First published April 25, 2020.
Last updated April 9, 2021.
Providing spectacle correction is one of the cornerstones of primary eye care, and myopia controlling spectacles can both correct and control myopia. When it comes to progressive addition spectacle lenses, there is evidence that they may provide a small myopia control benefit only in the presence of a binocular vision disorder - read more in Progressives, Bifocals and binocular vision.
Here we explore the current myopia controlling spectacle lenses which have or are being commercialized, for which peer-reviewed publications are available - their design, presumed mechanism and comparative efficacy.
When it comes to the theories of myopia control mechanisms, the long standing contender is the peripheral defocus theory, whereby the peripheral retina receives myopic defocus as a slow-down or stop signal for eye growth. This has been shown in animal models - Earl Smith III is arguably the world's leading researcher in this area and you can read a summary lecture of his here.
The more recent thought has evolved to the simultaneous myopic retinal defocus theory. Think of this as two planes of focus - one being on the retina to correct myopia, and the other in front of the retina for myopic defocus - which could be anywhere across the retina and not just in the 'periphery'. The latest research on this in animal models, again by Earl Smith and colleagues, can be viewed here.
On the basis of these theories, various myopia control-specific spectacle lenses have been developed and researched. Click on any of the headings for the link to the original research paper. Detail on upcoming clinical trials and designs are also provided below.
Important note on myopia control efficacy
When judging myopia control efficacy, percentage treatment can be misleading. The percentage can vary based on:
- The duration of the study (shorter study normally gives a higher percentage)
- The ethnicity and age of the control group (younger age and Asian ethnicity typically gives faster progression, so can influence the percentage)
- Whether refractive or axial length data is being reported. Axial length can be up to 10 times more accurate than refraction - and often shows a slightly lower percentage - more weight should be given to this data.
Instead of judging efficacy by comparing percentages, compare the absolute effects over the same time period. How much less myopia did the treatment group have? Keep in mind the duration of the study when comparing absolute effects - most of a treatment effect appears to occur in the first year, so treatment effects over two years or longer tend to make comparisons between treatments simpler.
Read more about How to assess the efficacy of myopia control treatments in our review of this key scientific paper on the topic by Brennan et al. 2020.
A 12-month study was conducted, involving 210 Chinese children aged 6 to 16 years, resulting in the lens subsequently commercialized by Zeiss as MyoVision Pro. Participants were allocated to one of four groups;
- Control lens of single vision distance (SV)
- Lens Type I: symmetrical design with a central aperture of 20mm with a peripheral zone equivalent to +1.00D
- Lens Type II: symmetrical design with a central aperture of 14mm with a peripheral zone equivalent to +2.00D
- Lens Type III: asymmetric designs, with a central aperture of 10mm with a peripheral zone equivalent to almost +2.00D.
When all the children are considered, there was no statistically significant change between the control lens and the novel lens. When just the children aged 6-12 years with a parental history of myopia were analyzed, there was a reduced progression of 0.29D when comparing Lens Type III to the control lens.
Presumed myopia control mechanism
This design adheres to the peripheral defocus theory, whereby the peripheral retina receives myopic defocus as a slow-down or stop signal for eye growth.
Efficacy (one year study): Around 20% refractive efficacy in Chinese children aged 6-12 with a family history of myopia, being 0.29D lower refraction, but no difference in axial length change.
In a three-year clinical trial involving 150 Chinese Canadian children aged 8-13 years,11 participants were randomly assigned to:
- Single vision lenses
- Executive bifocal with an Add of +1.50
- Executive bifocal with an Add of +1.50 and 3 Base-In Prism in each eye (6 base-in prism total)
The bifocal lens groups had a significant difference in outcomes compared to the single vision lens, but no significant difference between the two bifocal groups. In three years, myopia progressed -2.06D/0.82mm in SV, -1.25D/0.57mm in bifocals and -1.01D/0.54mm in prismatic bifocals.
The treatment effect was independent of near phoria status. Children with high lags of accommodation (1.01D or more) had a similar treatment effect with both bifocals while children with lower lags (<1.01D) had a greater treatment effect with prismatic bifocals (0.99D less final myopia) than bifocals (0.50D less final myopia).
