ARVO 2019 Part 3 – Contact Lens Updates
In this article:
- 1 - How do various soft multifocal CL (MFCL) designs influence visual quality, vergence and accommodation function in young adult myopes?
- 2 - Near-centred multifocal soft contact lenses and the impact on childhood hyperopia
- 3 - Accommodation in MFCL
- 4 - Does reducing treatment zone size in OK lead to a change in peripheral refraction
This is Part 3 of 3 on the Annual Association for Research in Vision and Ophthalmology 2019 (ARVO) conference summary, discussing the latest and greatest in contact lens research for myopia control. Click on the headings for links to abstracts, and you'll find links to Part 1 and Part 2 of the ARVO latest at the end of this blog.
1 - How do various soft multifocal CL (MFCL) designs influence visual quality, vergence and accommodation function in young adult myopes?
Katrina Schmid (in action, below) presented our research where we compared these measurements in a single Visio distance CL to the Coopervision Misight concentric add design and continuous aspheric Coopervision Biofinity centre distance +2.50 Add and Visioneering NaturalVue designs.
We found that the Misight lens didn't significantly alter vergence, accommodation or visual quality compared to single vision. Both continuous aspheric designs similarly gave an exophoric shift (around 2 prism dioptres) in near phoria and reduced accommodative response (increased accom lag) by about 0.50D at 33cm. These designs also affected distance and near acuity more than Misight or SV. The image shows a summary of the effects.
The clinical relevance? If you don't want a BV change in selecting a MFCL, the concentric Misight design appears to be your choice. But if you do want an exophoric shift for an eso myope, then the continuous aspheric designs could be better.
My poster presentation tomorrow will delve more into the accommodation effects of these lenses and adds in a centre distance +1.50 Add lens for extra comparison.
Well done again to our top shelf student group Kristina Nova, Ben Christie, Marlin Youssef, Patrick Chan, Sarah Crouther, Olivia Nahuysen and Laura Sevil at QUT who worked their tails off on this project last year!
2 - Near-centred multifocal soft contact lenses and the impact on childhood hyperopia
Could we apply what we know about myopia progression to manage childhood hyperopia?
Ian Beasley (in picture below) has been undertaking fascinating PhD research which turns myopia control on its head - using near-centred multifocal soft contact lenses (MFSCL) to alter the pattern of eye growth in young hyperopes. So far he's found that:
- The natural pattern of axial growth in hyperopia is so minimal as to be statistically insignificant after 18 months of monitoring
- This growth rate can be increased after 12 and 18 months of near-centred MFSCL wear in both eyes
- Aniso-hyperopes wearing a near-centred MFSCL only in their more hyperopic eye are less responsive.
These results indicate that imposing relative peripheral hyperopia could indeed alter the axial and refractive course of childhood hyperopia. And while the natural growth patterns in childhood myopia and hyperopia are clearly different, perhaps this is evidence against employing centre-near MFSCL for our young myopes, although an interesting optical discussion including peripheral refraction, spherical aberration and accommodation could be had on that topic. For now, I believe the clinical message is to stick to centre distance for young myopes, and to keep an eye out for further revelations from Ian's innovative work.
3 - Accommodation in MFCL
David Atchison, Katrina Schmid and I (in top image) conducted this study with a talented group of QUT students doing the heavy lifting on data collection (well done again Josh Collins, Clare Maher, Riya Makan, Bronte Rolls, Gemma Parmenter, Evonne Nguyen & Sevanna Zhang). We investigated 4 lens types which are being / have been researched for their myopia control efficacy; CooperVision's MiSight, CooperVision's Centre D +1.50 and +2.50 Adds, and Visioneering Tech's NaturalVue. We measured the accommodative response with an autorefractor at 1m, 50cm, 33cm and 25cm to get an accommodation stimulus-response function from 1-4 D of demand. We compared this to a SV SCL and measured 20 young adult myopes with minimal astigmatism and no significant BV disorders.
The continuous aspheric designs (CD +1.50, CD +2.50 and N'Vue) all reduced the accommodation response; the young eyes 'used' the add. Despite different add powers on the label, they were not significantly different from each other in this effect. By contrast, the MiSight did not alter the accommodation response, being no different to SV, the eyes accommodated normally.
What does this mean? Well this wasn't a myopia control study, it was a short term repeated measures exploration, but it agrees with other authors who have found similar results in some of these designs and agreed with modelling that indicated that young eyes might 'use the add' at near and under-accommodate at near in lenses with smaller central optic zones. (Miguel Faria Ribeiro et al 2018). Miguel's modelling also demonstrated that if the young eye does under-accommodate, then the distance portions of the lens could create hyperopic defocus centrally and peripherally, presumably a bad thing for achieving myopia control efficacy.
Two weeks after I printed this poster, a paper was published by Xu Cheng (Cathy), Jing Xu and Noel Brennan indicating just that - in J&J's experimental MFCL design (not commercially available), a reduced accommodation response was correlated with a reduced myopia control efficacy. This is a landmark paper in my opinion, opening up the accommodation and BV response in CLs for further investigation.
So back to the implications of our QUT research - if MiSight doesn't alter the accommodation response, does it have the edge over other MFCLs for efficacy? Maybe. But then maybe you want to reduce the accommodation response in some kids, if they're over-active at it. And which is the bigger signal - on- or off-axis refractive state?
I'm guessing that in future we may have a measure or a combo of measures of accommodation and BV (and maybe even peripheral refraction and aberrations too), which help to point out the right MFCL for the right patient. The take home message for now, I feel, is that we need to measure BV in these lenses from a visual comfort and acceptance perspective, and that this may have an influence on myopia control.
4 - Does reducing treatment zone size in OK lead to a change in peripheral refraction
Paul Gifford (below), Vinod Maseedupally, Pauline Kang and talented UNSW students Michael Tran and Courtney Priestley performed a study where a test lens with a 0.5mm smaller BOZD, altered BOZR asphericity and first peripheral curve, reduced the topographical treatment zone diameter (TZD) and was compared with a control lens and worn for 1 week in a repeated measures study design.
Did the test lens alter corneal topography compared to the control? Yes. It reduced TZD by about 1mm and increased corneal refractive power relative to the central apex at the 2, 2.5 and 3mm nasal locations but not temporal locations.
Did the test lens alter peripheral refraction (PR) compared to the control? The answer is no. The greater increase in mid-peripheral corneal refractive power along the horizontal nasal meridian failed to translate into a significant difference in change to PR profile between test and control designs.
The take home message? At this stage, if we presume the PR is driving myopia progression and is a mechanism of control, then altering OK lens design 'for myopia control' may not have the intended influence on PR. But maybe something else is going on given numerous anecdotal reports of better results with smaller OZD OK - Paul and team might be able to tell us more about this in the near future, as he's now doing some further optics analysis including pupil size interactions to compare between the lens designs.
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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