they arrived; with minds full of new research questions to investigate in this endlessly fascinating field.
Meet the Authors:
About Kate Gifford
Dr Kate Gifford is a clinical optometrist, researcher, peer educator and professional leader from Brisbane, Australia, and a co-founder of Myopia Profile.
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