A key concept with this study is that the use of the BI prism was designed to balance accommodation and vergence systems – not to reduce the response of either system. In a prior study, these authors had tested a combination of adds and BI prism, measuring accommodative lag and exophoric shifts. The +1.50 Add with 3 BI R&L was chosen to ensure that there was no change to either lag or phoria once wearing the bifocal, indicating perhaps a different mechanism of action was at play than altering binocular vision - intrigued? Read more in our Spectacle Lenses for Myopia Control - Progressives, Bifocals and Binocular Vision and When to Prescribe Spectacles for Myopia Control.
Presumed myopia control mechanism
This could be considered as a combination of simultaneous defocus theory and accommodation lag theory. The former is the stronger contender - given that the prismatic bifocals were designed not to alter accommodation or vergence demand. Cheng et al didn't directly investigate this in their clinical trial, but the large zone of ‘add’ in the inferior lens creates a relative peripheral myopic shift on the superior retina, and one (unrelated) study found a relationship between the amount of relative peripheral myopia created by the inferior add zone and the myopia control effect of progressive addition spectacle lenses.
Regarding the accommodation lag theory, the interaction between accommodative lag and success of bifocal type was discussed in the clinical trial paper as indicating that "for children with high lags, reducing the accommodation lags with standard bifocals is adequate to control myopia progression."
Efficacy (three year study): Around 40-50% refractive efficacy and 30-35% axial length efficacy for bifocals and prismatic bifocals respectively in Chinese Canadian children. The absolute effect was around 1D less myopia or 0.3mm less axial elongation over three years. The prismatic bifocals appeared to be slightly more effective, but this was not statistically significant except for children with lower (<1.01D) accommodative lag.
This spectacle lens employs Defocus Incorporated Multiple Segments (DIMS) technology, designed by Hong Kong Polytechnic University, and commercialized by Hoya as MiYOSMART. It is described in the clinical trial paper as "compris[ing] a central optical zone (9 mm in diameter) for correcting distance refractive errors, and an annular multiple focal zone with multiple segments (33 mm in diameter) having a relative positive power (+3.50 D). The diameter of each segment is 1.03 mm. This design simultaneously introduces myopic defocus and provides clear vision for the wearer at all viewing distances. There are multiple foci from myopic defocus at a plane in front of the retina, which would be received as blur images on the retina."
Presumed myopia control mechanism
The description of the multiple zones creating retinal defocus aligns with the theory of creating simultaneous myopic retinal defocus during both distance and near viewing - one plane on the retina due to the single vision zone(s) of the lens, and one plane creating myopic defocus due to the +3.50D defocus lenslets.
In the two year randomized clinical trial, Hong Kong Chinese children aged 8-13 years with myopia -1.00 to -5.00D and no more than 1.50D astigmatism wore either single vision distance (SV) or the DIMS spectacle lens. Cycloplegic autorefraction and axial length were measured. At two years, 160 children completed the trial. Average myopia progression was -0.41D vs -0.85D and 0.21mm vs 0.55mm in DIMS and SV respectively, representing a 50-60% control effect. The paper reported that 21.5% of children who wore DIMS had no myopia progression over two years, compared to only 7% of those who wore SV lenses.
Distance and near acuity in DIMS was similar to SV at around 6/6 or 20/20. While children with strabismus or binocular vision (BV) anomalies were excluded from the study, DIMS showed no influence on near phoria or lag of accommodation compared to SV.
In a newly published three-year study , the children who had already participated in the two-year clinical trial either continued wearing DIMS or switched from the control SV to DIMS. Comparison to an age-matched historical control group showed a myopia control effect in the third year. In the third year, the mean annual myopia progression in the DIMS group was -0.18D and 0.11mm. The control-to-DIMS children showed 0.05D and 0.08mm change, which was not significantly different from the DIMS group. In both groups, more than 80% progressed by less than 0.50D over one year and 5% or less progressed by more than 1D. More than 50% had axial elongation less than 0.1mm.
Efficacy (two year study): Around 50% refractive and 60% axial length efficacy in Hong Kong Chinese children, with an absolute effect of 0.44D lower refraction and 0.34mm less axial elongation in DIMS wearers.
This new innovation in myopia controlling spectacle lens technology uses aspheric lenslets, as described in the clinical trial paper, to "creates a three-dimensional quantity of light in front of the retina, which we call volume of myopic defocus (VoMD) in this paper." Each lenslet is 1.1mm in diameter and "11 concentric rings are formed [across the lens] by contiguous aspherical lenslets."
