I was lecturing recently at the Southern Regional Congress, Australia’s largest optometry conference, run annually in Melbourne. I’d finished my myopia management lecture with a little time to spare for questions, and a colleague asked “when you’re talking about using multifocal soft contact lenses, which designs do you mean? Are you referring to [Coopervision’s] Misight, or the distance centred Biofinity multifocal?”
Good question. Which was I referring to? If you’re fortunate to have access to multiple lens designs, which should you use? The answers depend on consideration of refraction, safety, efficacy and visual function. Some of these considerations are easily answered and some indicate the complexity of myopia management and where the research will likely take us in future. For simplicity, I’ll use the terminology of multifocal soft contact lens (MFSCL) for any lens with more than one optical focus power, including aspherical multifocal (ie. Biofinity) and dual focus (ie. Misight) designs.
This is the easiest and first consideration. If your patient has astigmatism of 0.75 to 1.00D or more, then a spherical MFSCL design may not be suitable. There are no daily disposable, toric multifocals available (that could be asking just a little too much of industry!) and depending on where you are in the world, you may only have one toric MFSFCL available (in Australia, until recently this was the Coopervision Proclear Toric Multifocal), or you may have more (Mark’ennovy’s suite of lenses, available in the UK and Europe and just recently arrived in Australia). You could also consider employing over-specs with the residual toric correction – colleagues have asked me and told me about this prescribing choice – as long as you can guarantee the child will be compliant with wearing the over-specs, otherwise we run the risk of undercorrection, which can promote myopia progression. You’ll then also need to consider range of powers – the Misight, for example, tops out at -6.00 availability. Other lenses, especially those originally designed for presbyopes, have extended ranges into higher minus powers. If you’re after advice on which add to choose for a reusable MFSCL like the Biofinity or Proclear monthly lens, Jeff Walline, the first person to publish on myopia control with these lenses, has put this thoughts together for your reference.
A fascinating clinical innovation is that colleagues are now considering is the Synergeyes Duette Progressive Distance Centred hybrid lens for myopia control. Advantage – any corneal astigmatism should be mostly masked by the rigid lens centre. Disadvantage – the six-monthly replacement schedule. With adds up to +5.00, this is leading to some pondering of MFSCL customisation, and will more add mean more treatment effect – research will tell us more with time.
When it comes to safety, there’s no doubt a daily disposable is the ideal choice, especially to reassure concerned parents. More detail on contact lens safety in children is available here – the punch line being that the risk of microbial keratitis (MK) with a daily disposable is around 2 per 10,000 patient wearing years.1 The risk with a reusable soft lens, such as a silicon hydrogel monthly multifocal, is around 12 per 10,000 patient wearing years,1 and the risk in paediatric OrthoK wear is similar to this.2
I describe this to patients and parents as so: “If you wear these daily disposables for 10,000 years, which you probably won’t… you’ll get 2 eye infections. If you wear the reusable lenses for 10,000 years, which you probably won’t… you’ll get 12 eye infections. The risk is higher, but it’s a pretty small risk either way.” You can also refer patients and parents to our My Kids Vision blog, and the post entitled Are contact lenses safe for kids?
It’s also important to reassure parents that children (aged 8-12) appear to be safer contact lens wearers, according to Mark Bullimore’s important 2017 paper entitled The Safety of Soft Contact Lenses in Children.3 This is likely related to closer supervision of CL handling and wear in children, and less strict behaviours around the same in teens. So while a daily disposable is the ideal choice, the patient’s refraction or the lenses you have available to you may necessitate choosing a reusable multifocal lens. We now have two daily disposable, distance centred multifocal lenses designed for myopia control, and CE marked for use in children in Australasia, the UK, Europe and a handful of other countries – the Coopervision Misight and the Visioneering Technologies NaturalVue.
The bottom line - refraction and safety
If you’re selecting a MFSCL based on safety, a daily disposable is your first choice. If the child is astigmatic, though, you’re likely going to be offering a better overall solution to the child with a toric MFSCL or OrthoK, depending on their suitability and what you have available, and both have similar safety profiles. Part two of this topic will cover efficacy and visual function.