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Three year follow up clinical study results of the defocus incorporated multiple segments (DIMS) spectacle lens

 Posted on April 27th 2021 by Clare Maher research paper.png

Paper title: Myopia control effect of defocus incorporated multiple segments (DIMS) spectacle lens in Chinese children: results of a 3-year follow-up study

Authors: Carley Sy Lam (1, 2), Wing Chun Tang (3), Paul H Lee (4), Han Yu Zhang (3), Hua Qi (5), Keigo Hasegawa (5), Chi Ho To (3, 2)

  1. Centre for Myopia Research, School of Optometry, The Hong Kong Polytechnic University, Kowloon, Hong Kong
  2. Centre for Eye and Vision Research (CEVR), Hong Kong
  3. Centre for Myopia Research, School of Optometry, The Hong Kong Polytechnic University, Kowloon, Hong Kong
  4. School of Nursing, The Hong Kong Polytechnic University, Kowloon, Hong Kong
  5. Technical Research and Development Department, Hoya Corporation Vision Care Section, Shinjuku-ku, Tokyo, Japan

Date: Mar 2021

Reference: Br J Ophthalmol. 2021; doi: 10.1136/bjophthalmol-2020-317664 [Link to open access paper]

Summary

The defocus incorporated multiple segments (DIMS) spectacle lens was designed by Hong Kong Polytechnic University to control myopia in children and is based on the principle of myopic defocus and simultaneous vision.1 It is a dual focus spectacle lens consisting of a central optical zone (9mm) for correcting distance refractive error, and an annular multiple focal zone with multiple segments of +3.50D (each segment 1.03mm in diameter). This design imposes myopic defocus while providing clear vision for the wearer at all viewing distances.

This study forms the second part of a two-part 3-year study involving DIMS, both conducted by Lam et al. Part 1 of the study was conducted over 2 years to find that the DIMS lens wear slowed childhood adjusted myopia progression significantly (52%) and axial elongation (62%) compared with single vision (SV) spectacles.2 Link to Myopia Profile review of the two year DIMS study results: Defocus Incorporated Multiple Segments (DIMS) spectacle lenses slow myopia progression: a 2-year randomised clinical trial

In the second portion of the study, the children who had already participated in Part 1 either continued wearing DIMS, or switched from the control single vision to DIMS. When compared to an age-matched historical group, both groups experienced a statistically significant reduction in myopia progression and axial length elongation, which was not statistically different from each other.

Clinical relevance

Both DIMS and Control to DIMS groups exhibited a statistically significant reduction in myopia progression

  • In comparison to the historical control group, DIMS resulted in a -0.18D reduction in myopia progression, and 0.08mm reduction in axial elongation
  • In comparison to the historical control group, Control to DIMS resulted in a -0.30D  reduction in myopia progression, and 0.12mm reduction in axial elongation
  • In both groups, at least 80% of the group progressed by <0.50D and over 50% exhibited axial elongation <0.1mm
  • Consequently, DIMS was successful in reducing myopia progression in a group of Hong Kong Chinese children.

Myopia progression and axial elongation of the DIMS group in the third year were similar to those in the first and second year

  • Based on previous research, the greatest treatment effect would be expected in the first year of treatment, and then progressively decline.3 However, this phenomenon was not observed in this study, indicating the treatment of DIMS is sustained over the 3 year period.
  • Further research is required to investigate possible mechanisms for this outcome.

There were no statistically significant differences in myopia progression and axial elongation in the third year between the two groups (p>0.05).

  • While the difference was not statistically different, the Control to DIMS group experienced a greater reduction in myopia and axial length, with a higher percentage of the group.progressing <0.50D. In contrast to the DIMS group, the Control to DIMS group were in their first year of treatment with DIMS lenses. As aforementioned, previous research indicates that the greatest treatment effect is gained in the first year of treatment.3
  • However, as the difference between the groups is not statistically significant, this indicates that DIMS remains effective in slowing myopia progression in older children.

Limitations and future research

There were a number of aspects of the study that acted as limitations

  • Subjects were not randomised
  • The discrepancy in SER between Control to DIMS group and historical group limited the direct comparison of the two groups.
  • The subjects were Hong Kong Chinese children, and hence further research is required to investigate the treatment effect gained in different populations

This study did not examine the rebound effect of DIMS lenses. Further research is required to examine this, as well as determining the optimal age of treatment.

The research project was funded by HOYA, who have commercialised the DIMS lens as MiYOSMART. This acts as a potential conflict of interest and may increase bias.

