Paper title: Defocus Incorporated Multiple Segments (DIMS) spectacle lenses slow myopia progression: a 2-year randomised clinical trial
Authors: Carly Siu Yin Lam (1), Wing Chun Tang (1), Dennis Yan-yin Tse (1), Roger Pak Kin Lee (1), Rachel Ka Man Chun (1), Keigo Hasegawa (2), Hua Qi (2), Takashi Hatanaka (2), Chi Ho To (1)
- Centre for Myopia Research, School of Optometry, The Hong Kong Polytechnic University, Hung Hom, Hong Kong
- Hoya Corporation, Tokyo, Japan
Date: March 2020
Reference: Br J Ophthalmol.
The DIMS (Defocus Incorporated Multiple Segments) lens was developed by Hong Kong Polytechnic University with the aim of inhibiting myopia progression in children.
The lens design consists of a 9mm central zone to provide the distance refractive correction with a surrounding 33mm width annulus made of multiple defocus segments. Each of these segments has +3.50D power and are 1.03mm in diameter. The multiple myopic defocus images from the segments are presented alongside clear distance vision for the wearer.
This study aimed to establish the influence the lenses had on children’s ocular development by randomly allocating DIMS lenses and single vision (SV) lenses to Chinese children, before assessing their myopia progression and axial length growth after two years daily use.
The authors found the children who wore the DIMS lenses had 52% less myopia progression and 62% slower axial length growth compared with those who wore the SV lenses.
The conclusion was that the induced simultaneous vision from the multiple segments was effective in slowing myopia progression.
The DIMS lenses provided a significant reduction of 52% slower refractive change and 62% slower axial length elongation over 2yrs compared to SV lenses
- The authors found this was a comparable efficacy to that of other current myopia management options, where Orthokeratology gave approx. 60%,1,2 soft bifocal contact lenses approx. 50-60%1,3,4 and prismatic bifocal spectacle lenses approx. 50%5
- Eyecare practitioners can use DIMS lenses as an effective spectacle lens option for managing myopia
Visually, the DIMS design provided equivalent vision for distance and near to the SV lenses
- There were few adaptation issues, other than slight peripheral blurring initially which became less noticeable with wear
- This information can be discussed with children and parents when considering DIMS spectacles
Older children seemed to benefit more than younger children from wearing DIMS lenses during the study
- Age was associated with a greater slowing effect for 10-13yr olds than for those aged 8-9yrs olds
- Most of the children who showed continuing progression despite wearing the treatment DIMS lenses were aged 8-9yrs
- The authors suggested this may be due to differing retinal contours with age giving higher peripheral hyperopia, therefore minimising the myopic defocus treatment effect in younger children
- Knowing this can help practitioners decide which children may benefit most from being dispensed DIMS lenses. DIMS could present a myopia-correction-and-control option for older teens and adults not willing or suitable for contact lenses.
Limitations and future research
The study only included children with myopia within the range of -1.00 to-5.00D
- There is therefore no data, at present, on the expected results for higher myopia correction
- Future studies extending this range could provide insights as to the slowing effect possible
- They could also reveal the ideal wear time (in years) to maximise the effect from the lens design and the point at which no extra benefit can be achieved
The children participating in the study were aged between 8 and 13yrs old
- The older children (10-13yr olds) experienced improved results from the myopic defocus compared to the younger children
- It is uncertain if the DIMS lenses could maintain efficacy with children over 13yrs
- There was continued progression seen with 13% of the DIMS wearing children, with most of these being younger (8-9yrs old)
- When Cheng et al5 examined their results from using prismatic bifocals for myopia control, they found a similar discrepancy and that a child’s age, initial myopic error and parents myopic status influenced the outcome
- With the DIMS lens, the authors only found a child’s age was associated with the performance outcome
- Additional research into age-related changes of the peripheral refraction and peripheral retinal shape and the subsequent reception of myopic defocus within the eye could help confirm the ideal age range for using DIMS lenses
The authors conceded that as this study featured only Hong Kong Chinese children, the results cannot be assumed to be the same for children of other ethnicities
- Repeating the clinical trial in other countries would confirm the effectiveness of the DIMS lens where different patterns of myopia incidence and progression will exist
The trial was masked and randomised and therefore the children and their parents ideally would be unaware of having received the DIMS treatment lens or the SV lens
- However it is possible that if the lenses were examined, the segments could be visible
- Although this wouldn’t affect the objectively measured results, it does suggest some participants may have been aware they had received the treatment option and were therefore ‘unmasked’ before the trial ended
The results from this study differ from other research focussed on the DIMS lens design.
- The authors concluded that the DIMS lens did not reduce BCVA. However, a recent optical analysis by Jaskulski et al reported that the optics of the DIMS lens reduces contrast at high spatial frequencies compared to a dual-focus contact lens.6
- Consequently, further research is required into the impact of DIMS on quality of vision.
This was the first phase of Lam et al’s study into the performance of the DIMS lenses
- At the time of it being published, the second phase had yet to be completed.
- The aim was to further examine the continued use of DIMS lenses for the children already wearing them, as well as assessing the impact of introducing the lenses to those who had used the SV lenses.
This second phase of the study has since been studied and reviewed on Myopia Profile: Myopia control effect of defocus incorporated multiple segments (DIMS) spectacle lens in Chinese children: results of a 3-year follow-up study.
The aim of this study was to explore the extent to which Defocus Incorporated Multiple Segment (DIMS) design spectacle lens could slow myopia progression and axial length elongation in Chinese children.
Lam et al conducted a randomised, masked prospective study of 183 Hong Kong Chinese schoolchildren aged 8-13yrs old between August 2014 and July 2017. The children were randomly assigned either the DIMS lens giving myopic defocus induced by multiple plus-powered segments or a single vision (SV) lens.
