Highly aspherical lenslet spectacles to single vision and back again: a cross-over study

Paper title: Spectacle Lenses With Highly Aspherical Lenslets for Slowing Myopia: A Randomized, Double-Blind, Cross-Over Clinical Trial

Authors: Padmaja Sankaridurg (1,2), Rebecca Weng (1), Huy Tran (1,2,4), Daniel P Spiegel (3), Bjӧrn Drobe (3), Thao Ha (4), Yen H Tran (4), Thomas Naduvilath (1,2)

1. Brien Holden Vision Institute (BHVI), Sydney, Australia
2. School of Optometry and Vision Science, University of New South Wales, Sydney, NSW, Australia
3. Essilor R&D Centre Singapore, Singapore
4. Haiyen Eye Care, Ho Chi Minh City, Vietnam.

Date: Mar 2023

Reference:  Sankaridurg P, Weng R, Tran H, Spiegel DP, Drobe B, Ha T, Tran YH, Naduvilath T. Spectacle Lenses With Highly Aspherical Lenslets for Slowing Myopia: A Randomized, Double-Blind, Cross-Over Clinical Trial: Parts of these data were presented as a poster at the Annual Research in Vision and Ophthalmology meeting, 2022. Am J Ophthalmol. 2023 Mar; 247:18-24. [Link to open access paper]

This randomised, double-blind, cross-over clinical trial investigated how spectacle lenses with highly aspherical lenslets (HAL) may slow myopia progression compared to single vision (SV) control spectacle lenses.

Healthy children (n = 119) aged 7 to 13yrs with spherical equivalent error (SER) between -0.75D to -4.75D and astigmatism of ≤ 1.00DC were randomised to wear either HAL or SV lenses at Haiyen Eye Care, Vietnam.

The HAL novel test lens design features 11 concentric rings of highly aspherical lenslets to provide myopic defocus. These are arranged around the central clear zone containing the distance correction.

The children were asked to wear the lenses for waking hours. The trial comprised 3 stages:

• Stage 1: the children wore either HAL or SV lenses for 6 months
• Stage 2: the lens type was swapped to the opposite lens design and worn for 6 months
• Stage 3: all children wore the HAL design for a final 6 months

The groups were labelled either HSH or SHH to reflect the lens wearing order.

The main outcome measures were 6-month changes in SER and AL. Comparisons of SER and AL changes were made to determine if a myopia rebound effect occurred when swapping from HAL to SV lenses for HSH group.

HAL lenses were found to slow progression over stages 1 and 2.

• In stage 1 there was:
  • 26% reduction in SER (-0.21D with HAL v -0.27D with SV)
  • 54% reduction in AL changes (0.07mm for HAL v 0.14mm for SV).
• In stage 2 there was:
  • 85% reduction in SER (-0.05D for HAL and -0.32D for SV)
  • 71% reduction in AL progression (0.04mm for HAL v 0.17mm for SV)

During stage 3, HSH wearers wearing SV in stage 2 showed renewed reduction in SER progression once swapped back to HAL in stage 3 (-0.33D change in stage 2 and -0.16D in stage 3).

When AL progression rates were compared, there was no difference found between the SHH group wearing SV lenses in stage 1 or the HSH group wearing SV lenses in stage 2 (0.13mm and 0.17mm, respectively). This suggested little rebound effect if HAL lenses were stopped.

Although a myopic shift seen for the SHH group still wearing HAL lenses in stage 3, there was no corresponding axial elongation or difference to the AL progression seen for HSH group in stage 3.

1. This study was able to demonstrate that SV wearers swapping to HAL would experience slower myopia progression. This is reassuring when it reflects children moving from SV lenses to start myopia management.
2. There was also no indication of rebound effect if lens wear was stopped. This was particularly true for those who wore the HAL lenses for 14hrs a day or more, suggesting compliance with full-time wear is important for the full benefit.
3. The HAL lens appears to have given more consistent results for changes in axial length than for refractive error. Where measuring axial length has been suggested as good indicator for monitoring myopia progression,¹ taking regular AL measurements at follow-up appointment would help see the bigger picture of lens performance for myopia control.

The children in the HSH group wore HAL lenses for the last 6mths of the study, while the SHH group wore HAL for the last 12mths.

• A longer study period could evaluate HAL lens performance over a longer time frame, consider rebound effects if lenses were stopped beyond 12mths wear and confirm previous findings of a potential positive dose-dependent relationship between aspherical lens technology and myopia control ^2,3 

There was a myopic shift in SER seen for children wearing HAL lenses during stage 2 and 3 (SHH group)

• The authors suggest this may be due to inadequate cycloplegia or variability in refractive error assessment or due to stage 3 coinciding with COVID lockdown
• However, there was little difference in the AL lengths of both groups in stage 3.

Further research would confirm our understanding of the relationship between AL and SER changes.

Limitations of this study include potential unmasking of HAL wearers due to the lenslet design appearance and COVID lockdown causing dropouts in the final stages which may have affected cross-comparison outcomes.

Title: Spectacle Lenses With Highly Aspherical Lenslets for Slowing Myopia: A Randomized, Double-Blind, Cross-Over Clinical Trial

Authors: Padmaja Sankaridurg, Rebecca Weng, Huy Tran, Daniel P Spiegel, Bjӧrn Drobe, Thao Ha, Yen H Tran, Thomas Naduvilath

Purpose: To evaluate myopia progression with highly aspherical lenslet (HAL) spectacles vs conventional single vision (SV) spectacles.

Methods: A total of 119 Vietnamese children (7-13 years of age, spherical equivalent refractive error [SE] = -0.75 to -4.75D) were randomized to wear either HAL or SV, and after 6 months (stage 1) crossed over to the other lens for another 6 months (stage 2). At the end of stage 2, both groups wore HAL for a further 6 months. In the order that lenses were worn at each stage, group 1 was designated HSH (HAL-SV-HAL) and group 2 SHH (SV- HAL-HAL). The main outcome measures were a com- parison between HAL and SV for change (Δ) in SE and axial length (AL) during each stage; and a comparison of Δ SE/AL with SV between HSH and SHH groups to determine whether myopia rebounded when switched from HAL to SV (HSH group).

Results: Myopia progressed more slowly with HAL than with SV during stages 1 and 2 (SEΔ stage 1: -0.21 vs -0.27D, P = .317, stage 2: -0.05 vs -0.32D, P < .001; ALΔ stage 1: 0.07 vs 0.14 mm, P = .004; stage 2: 0.04 vs 0.17 mm, P < .001). ΔSE/AL with SV was not different between the HSH and SHH groups (ΔSE -0.33 ± 0.27D vs -0.27 ± 0.42D, P = .208; ΔAL 0.17 ± 0.13mm vs 0.13 ± 0.15 mm, P = .092). An average of 14 hours per day of lens wear was reported with both lenses.

Conclusions: In this cross-over trial, intergroup and intragroup comparisons indicate that HAL slows myopia. Children were compliant with lens wear, and data were not suggestive of rebound when patients were switched from HAL to SV.

[Link to open access paper]