Back up corrections, clinical considerations and new designs
There's a little more to think about in the important role spectacle lenses play in myopia management. Even if we prescribe contact lenses, our young myopes are most likely to need a back up spectacle lens option. Children prescribed atropine will need the best spectacle lens prescribed for them to minimise the impact of any side effects. Choosing lenses designed more for kids is important, and we have new options which may work even more like contact lenses - in terms of optics and efficacy - on the horizon.
Back up corrections
Children using atropine as a first line treatment should be monitored for needing an add – while research has described a minimal effect on amplitude of accommodation in lower concentrations,1, 2 we are yet to understand how atropine affects more detailed measures of binocular vision. Consider also any light sensitivity from mydriasis - photochromatic lenses may be indicated.
Children wearing OrthoK may have minimal uncorrected time so may be suitable for single vision distance back up glasses, primarily to manage costs. In practice I find that these back-up spectacles are rarely used by OrthoK wearing children – only to save them taking their lenses on overnight school trips or on occasions where they may be unwell.
Children wearing multifocal soft contact lenses, by comparison, may need a multifocal spectacle lens option depending on their binocular vision function in single vision distance correction. I would take this on a case-by-case basis, applying the principles above in considering both binocular vision correction as well as the best myopia control option. These children ideally should be wearing their contact lenses for at least 8 hours a day,3 and six days a week to get the ideal treatment effect, so frequency of wear and cost may also factor into this decision.
PAL lenses should be selected which have a shorter corridor, to allow the child to access the full add as soon as possible when in downgaze. The immediate accessibility of the full bifocal add in downgaze is appealing, as long as the frame doesn’t slip down and render the add too low! The segment height should be set on the lower lid for maximum utility, while frame fit and adjustments are crucial.
Cosmesis and lens type availability may also factor into the prescribing decision. If you don’t have an E-segment bifocal lens available, will a standard D-segment or curved top do the same job? It will in terms of binocular vision, but it’s hard to say from the myopia control perspective, given what has and hasn’t been studied in research. From a practical perspective, I would suggest that we should be cautious in generalising the research results of one spectacle lens design to all similar designs – the same as for multifocal contact lenses – but that any design of bifocal is better than nothing if the prescribing criteria are met as per Part 1 of this blog.
New spectacle lens technology for myopia control is on the horizon – the award winning Defocus Incorporated Multiple Segments (DIMS) spectacle lens, developed at Hong Kong Polytechnic University, has just been released in Asia. Employing this concept of simultaneous defocus, the DIMS lens has a 10mm clear central optical zone with the distance correction, and then is covered with +3.50 lenslets with regions of the distance correction in between the lenslets. The intended result is that wherever a child looks in the lens, they’ll experience 50% of retinal focus being their distance correction, and 50% of the +3.50 Add. The DIMS lens looks like a single vision lens but could work more like a contact lens because of its innovative design, and has shown contact-lens-level results of 50% refractive control and 60% axial length control in the newly published two year study.4 I’m really looking forward to having this available in practice, but until then, we have loads of options available for our young, first time myopes and children not suitable for contact lenses.