The Myopia Exchange
Dr Kate Gifford, a global authority on managing childhood myopia (short-sightedness) in clinical practice, discusses the latest myopia research and clinical techniques with experts from around the world.
The Myopia Exchange
Progressive vs bifocal spectacles - which is best
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Are progressive addition lenses and bifocals created equal for myopia control? How should we pick which lens type to prescribe, and what's on the horizon for our non-contact lens wearing young myopes?
Hi there and welcome to this my peer profile podcast on progressive versus bifocal spectacles. You'll listening to Kate Gifford Co founder of my Ip profile. An international might be a note of mystery, actually not really about any mystery all I'm actually all about making it easy and simple, which is what you'll find here on the website and in the Facebook discussion group, but International Myopia, nerd of simplicity didn't have the same ring to it. Anyway, let's get started on the fascinating question of progressive versus bifocal spectacles, and this is a fascinating question which takes into account the results of individual studies, differential optics and practical aspects of kids wearing glasses. Here's my take on it.
Speaker 2Okay.
Speaker 1I overall progressive addition Lens Studies for my Ip control have shown quite an impressive results when single ads are applied to all children. These results have been in the order of less than 20% efficacy. However, when these results have been examined in children with ace of fora and accommodative lag, the results become more impressive at around 40% efficacy. Studying to approach that of the contact Lens Studies. One extremely well designed study of eight Seg bifocal lenses with a plus to add and to basing prism Nhi showed an even more impressive results over two years of around 40% efficacy for the bifocal wearers and over 50% for the bifocal with prison where it's does this mean that base in prism is some sort of magic sauce maybe or maybe it was more than it helped to maintain normal binocularity when using a high add on children with Exa Foria. So I think about these kids with the plus to add a sub floors 11 ad or the floors could probably take it or leave it, but the exit polls with a plus to add and the base in prison shed better maintenance of normal binocular vision than with the ad alone.
Speaker 2Okay.
Speaker 1Now this bifocals study was also well constructed in that all of the children entering the study what confirmed progressors demonstrating at least one doctor of progression in the past year. This is good study design. If you make sure that you control group is actually progressing, you intervention is likely to be more powerful, but even so this was an impressive result and shows it. There is some role for spectacle lenses in MIP management toolkit.
Speaker 2Okay.
Speaker 1Neither is conjecture about progressive and bifocal spectacles having any useful effects from Ip control, just the same as theirs. Excellent studies debunking peripheral refraction as a factor in my IP development and progression. This is much conjecture for both of these theories and for the individual patient. That could be one primary driver to my of development and progression. It could be genetics, environment, peripheral refraction, accommodation or it could be a combination. This is what makes my IP is such a fascinating area of research and clinical practice. Individual Studies of progressive and bifocal spectacle lenses for my AP control have only played one single ad and one single lens type tool. Children, no. In practice we take a much more specific approach to the individual and perhaps this is where the variability lies between what we've seen in research and what we see in practice. There are also notice of notable study showing that Managing Isa Foria and underactive accommodation appears to sort of power up the my AP control effects of bifocal soft contact lenses and Ortho k. So it's an oversimplification to say that accommodation and hence spectacles have nothing to do with the Myopia picture. We shouldn't throw spectacle lens options out of the toolkit and for children with Isa for an accommodative lag, we can rightly presume that a significant myopathy control effect can be achieved with progressives are bifocals and these are the conditions that tend to be ones for which we would prescribe an AED anyway. Now if you want a bit more specific advice and prescribing ads for accommodative lag or Isa Foria checkout my relevant how to guides on the website with links in the summary below sound clinical practice, we've decided on our ad and we're now deciding between progressive and bifocals, which should we choose. While the bifocal study I described earlier has shown the most impressive my Ip control affects, I don't believe it's actually quite as simple as the bifocal being the hero. It was a very well designed study and binocular vision was considered through inclusion of the base in prison. So there's some belief with bifocals that the large field of inferior myopic defocus created by the ad, which is cost onto the superior retina, is the magic sauce of bifocals. However, the superior and inferior retina, I don't follow the same pattern of relative peripheral refraction. Is that measured along the horizontal retina? In fact, the vertical Meridian tends to show relative peripheral myopia, whereas the horizontal Meridian is the one that shows relative peripheral hyperopia. You're getting confused. Don't be, don't worry about getting confused because as you know about me, I like to make things simple for you. The simple message is that this stage, I don't think we know enough to say the bifocals are superior to progress is, so let's focus back on the patient in your chair and the practical considerations of how they'll use their glasses.