Full story

Purpose: determine myopia progression in children who continued to wear the DIMS lenses or switched from single vision to DIM lenses for a 1 year period following a 2 year randomized controlled trial. 

Measurment Procedure: SER and axial length were measured at 6-month intervals. Spherical equivalent was measured by cycloplegic auto-refraction, and axial length with an IOL Master. 

Outcomes: There were no statistically significant differences in myopia progression and axial elongation in the third year between the DIMS and Control to DIMS group (p>0.05). As evident in the table below, a higher proportion of the Control to DIMS group progressed <0.50D and exhibited an axial elongation of <0.1mm.


% Progressed <0.5D% Progressed >1D% Axial Elongation <0.1mm
DIMS80552
Control to DIMS87258

DIMS compared to historical control group in SER and AL changes

12 month changes in SER and AL in the historical group were -0.35±0.40D and 0.18±0.13mm respectively. The myopia progression in the DIMS group in the third year was significantly less than in the historical group (mean difference -0.18±0.42D). Axial elongation was also less than in the historical control group (mean difference 0.08±0.15mm).

Control to DIMS compared with historical control group in SER and AL changes

There were no significant differences between the baseline data of the historical group and the Control to DIMS group in terms of age, sex or axial length, however, spherical equivalent was significantly different. This occurred as the historical group was matched to the DIMS group. Consequently, baseline spherical equivalent adjustments were made, which revealed the Control to DIMS group progressed significantly slower than the historical control group (mean difference in SER -0.30±0.42D and axial length of 0.12±0.16mm).

Conclusions: The DIMS spectacle lens slowed myopia progression and axial elongation in children throughout the 3 years of study, providing further evidence that DIMS lenses are an effective myopia control strategy. This myopia control effect was observed in the control-to-DIMS group in the third year, indicating that older children still gain a treatment effect. Further research is required to gain insight into the rebound effect with DIMS wear, and the optimal age of treatment. 

Abstract

Title: Myopia control effect of defocus incorporated multiple segments (DIMS) spectacle lens in Chinese children: results of a 3-year follow-up study

Authors: Carley Sy Lam, Wing Chun Tang, Paul H Lee, Han Yu Zhang, Hua Qi, Keigo Hasegawa, Chi Ho To

Aims: To determine myopia progression in children who continued to wear the defocus incorporated multiple segments (DIMS) lenses or switched from single vision (SV) to DIMS lenses for a 1-year period following a 2-year myopia control trial.

Methods: 128 children participated in this study. The children who had worn DIMS lenses continued to wear DIMS lenses (DIMS group), and children who had worn SV lenses switched to wear DIMS lenses (Control-to-DIMS group). Cycloplegic spherical equivalent refraction (SER) and axial length (AL) were measured at 6-month interval. Historical controls were age matched to the DIMS group at 24 months and used for comparing the third-year changes.

Results: Over 3 years, SER and AL changes in the DIMS group (n=65) were −0.52±0.69D and 0.31±0.26 mm; these changes were not statistically significant over time (repeated measures analysis of variance, p>0.05).

SER (−0.04±0. 38D) and AL (0.08±0.12 mm) changes in the Control-to-DIMS group (n=55) in the third year were less compared with the first (mean difference=0.45 ± 0.30D, 0.21±0.11 mm, p<0.001) and second (0.34±0.30D, 0.12±0.10 mm, p<0.001) years.

Changes in SER and AL in both groups over that period were significantly less than in the historical control group (DIMS vs historical control: mean difference=−0.18±0.42D, p=0.012; 0.08±0.15 mm, p=0.001; Control-to-DIMS versus historical control: adjusted mean differences=−0.30±0.42D, p<0.001; 0.12±0.16 mm, p<0.001).

Conclusions: Myopia control effect was sustained in the third year in children who had used the DIMS spectacles in the previous 2 years and was also shown in the children switching from SV to DIMS lenses.

[Link to open access paper]

Meet the Authors:

About Clare Maher

Clare Maher is a clinical optometrist in Sydney, Australia, and a third year Doctor of Medicine student, with a keen interest in research analysis and scientific writing.

About Ailsa Lane

Ailsa Lane is a contact lens optician based in Kent, England. She is currently completing her Advanced Diploma In Contact Lens Practice with Honours, which has ignited her interest and skills in understanding scientific research and finding its translations to clinical practice.

Read Ailsa's work in the SCIENCE domain of MyopiaProfile.com.

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