The next generation - DIMS, H.A.L.T., DOT and CARE spectacle lenses for myopia control

Originally posted April 27, 2021
Updated October 16, 2023

The newest myopia controlling spectacles can both correct and control myopia as well as the most effective contact lens options. This is a highly appealing prospect for myopia control practice, as spectacles are likely an easier place to start, and not all children are ready or willing to wear contact lenses.

Spectacle lens myopia control has now moved on from the earliest days of progressive addition and bifocal options to this new generation of myopia controlling specific designs. These are the product of much time and money invested in research and development.

How do Defocus Incorporated Multiple Segments (DIMS), Highly Aspherical Lenslet Target (H.A.L.T.) technology, Diffusion Optics Technology (DOT), Cylindrical Annular Refractive Element (CARE) spectacle lenses and  spectacle lenses work? Here we investigate and compare their design, presumed mechanism and comparative efficacy for myopia control, based on published research.

The DIMS, H.A.L.T., DOT and CARE spectacle lenses take a step beyond the traditional spectacle to behave more like a myopia controlling contact lens. The benefit of a contact lens is that it moves with the eye, so the same optical profile is provided to the central and peripheral retina regardless of the angle of view. This is easy to imagine in the case of a soft multifocal or myopia controlling contact lens, worn on the eye during the day. In the case of orthokeratology, the treatment is 'fixed' through the overnight corneal profile change.

Think of DIMS, H.A.L.T., DOT and CARE as like a single vision lens for myopia correction, with an overlaying 'treatment zone' for myopia control.

• Each has a clear single vision distance zone in the centre of the lens, and a 'background' of single vision correction throughout the periphery of the lens
• There is a surrounding zone of lenslets (DIMS and H.A.L.T.), diffusion microlenses (DOT) or micro-cylinders (CARE) to create a differential myopic defocus across the retina. The lenslet (DIMS and H.A.L.T.) and micro-cylinder spectacles (CARE) have spaces in between the lenslets for the single vision correction
• DIMS and H.A.L.T. Technology lenslet lenses behave like a single vision lens and do not alter accommodation or binocular vision function as does a progressive addition or bifocal spectacle lens. Early data for the DOT lens appears similar. There is no such data for the CARE lens yet.
• Each should be fit like a single vision lens, with careful attention paid to measuring the interpupillary distance and fitting height to ensure the child makes the most of the clear central zone for best acuity.

Perhaps this is why their myopia control efficacy results are seeming to exceed any of the previous spectacle lens solutions, and equaling that of dual focus soft and orthokeratology contact lenses. Let's go further to understand DIMS, H.A.L.T., DOT and CARE spectacle lenses.

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 from 2010, 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, has sought to understand where on the retina (eg. how far into the periphery) and how much defocus difference is required. To learn more about this, start by reading the introduction in this December 2020 paper, here.

The DIMS technology works on the concept of creating simultaneous 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.¹

The H.A.L.T. technology takes this a step further by introducing the concept of a 'volume of myopic defocus'.²  This terminology and theory as applied to human interventions is new to the field, although is cited in the clinical trial paper²  as having a basis in use of aspherical lenses with a power gradient in animal studies. 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 three-dimensional 'volume' of defocus in front of the retina of varying dioptric power.

The DOT lenses are based on an entirely different approach. Instead of employing lenslets to create simultaneous defocus, the SightGlass DOT lens users diffusers to modulate retinal contrast to create a lower signal difference between adjacent cones.³ This is based on the contrast theory of myopia, which hypothesizes that overstimulation of the retina from high contrast is associated with overstimulation of eye growth, thus instigating myopia progression.⁴

The CARE lenses employ micro-cylinders in order to generate high-order aberrations (HOAs) to slow myopia progression. Blur signals on the retina are thought to be involved in normal eye development as it helps to regulate eye growth.⁵ The treatment zone in the CARE lenses are designed to solely create HOAs in the peripheral retina to achieve a myopia control effect. 

Defocus Incorporated Multiple Segments (DIMS) technology was designed by Hong Kong Polytechnic University. 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."¹

Essilor Stellest™ is described as comprising Highly Aspherical Lenslet Target or H.A.L.T. technology in this Press Release. The recent publication of the one year clinical trial paper² describes these spectacle lenses as having "a spherical front surface with 11 concentric rings formed by contiguous aspherical lenslets (diameter of 1.1 mm). The area of the lens without lenslets provides distance correction. The geometry of aspherical lenslets has been calculated to generate a VoMD in front of the retina at any eccentricity, serving as a myopia control signal (figure 1)." The image below is Figure 1 from the open access paper.

