CW posted a question about spectacle lens options to the Myopia Profile Facebook community. He wondered if bifocals and progressive addition lenses (PAL) were worth the extra cost for parents of myopic children, as the myopia control efficacy is relatively low compared to other options like contact lenses.
Bifocal/progressive addition lens vs. single vision lens
Part of the thought process in deciding on a myopia control strategy involves weighing up the cost against the benefit. In the first instance, the myopia needs to be corrected with either spectacles or contact lenses. When spectacles are the only option available for a myopic child - and this could be for a variety of reasons such as cost, unsuitability or lack of parental interest in contact lenses - the clinician must choose between the following readily accessible options: single vision, progressive addition or bifocal spectacle lenses.
A common rationale is that any of the two are better than a single vision lens (SV). However, CW raises a fair concern as to whether the extra cost of these lenses justify the potentially small myopia control benefit.
Cheng et al showed that prismatic bifocal lenses are effective for patients who have normal binocular vision (BV) status whereas bifocals didn't work as well for children with low accommodative lag.1 On average across multiple studies, bifocal and progressive addition spectacle lenses have reduced myopic progression by 0.25D per year compared to single vision.1-3 While this doesn't sound very exciting in isolation, over the three year study of Cheng et al,1 bifocals with a +1.50 Add reduced final myopia by 0.86D and prismatic bifocals (+1.50 Add with 3 BI in each eye) by 1.01D. To understand more about why the prism was used, read our blog on Progressives, bifocals, binocular vision and more.
As we know, 1D less myopia means 40% less lifelong risk of myopic maculopathy so is worth the interventional efforts. Read more in our blog Why each dioptre matters.
Are bifocals better than progressive addition lenses? Maybe. Progressive addition lenses are likely most valuable for children who show esophoria and accommodative lag in their single vision correction.3
Which add to use for bifocal/progressive additional lens
Studies commonly use +1.50D and +2.00D Adds.4 Leung and co-authors suggested +2.00D as it appears to be more effective than +1.50D in slowing myopia progression.3 In the comments, KG suggests to use the patient’s BV status when assessed in single vision correction to choose the appropriate add to prescribe. For more advice on this, read our blog prescribing adds for accommodative lag and prescribing adds for esophoria. Given that myopes are more likely to have a BV anomaly, this is a good strategy to consider.5,6
Progressive and bifocal spectacle lenses work best for myopia control when considered in view of the patient's binocular vision status - both in terms of efficacy and ensuring visual comfort and acceptance of the lenses. If contact lenses aren't an option, select a progressive addition lens for a child with esophoria and accommodative lag. Select a bifocal or prismatic bifocal in other binocular vision presentations. For more guidance on this, check out our Clinical Decision Trees, where Question 3 includes spectacle lens prescribing in view of binocular vision status.
A small aside: It is worthwhile noting that the way a patient responds to the add in bifocals/PALs isn't necessarily the same as for an add applied in a multifocal soft contact lens (MFCL). The add in bifocals/PALs helps decrease accommodation lag for near work,2 whereas the add in MFCLs has been shown to increase accommodation lag at near,7 likely due to the young eye relaxing their accommodation and using the 'add zone' at near. If you'd like to read more about this, check out Which MFCL - efficacy and function.
Latest spectacle designs
We now have new spectacle lens options for myopia control becoming available, which on early indications show better efficacy than progressive and bifocal spectacle lenses. The first of these is the Defocus Incorporated Multiple segment (DIMS) lens, commercialized by Hoya and already available in some Asian countries, that promisingly appears to provide a level of myopia control similar to contact lens options – even for those patients with normal binocular vision. Read more about this in Spectacle lenses for myopia control: new designs and latest studies.
Take home messages:
- Progressive addition and bifocal spectacle lenses can provide a useful myopia control effect, when correctly applied based on a child's binocular vision status. Bifocals with prismatic correction appear to work best of the standard spectacle lens options, and for most binocular vision presentations.
- Spectacles are usually considered after the patient or parents have turned down contact lens options, however myopia control specific spectacle lens designs are on the horizon, and even available in some countries now.
About Kimberley
Kimberley Ngu is a clinical optometrist from Perth, Australia, with experience in patient education programs, having practiced in both Australia and Singapore.
About Connie
Connie Gan is a clinical optometrist from Kedah, Malaysia, who provides comprehensive vision care for children and runs the myopia management service in her clinical practice.
References
- Cheng D, Woo GC, Drobe B, Schmid KL. Effect of bifocal and prismatic bifocal spectacles on myopia progression in children: three-year results of a randomized clinical trial. JAMA ophthalmology. 2014 Mar 1;132(3):258-64. (link)
- Gwiazda J, Hyman L, Hussein M, Everett D, Norton TT, Kurtz D, Leske MC, Manny R, Marsh-Tootle W, Scheiman M. A randomized clinical trial of progressive addition lenses versus single vision lenses on the progression of myopia in children. Investigative ophthalmology & visual science. 2003 Apr 1;44(4):1492-500. (link)
- Leung JT, Brown B. Progression of myopia in Hong Kong Chinese schoolchildren is slowed by wearing progressive lenses. Optometry and Vision Science. 1999 Jun 1;76(6):346-54. (link)
- Cheng D, Woo GC, Schmid KL. Bifocal lens control of myopic progression in children. Clinical and Experimental Optometry. 2011 Jan;94(1):24-32. (link)
- Gwiazda J, Thorn F, Bauer J, Held R. Myopic children show insufficient accommodative response to blur. Investigative ophthalmology & visual science. 1993 Mar 1;34(3):690-4. (link)
- Gwiazda J, Grice K, Thorn F. Response AC/A ratios are elevated in myopic children. Ophthalmic and Physiological Optics. 1999 Mar;19(2):173-9. (link)
- Gong CR, Troilo D, Richdale K. Accommodation and Phoria in Children Wearing Multifocal Contact Lenses. Optometry and Vision Science. 2017;94:353-360. (link)