Speaker 2Yeah.
Speaker 1The great thing about bifocals is that the child gets straight into their full ad as soon as they look down through that near Seg. The bad thing is that the ad is all or nothing. So if the frame starts to slip down, well they look above the line to read that completely miss out on the ad. Cause Masis may also be a decision making concern and older children. Now the great thing about progressive lenses is that the child will be getting at least some of their ad when they're in down gaze. Regardless of where the frame is sitting and cosmesis isn't a concern. The bad thing is that adaptation is harder. Although I'd safely say that kids do better at this than my adult Progressive Lens. Whereas it's worth considering shorter corridor lens for to help them get down into that ad as soon as possible. They don't need that intermediate zone like a presbyope does. So do consider extended focus or kids specific designs. An example is SLRs is my OPULUX legs Lens, which helps to maximize the use of the ad.
Speaker 2Okay.
Speaker 1Now there's not a lot of new research on progressive or bifocal Lens. My Ip control is everyone's moved on to the exciting contact lens and pharmacological options now. But we still need spectacles in our toolkit for the children who aren't suitable or aren't ready for contact lenses. And if you considering atropine as a first line therapy, your patients may need an ad to help with the accommodation side. Effects of treatment while at his bank concluded that 0.01% atropine only reduces accommodative amplitude by two to three diopters and kids therefore not affecting accommodation. We don't actually know yet what it does to accommodative lag or to the balance between accommodation and vergence. We don't understand those fine or measures of accommodation. So it is something that you should assess and manage.
Speaker 2Okay,
Speaker 1so what else? What might we be doing in the near future for a non contact lens? Suitable Young MIPS, the most exciting new development in spectacle lens technology for my Ip control has recently come out of Hong Kong Polytechnic University. The defocus incorporated multiple segments or dims spectacle lens was recently awarded the Grand Prize, the International Exhibition of inventions in Geneva. This lens is designed to use the simultaneous defocus principles of a contact lens, but to overcome the issue of eye movement behind a spectacle lens. Knowing our contact lens corrections, we can rely on a stable optical profile being cast on the retina once the lens is on because the lens doesn't move around. But we can't do this with a spectacle lens. Well, we couldn't until the dims lens came along, so surrounding a small distance central zone of only 10 millimeters diameter. Beyond that, the Dean's lens is covered 50% with plus three 50 ed lens let's microns in diameter like a fly's eye while the other 50% is the distance power with the appearance of a single vision Lens. When looking away from the optical center, any viewing field of the lens will then be 50% occupied by the distance correction and 50% occupied by the Plus Three 50 add lens let's it's ingenious stuff and its shine about a 60% efficacy in a two year study. Now this lens was developed in collaboration with Hoya who are aiming to have it released in some Asian markets in the second half of 2018 with wider market release likely in 2019 you can read more about the dims Lens in the links below and in the summary text. Personally, I can't wait to see how a lens like this influences binocular vision function, but I'm a big baby node like that.
Speaker 2Okay,
Speaker 1so once you've diagnosed my IPR, the Ip management discussion will pretty much start with spectacles as this is the first correction for a child and a parent who aren't ready for contact lenses. It's always useful to describe the efficacy comparison between spectacles and contact lenses. Firstly, to explain that single vision corrections aren't a first choice. And secondly, to encourage a patient and their parent towards content lens options if they're on the fence, some children will never be ready or suitable for contact lenses and sat in refraction or binocular vision presentations can also lend themselves better to spectacle correction. And you can read more about these cases in the summary and links below. So to wrap it up, if you patient has a significant binocular vision disorder to control, especially he's a foreign accommodative lag. Progressive's in bifocals are an evidence based prescribing choice, which should you pick either a likely to do the job. It depends very much on the child and you chair. If their binocular vision is perfect, though, they're new innovations, like the dims lens might be your first choice in future. Now, summary of the key points from this podcast is below, including a bunch of useful links for further reading. Thanks for listening.