Spectacle Lenses for Myopia Control Part 3: new designs and latest studies

Originally posted April 25, 2020 
Updated July 3, 2023

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.

When judging myopia control efficacy, percentage treatment can be misleading. The percentage can vary based on:

1. The duration of the study (shorter study normally gives a higher percentage)
2. The ethnicity and age of the control group (younger age and Asian ethnicity typically gives faster progression, so can influence the percentage)
3. 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.

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.

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.

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."

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."

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.

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."

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.

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.

SightGlass Vision, a company operating as a joint venture of both CooperVision and EssilorLuxittica, introduced Diffusion Optics Technology (DOT) in an effort to combat childhood myopia. The DOT lenses do not sure lenslets: their paper Control of myopia using diffusion optics spectacle lenses (CYPRESS) describes the lenses as “contain[ing] light scattering centres that disperse light as it passes through the lens, creating lower signal differences between adjacent cones while maintaining excellent visual acuity and functional peripheral vision. Unlike other spectacle lenses for myopia management, DOT lenses allow the wearer to function when looking through the treatment zone: the light scattering features are integrated across the entire lens except for a small clear aperture aligned with the pupillary axis.”

The lenses are based on the contrast theory of myopia aetiology. This entirely different approach is based on studies of genetic forms of myopia, which show cellular defects in cone photoreceptors linked to high myopia. These defects are characterized by some cones having dramatically reduced function, while adjacent cones function more normally. As stated in the randomized controlled trial paper, "This observation suggests that abnormal contrast signalling between neighbouring full and empty cones may stimulate axial elongation." You can read more about this theory in our article The Contrast Theory: A New Approach In Understanding Myopia.

Figure 1 caption from the open-access paper (Rappon 2022): Contrast hypothesis of myopia and development of DOT lens. X-chromosome opsin gene array for a male with high myopia due to the LVAVA haplotype is shown. (A) OPN1LW gene (pink) with LVAVA exon 3 haplotype and OPN1MW gene (green) with MVVVA exon 3 haplotype. The LVAVA haplotype causes exon three to be skipped in pre-mRNA splicing so only about 6% of the mRNA is full length. (B) L (pink) and M (green) cones have dramatically different photopigment OD because of mis-splicing. S cones are blue. (C) Retina signals high contrast even under uniform white light because of OD differences. Activity of L cones (grey) is low, activity of M and S cones (black) is high. We hypothesised that the constitutive contrast signalling due to photopigment OD differences stimulates axial elongation of the eye and causes myopia. (D) The hypothesis led to the development of a novel spectacle lens (DOT lens) that reduces contrast (left lens) compared with a standard of care lens (right). DOT, diffusion optics technology; OD, optical density.

The CYPRESS paper provides 12 month results for the ongoing trial. 256 children aged 6-12 years with myopia of -0.75D to -4.50D were randomised into 3 different lenses: DOT 0.2 lenses with the diffusers spaced 0.365mm, DOT lenses with the diffusers spaced 0.240mm, and single vision lenses. After one year, children in DOT 0.2 lenses had -0.40D less myopia progression than the control; in pattern 2 DOT lenses, children had -0.32D less myopia. This corresponded to a 74% and 59% reduction in myopia progression respectively. The observed difference in AL progression between DOT 0.2 and the control group was 0.15 mm (p<0.0001), while the difference between DOT and the control group was 0.10 mm (p=0.0018), representing a 50% reduction in DOT 0.2 and 33% in DOT.

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.

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.

• Progressives, bifocals and binocular vision

• Back ups and dispensing considerations

• When to prescribe spectacles for myopia control