Boosted asphericity improves efficacy of Essilor Stellest design

Paper title: Effect of Increased Power and Asphericity of Highly Aspherical Lenslets on Myopia Control Efficacy: A Contralateral Crossover Study

Authors: Nallour Raveendran R (1), Ong WS (1), Wong YL (1), Zhan SJ (2), Lee CF (2), Lim SY (1), Drobe B (1)

1. R&D, Essilor International, affiliate of EssilorLuxottica, Singapore, Singapore
2. Centre for Quantitative Medicine, Duke-NUS Medical School, National University of Singapore, Singapore, Singapore

Date: Published online November 3, 2025

Reference: Nallour Raveendran R, Ong WS, Wong YL, Zhan SJ, Lee CF, Lim SY, Drobe B. Effect of Increased Power and Asphericity of Highly Aspherical Lenslets on Myopia Control Efficacy: A Contralateral Crossover Study. Transl Vis Sci Technol. 2025 Nov 3;14(11):9.

Link to open access paper

Previous studies have shown that the optical characteristics of lenslets in myopia control spectacle lenses could influence treatment efficacy. Specifically, lenses with highly aspherical lenslets (H.A.L.T. technology, as in Essilor Stellest) have demonstrated superior outcomes compared to those with lower asphericity (slightly aspherical lenslets). These findings suggest a potential dose-response relationship between the optical signal and myopia control efficacy. Building on this, the current study tested whether increasing both the power and asphericity of the lenslets - resulting in the H.A.L.T. MAX design - would further enhance efficacy. The goal was to determine whether this enhanced lenslet design could better slow axial elongation in myopic children.

This was a 12-month randomized, double-masked, contralateral, crossover clinical trial conducted in Singapore. Fifty children aged 6 to 10 years (mean 8.6 years) were enrolled. Participants wore H.A.L.T. MAX lenses in one eye and standard H.A.L.T. lenses in the fellow eye for six months, followed by crossover. At baseline, mean refraction was −1.90 D and mean axial length was 23.98 mm. Axial elongation was the primary outcome.

Key findings were as follows.

• Cumulative 1-year axial elongation was 0.121 mm with H.A.L.T. MAX lenses and 0.228 mm with H.A.L.T. lenses - a difference of 0.107 mm.
• Myopia progression was −0.21 D for H.A.L.T. MAX lenses versus −0.42 D for H.A.L.T. lenses—a difference of 0.21 D.
• Children with faster axial elongation benefitted more from H.A.L.T. MAX lenses.
• Younger children (≤8.5 years) showed a greater difference in axial growth reduction between lenses than older children, but both showed a better effect with the MAX design.
• No significant changes in binocular vision (Worth 4 Dot test) or stereoacuity were observed with either lens design.
• No device-related adverse effects were reported during the study.

H.A.L.T. MAX lenses slowed axial elongation by 0.107 mm more than standard H.A.L.T. (Stellest) lenses over 12 months in a contralateral crossover trial. This enhanced effect appears to result from an increased optical signal, created by boosting the power and asphericity of the lenslets.

For clinicians, this study may support the concept that optical dose matters, at least for this lens design - higher asphericity and power in lenslets can lead to more effective myopia control. Children who showed faster axial elongation with the original Stellest design had greater benefit when switched to H.A.L.T. MAX, suggesting that this lens may be particularly suitable for faster progressors. Similarly, although all children benefited, children under 8.5 years gained greater benefit than older participants, highlighting the potential for earlier intervention with a stronger myopia control signal.

The contralateral design also provides reassurance that significant interocular differences were not induced. Over 12 months, axial growth remained symmetric between eyes despite alternating lens designs. This strengthens the safety profile of using stronger peripheral defocus signals without triggering anisometropia.

This study had several limitations that affect how broadly its results can be interpreted. First, cycloplegia was not used when assessing refractive error, but with axial length as the primary outcome, these results are compelling. Second, the study did not include a washout period between crossover phases, which is a standard element in classical crossover designs. While the authors argue that rebound effects are unlikely with optical treatments, the absence of washout limits certainty about treatment effects in the second phase. Third, although the study spanned 12 months, each lens was worn for only 6 months per eye. This relatively short duration may not capture long-term efficacy or stability of treatment effects.

In addition, the study did not include a control group wearing single vision lenses, which restricts conclusions about the absolute efficacy of either lens design. However, the authors justify this based on ethical concerns around withholding treatment. Lastly, the sample size was modest and may not fully represent broader clinical populations, particularly children outside the 6–10 year age range or those with different ethnic or environmental backgrounds.

These limitations suggest that while the results are promising, further long-term randomized trials—including bilateral designs and diverse populations—are needed to confirm and generalize the findings. 

Purpose: The study aims to evaluate whether the myopia control efficacy of spectacle lenses with Highly Aspherical Lenslet Target (H.A.L.T.) technology could be further improved by a combined increase of power and asphericity of lenslets.

Methods: Fifty Singaporean myopic children aged 6 to 10 years were enrolled in a randomized, contralateral, crossover clinical trial. Two different myopia control spectacle lenses were tested: lenses with H.A.L.T. technology and lenses with maximized H.A.L.T. (H.A.L.T. MAX) technology. One group (N = 25) was assigned to wear H.A.L.T. MAX on the right eye and H.A.L.T. on the left eye, and the other group (N = 25) to wear the opposite combination for 6 months. The combinations were switched for the next 6 months. The primary outcome was the change in axial length (AL).

Results: At baseline, mean (±SD) AL of eyes wearing H.A.L.T. and H.A.L.T. MAX lenses was 23.97 ± 0.84 and 23.99 ± 0.84 mm. After the first 6 months, mean (±SEM) axial elongation in eyes wearing H.A.L.T. and H.A.L.T. MAX lenses was 0.105 ± 0.016 and 0.043 ± 0.016 mm (P < 0.001), respectively. After the crossover, the corresponding mean AL change was 0.123 ± 0.014 and 0.077 ± 0.013 mm (P < 0.001). The differences in AL change between the two lenses were correlated with faster axial elongation with H.A.L.T. lenses in both phases.

Conclusions: Spectacle lenses with H.A.L.T. MAX technology slowed axial elongation more effectively than spectacle lenses with H.A.L.T. technology and might be particularly beneficial for children with faster axial elongation.

Translational Relevance: The relationship between the optical characteristics of lenslets and axial elongation offers a new avenue for developing more effective myopia control lenses.

Link to open access paper