Six year DIMS spectacle lens study shows continued efficacy and no rebound

Paper title: Long-term myopia control effect and safety in children wearing DIMS spectacle lenses for 6 years

Authors: Carly Siu Yin Lam (1,2), Wing Chun Tang (3), Han Yu Zhang (3,4), Paul H Lee (5), Dennis Yan Yin Tse (3,6), Hua Qi (7), Natalia Vlasak (8), Chi Ho To (3,6)

1. Centre for Myopia Research, School of Optometry, The Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong. carly.lam@polyu.edu.hk.
2. Centre for Eye and Vision Research, Sha Tin, Hong Kong. carly.lam@polyu.edu.hk.
3. Centre for Myopia Research, School of Optometry, The Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong.
4. School of Medicine, Nankai University, Tianjin, China.
5. Southampton Clinical Trials Unit, University of Southampton, Southampton, UK.v
6. Centre for Eye and Vision Research, Sha Tin, Hong Kong.
7. Technical Research and Development Department, Hoya Vision Care, Tokyo, Japan.
8. Technical Research and Development Department, Hoya Vision Care, Amsterdam, The Netherlands.

Date: April 2023

Reference: Lam CSY, Tang WC, Zhang HY, Lee PH, Tse DYY, Qi H, Vlasak N, To CH. Long-term myopia control effect and safety in children wearing DIMS spectacle lenses for 6 years. Sci Rep. 2023 Apr 4;13(1):5475. [Link to open access paper]

The Defocus Incorporated multiple Segments (DIMS) spectacle lens has a simultaneous vision design with a clear central zone for correcting the refractive error and a honeycomb patterned mid-periphery containing multiple +3.50D powered segments to impose myopic defocus.

Participants of the previous 3-yr clinical trial were invited to this follow-up study. Previous trials by the same authors examining the efficacy of DIMS lenses found that:

• A myopia slowing effect of 52% for refractive error and 62% for axial elongation was found after 2yrs of DIMS spectacle lens wear, compared to single vision lenses.¹
• A sustained slowing effect for the treatment group after a 3^rd year of wear and a significant decrease in myopia progression and axial elongation for the control group who switched to DIMS treatment lens after 2yrs wearing single vision lenses.²

This study aimed to discover the long-term myopia control effect and safety profile of DIMS spectacle lenses over 6yrs and the effects of discontinuing DIMS lens wear.

During the COVID-19 pandemic where follow-ups were not possible, the participants continued wearing their choice of either DIMS treatment or single vision (SV) lenses. After follow-up intervals could be resumed, there were 90 children in 4 distinct groups with varying wear patterns over the 6yr period:

• Group 1 (n = 36) wore DIMS lenses for the full 6yrs (treatment group)
• Group 2 (n = 14) wore DIMS for 3.5yrs before switching to SV lenses
• Group 3 (n = 22) wore SV lenses for 2yrs before switching to DIMS for 4yrs (the original control group)
• Group 4 (n = 18) wore SV lenses for 2yrs before switching to DIMS lenses for 1.5yrs and then back to SV again

The primary and secondary outcomes were changes in spherical equivalent refraction (SER) measured by cycloplegic auto-refraction and axial length (AL) measured by IOL Master.

Groups 1 and 3 showed less myopic progression and axial elongation than the SV Groups 2 and 4:

• Children in Group 1 (treatment group) showed the least myopia progression and axial elongation for the first 3yrs of wear (-0.52D and 0.32mm, respectively). For years 3 to 6, the changes in SER and AL were not significantly different (-0.40D and 0.28mm, respectively).
• Group 3 (wearing SV lenses for 2yrs then DIMS lenses for 4yrs) showed the least myopic progression and axial lengthening across all groups in the last 2.5yrs of the study.

Groups 2 and 4 showed similar progression and elongation for the last 2.5yrs:

• Group 2 (switched to SV after wearing DIMS for 3.5yrs) experienced changes of 0.48D and 0.31mm, respectively
• Changes for Group 4 (wore SV and then DIMS before wearing SV again) were 0.63D and 0.30mm, respectively
• The changes seen for Groups 2 and 4 did not suggest a rebound effect
• When the rates of myopic progression and axial elongation for these groups were compared before and after wearing DIMS lenses, a flatter slope of progression could be seen for the period of DIMS wear indicating the treatment effect was sustained.

Examinations of visual functions such as best corrected visual acuity, distance and near phoria, stereopsis and amplitude of accommodation found no statistically significant differences, and all were within normal ranges.