The clinical trial paper² describes the use of aspherical lenses with a power gradient in animal studies as a basis for use of the highly aspherical lenslets. 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."

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, (n=161) 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.

A research abstract on the two-year clinical trial data has just been released (n=157), indicating that myopia progressed -1.46D/0.69mm in SV, -1.04D/0.51mm in SAL and -0.66D/0.34mm in HAL. In children who wore their lenses every day for at least 12 hours per day, the absolute myopia control effect compared to SV was 0.99D/0.41mm less myopia in HAL and 0.57D/0.26mm less myopia in SAL.

Diffusion optics technology (DOT) lenses are a little bit different from DIMS and H.A.L.T. in that they do not use lenslets, but diffusers. What are these diffusers? They are thousands of small elements across the lens, shaped as dots that scatter light onto the retina. The small (around 5mm) central section of the lens does not incorporate these dots, providing clear vision and facilitating lens power verification. 

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.⁴ 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."³

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 hypothesized that the constitutive contrast signaling 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.

SightGlass Vision DOT 0.2 lenses have been investigated in a randomized clinical trial of children aged 6 to less than 10 years, with interim 12-month data recently published. The results showed that children wearing the test lens had 0.15mm axial length growth in a year, compared to 0.30mm in the control group, representing a 50% reduction. For children aged 6-7 years, refractive progression was -0.19D in a year in the test lens compared to -0.75D in the control group.³  It is the first data of its type in younger children, which is useful as this age group tends to show fastest myopia progression.⁶ A three-year clinical trial for this lens has been completed but is yet to be published as a full scientific paper.

The Cylindrical Annular Refractive Element (CARE) spectacle lenses were designed by the Wenzhou Medical University.⁵ It is described in the one-year clinical paper as having "a central clear aperture of 9.4 mm in diameter that can provide excellent and stable visual correction, while its peripheral side-vision zone is covered by the annular micro-cylinder array. The annular micro-cylinders are concentrically patterned with a constant radial interval of 1.2 mm. Along the radial direction, the filling factor of the micro-cylinder is 60% in each period. The unoccupied areas between adjacent micro-cylinders share the common base power of the central clear aperture. The micro-cylinder brings an addition of +8.00 D cylinder power to the base power of the occupied areas."

The paper aims to explore the myopia control effect of high-order aberrations using this new lens design. When a flat light wave passes through the treatment zone of the lens, the resultant wave that emerges from the back surface of the lens has a consistent disturbance due to phase retardation from the micro-cylinders. These wave disturbances can be interpreted as HOAs which induce a blurred image on the peripheral retina.⁵

Currently we have two-year randomized controlled trials published for DIMS and for H.A.L.T. technology, both published as full scientific papers. Both have been conducted with Chinese children aged 8-13 years as participants, and with similar baseline characteristics. Let's compare the 6-month and 12-month results as provided in both studies.^1,2

In both studies, a single vision distance (SV) spectacle lens was worn by the control group. From the newer study on the aspherical lenslets, we'll take only the highly aspherical lenslets (HAL) group as they had the larger treatment effect.²

What do you see in those results? Let's compare the control and treatment groups. Keep in mind that we can't do direct statistical tests to see if they are different, so we're looking at the means and standard deviations for similarity or not.

1. Control groups. The single vision wearers in each study had similar axial length progression at 6 and 12 months, albeit perhaps slightly slower for the DOT lens control group, for which 6 month data was not available. This is interesting as the DOT lens study includes a younger population, but was undertaken on an ethnically diverse population across 14 sites in North America, compared to the other three studies undertaken on children in China. Refractive progression in the control group was more variable, as this is a less precise measure.⁷ 
2. Treatment groups. Similar axial length progression at 12 months appears in the DIMS, HAL and DOT lens data. Without direct comparison it cannot be concluded with certainty, but the CARE study progression the treatment group does look to be greater than in the other three studies. When it comes to refractive progression, the story appears to be similar. 

When the control and treatment groups show similar axial length progression, it is likely that the treatment effects of different lens designs can be presumed to be similar. Given that axial length measurement by interferometry techniques is about 10 times more accurate than refraction,⁷ these are the more relevant results.

Once two-year data is available for the DOT 0.2 and CARE lenses, comparisons can be made more robustly. Comparison of percentages also appears to show some differences between the designs, but as recent analysis has explained, percentages must be carefully applied only to the duration of the study and not extrapolated further, as percentage treatment effect can change over time.⁸ So watch this space, for more comparison data.

• Progressives, bifocals and binocular vision

• Back ups and dispensing considerations

• New designs and latest research

• When to prescribe spectacles for myopia control