Presumed myopia control mechanism
This aligns with the theory creating simultaneous myopic retinal defocus during both distance and near viewing, while taking it a step further. The clinical trial paper describes the use of aspheric lenses with a power gradient in animal studies. It states that "Instead of focusing light on two distinct surfaces, as in the case of competing defocus lenses, these aspherical lenses deviate rays of light continuously in a nonlinear manner that creates a three-dimensional quantity of light in front of the retina, which we call volume of myopic defocus (VoMD) in this paper. Greater asphericity, that is, a larger VoMD, reduces lens-induced myopia in chicks.",
The terminology and theory of a 'volume of myopic defocus' as applied to human interventions is new to the field. Consider this a shift in theory from simultaneous defocus in two planes (one being on the retina to correct myopia, and the other in front of the retina for myopic defocus) to a 'volume' of defocus in front of the retina of varying dioptric power.
Figure 1 from Bao et al 2021, with the caption: "Illustration of the study device providing a volume of myopic defocus (VoMD) (white shell) in front of the retina through 11 concentric rings of contiguous lenslets (A=depth of VoMD and B=distance from the retina). The calculations for the lenslets were based on the modified Atchison eye model32 using a retinal shape modified to match the peripheral refraction data of Chinese children.33–35 Spectacle lenses with highly aspherical lenslets (A=0.7 mm and B=1.2 mm), spectacle lenses with slightly aspherical lenslets (A=0.3 mm and B=1.0 mm) (illustrated and authorised by Dr. Damien Paillé from R&D AMERA, Essilor International)."
A recent publication provided one-year results for an ongoing clinical trial. Chinese children aged 8-13 years with myopia of -0.75D to -4.75D were randomized into either single vision, highly aspherical lenslet (HAL) or slightly aspherical lenslet (SAL) spectacle lenses. After one year, 161 children completed the trial and myopia progressed -0.81D/0.36mm in SV, -0.48D/0.25mm in SAL and -0.27D/0.13mm in HAL.
Axial length was stable over the one year study in 28% of the HAL group, 9% of SAL and 0% of SV groups. Distance and near acuity was no different between the groups, being around 6/6 (20/20) at distance and 6/7.5 (20/30) at near. There was no influence of the SAL or HAL lens design on near phoria or lag of accommodation.
Efficacy (one year study): Around a 70% refractive and 60% axial length efficacy for HAL and 40% refractive and 30% axial length efficacy for SAL in Chinese children. This is an absolute effect of 0.54D/0.23mm less myopia for HAL wearers and 0.33D/0.11mm less myopia for SAL wearers.
Coming up in the future
A study is currently recruiting, evaluating the myopia progression control efficacy of defocus incorporated multiple segments (DIMS) lenses and Apollo progressive addition spectacles (PALs) in 6 to 12 year-old children. The patient’s myopia must be between -1.00D and -5.00D. Children will be randomly assigned to either the DIMS lenses or Apollo progressive lenses, and outcomes of refraction and axial length measured over the course of three years.
The Personalized Addition Lenses Clinical Trial (PACT) occurring currently is comparing progressive addition lenses (PALs) with customised ADDs, against standard +2.00D PALs and SVLs. They have enrolled 211 Chinese children 7-12, and are determining the ADD value by the highest ADD that satisfied Sheard’s criterion. This should prove an interesting study as it reflects how PALs would be prescribed under standard orthoptic / optometric principles of binocular vision rather than one single add as investigated in most previous studies. If children had an ADD calculated to be higher than +3.00, they were still allocated +3.00.
Finally, SightGlass Vision, a clinical-stage R&D company focused on myopia solutions, have released some early data from the CYPRESS clinical trial. The study is investigating a novel lens design, aiming to reduce myopia progression. This multi-site study includes 256 children across America and Canada, between -0.75 and -4.00DS from 6 to 10 years of age. They have tested two undisclosed lenses (which clinicaltrials.gov lists as “single vision lens”) against a control single vision lens, with the study planned to continue over 36 months, measuring refraction and axial length outcomes. One year topline data has been presented, with promising outcomes. The company was recently acquired in a joint venture between CooperVision and Essilor. SightGlass promise 24-month interim data analysis soon, so stay tuned.
So are standard spectacle lenses a viable option for my patient?
Yes, progressive addition and bifocal lenses can work - progressives more so if your patient has an accommodative lag. Bifocals may work more effectively, particularly for children with normal binocular vision as described in the study resulting in the Myopilux Max lens, above. There will also always be a place for single vision spectacle lenses, as a back up to other treatments or even a first correction if the parents aren't ready to accept myopia control yet. Read more in When to prescribe spectacles for myopia control.