The inclusion criteria included ensuring the children’s refractive error ranged between -1.00 and -5.00D, less than 1.50D of astigmatism, and that no previous myopia control had been undertaken.
The children’s refractive error and axial length were measured at baseline and afterwards at six-month intervals during the study. A masked investigator used cycloplegic examination and an open-field auto-refractor (Shin-Nippon NVision-K5001) to record the refractive error and axial length was measured using IOLMaster (Carl Zeiss). Other parameters such as distance and near acuity, near phoria and accommodation were also noted at each visit.
The children were randomly selected to receive either the DIMS treatment lens (93 children) or SV lenses (90 children) and were unaware of which lens they received. They were asked to wear the spectacles for full-time use, with the wearing times and comfort of using the lenses confirmed with follow-up phone calls and questionnaires.
The change in myopia progression was calculated as the difference between the mean cycloplegic refraction results at baseline and the final results after 2 years.
The change in axial length was the difference between the mean axial length data at baseline and the final values after 2 years.
How effective the DIMS lens is in reducing myopia was calculated by dividing the differences in the myopia progression and axial length between the DIMS and SV groups and then multiplying by 100 to give a percentage efficacy.
Out of the original 183 children, 160 completed the trial wearing either DIMS (79 children) or SV lenses (81 children).
The baseline mean myopia refraction was -2.93 +/- 1.04D for the DIMS group and -2.70 +/- 0.98D for the SV group. The mean baseline axial length was 24.85 +/- 1.59mm for the DIMS group and 24.72 +/- 1.30mm for the SV group.
Both groups wore the lenses for an average time of over 15hrs daily.
Generalised estimating equations were used to account for missing data from 23 of the participants who dropped out of the study after the baseline data had been collected. The information collected from all of the subjects was adjusted for influences from covariates such as gender, age, time spent on near work and parental myopia. It was found that their allocated group, time and age had an effect on the extent of the changes seen for myopia progression and axial length.
After the data was adjusted to allow for these covariates, Pearson correlation analysis found that changes in refraction were significantly correlated with the children’s ages in the DIMS group, where older children experience slightly slower progression changes. There was no significant change found in the SV lens group.
Changes in myopic refractive error
- The mean progression found for the children wearing the DIMS lenses was -0.41 +/- 0.06D, compared to -0.85D +/- 0.08D for the SV lens group.
- The DIMS lens was shown to provide 52% less progression of myopic error where the mean difference was -0.44 +/- 0.09D.
- From the SV group, there were 7% of children who showed no myopia progression over the 2year study, whereas 21.5% of the children wearing DIMS lenses experienced no progression over the same time.
Changes in axial length
- The mean axial length growth for the DIMS wearers was 0.21 +/- 0.02mm. The SV lens wearers showed 0.55 +/- 0.02mm elongation in comparison.
- The DIMS lens was shown to give 62% slower axial length growth compared to wearing a single vision lens with a mean difference of 0.34 +/- 0.03mm
- All of the children wearing SV lenses showed axial length elongation after 2 years, whereas 14% of the DIMS wearing group exhibited no elongation.
The DIMS lens design was shown to be effective in slowing progression of myopic refraction and axial length elongation when worn daily for two years, compared to single vision lenses.
Children wearing the DIMS lenses had shown a significant reduction in the progression in their myopia progression as well as their axial length growth, suggesting that the induced myopic defocus from the lens segments during wear is responsible for the results.
Due to its non-invasive nature, DIMS lens provides an alternative for eye care practitioners to offer to children to manage myopia progression.
Further research could confirm the optimum age and refractive error range for the full benefit.
Title: Defocus Incorporated Multiple Segments (DIMS) spectacle lenses slow myopia progression: a 2-year randomised clinical trial
Authors: Carly Siu Yin Lam, Wing Chun Tang, Dennis Yan-yin Tse, Roger Pak Kin Lee, Rachel Ka Man Chun, Keigo Hasegawa, Hua Qi, Takashi Hatanaka, Chi Ho To
Aim: To determine if ‘Defocus Incorporated Multiple Segments’ (DIMS) spectacle lenses slow childhood myopia progression.
Methods: A 2-year double-masked randomised controlled trial was carried out in 183 Chinese children aged 8–13 years, with myopia between −1.00 and −5.00 D and astigmatism ≤1.50 D. Children were randomly assigned to wear DIMS (n=93) or single vision (SV) spectacle lenses (n=90). DIMS lens incorporated multiple segments with myopic defocus of +3.50 D. Refractive error (cycloplegic autorefraction) and axial length were measured at 6month intervals.
Results: 160 children completed the study, n=79 in the DIMS group and n=81 in the SV group. Average (SE) myopic progressions over 2 years were −0.41±0.06 D in the DIMS group and −0.85±0.08 D in the SV group. Mean (SE) axial elongation was 0.21±0.02 mm and 0.55±0.02 mm in the DIMS and SV groups, respectively. Myopia progressed 52% more slowly for children in the DIMS group compared with those in the SV group (mean difference −0.44±0.09 D, 95% CI −0.73 to −0.37, p<0.0001). Likewise, children in the DIMS group had less axial elongation by 62% than those in the SV group (mean difference 0.34±0.04 mm, 95% CI 0.22 to 0.37, p<0.0001). 21.5% children who wore DIMS lenses had no myopia progression over 2 years, but only 7.4% for those who wore SV lenses.
Conclusions: Daily wear of the DIMS lens significantly retarded myopia progression and axial elongation in myopic children. Our results demonstrated simultaneous clear vision with constant myopic defocus can slow myopia progression.
Clare Maher is a clinical optometrist in Sydney, Australia, and a second year Doctor of Medicine student, with a keen interest in research analysis and scientific writing.
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.
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