Children aged 8-13yrs in this study who wore DIMS spectacle lenses for 6yrs only progressed by -0.92D in their refractive error and 0.60mm in their axial length (-0.15D and 0.10mm per year, respectively):

• There was no significant difference in the slowing effect in the first 3yrs and last 3yrs, and the DIMS lenses were able to provide a consistent treatment effect over this time
• These results are comparable to those from the MiSight (Coopervision) 6-yr soft contact lens trial where myopia progression and axial length growth was slowed by a mean -0.92D and 0.49mm, respectively³

Older children seemed to benefit from a better treatment effect from DIMS lens wear:

• Those who commenced DIMS wear aged 10-13yrs experienced almost no progression or axial elongation
• Although older children tend to display slower progression rates, the results from this study may suggest that DIMS can slow myopia progression in younger children and then maintain little to no progression with continued use in older children.

After stopping wear, the treatment effect was shown to be sustained and there was no evidence of a rebound effect when compared to the initial rates of progression seen in the original 2yr study.

• Again, this is supported by the findings of the MiSight trial which found a continued treatment effect. Any progression measured after discontinuing wear was consistent only with that within the normal range for a child's age, with no rebound effect seen.

Normal visual functions are unaffected both when wearing DIMS lens and after wear is stopped.

Eyecare practitioners can be reassured that the DIMS lens design is a safe and viable option for children and parents wishing to slow myopia progression.

A limitation of this study is a lack of ethnic diversity.

• Only Chinese children were considered in this study. This is understandable when China has a high prevalence of myopia and high myopia: Brien Holden et al found that the prevalence of myopia is more than 2 times higher for those in East Asia than for aged-matched white populations⁴
• However, the MiSight 1 day trial was a multi-ethnic study and found very similar treatment effects over the same period. This may suggest that ethnicity has little impact on the treatment response to myopia control even when it appears to play a part in the prevalence.
• Bullimore and Brennan suggested that regardless of a child's ethnicity, the benefit of any myopia control treatment seems to be the same⁵

Repeated research with multi-ethnic participants will be able to confirm this.

The authors discussed the observation that children aged 8yrs in the study showed the fastest progression rates.

• They suggest relative myopic peripheral refraction (RPR) may impact the treatment efficacy. In the original 2-yr study, younger children with myopic RPR at baseline showed less myopia control effects compared to those who displayed hyperopic RPR at baseline. This remained true throughout the treatment period even with older age.
• If children who already have myopic RPR then receive additional myopic defocus from the DIMS lens, they may be in a situation where there too much myopic defocus at the mid-peripheral retina creates an over-blurred image. If this blur is beyond the threshold of signal detection, myopia control may be less effective for this age group.

Additional research into this field would establish the optimal thresholds for signal detection and perhaps help tailor myopia control treatments according to a child's age and the peripheral refraction values present at baseline.

Title: Long-term myopia control effect and safety in children wearing DIMS spectacle lenses for 6 years

Authors: Carly Siu Yin Lam, Wing Chun Tang, Han Yu Zhang, Paul H Lee, Dennis Yan Yin Tse, Hua Qi, Natalia Vlasak, Chi Ho To

Purpose: This study evaluated the long-term myopia control effect and safety in children wearing Defocus Incorporated Multiple Segments (DIMS) spectacle lenses.

Methods: Participants who completed the 2-year RCT were followed for a total of 6 years; their cycloplegic refractions and axial length were measured. Group 1 (n = 36) wore DIMS spectacles for 6 years; Group 2 (n = 14) wore DIMS lens for the first 3.5 years and SV spectacles afterwards; Group 3 (n = 22) wore SV spectacles in the first 2 years and switched to DIMS; Group 4 (n = 18) wore SV spectacles in the first 2 years, switched to DIMS for 1.5 years and then SV spectacles again.

Results: Group 1 showed no significant differences in myopia progression (- 0.52 ± 0.66 vs. - 0.40 ± 0.72D) and axial elongation (0.32 ± 0.26 vs. 0.28 ± 0.28 mm, both p > 0.05) between the first and the later 3 years. In the last 2.5 years, DIMS lens groups (Groups 1 and 3) had less myopia progression and axial elongation than the single vision groups (Groups 2 and 4). There was no evidence of rebound after stopping the treatment. Post-wear visual functions in all groups were within norms.

Conclusions: The results supported that DIMS lenses provided sustained myopia control without adverse effects over the 6-year study period.

[Link to open access paper]