The goal of myopia control: eye growth at emmetropic rates?

Paper title: Eye growth pattern of myopic children wearing spectacle lenses with aspherical lenslets compared with non-myopic children

Authors: Yee Ling Wong^1,2, Xue Li^2,3, Yingying Huang^2,3, Yimin Yuan^2,3, Yingying Ye^2,3, Ee Woon Lim^1,2, Adeline Yang^1,2, Daniel Spiegel^1,2, Björn Drobe^1,2, Jinhua Bao^2,3, Hao Chen³

1. R&D Singapore, Essilor International, Singapore, Singapore.
2. Wenzhou Medical University-Essilor International Research Centre (WEIRC), Wenzhou Medical University, Wenzhou, China.
3. National Engineering Research Centre of Ophthalmology and Optometry, Eye Hospital, Wenzhou Medical University, Wenzhou, China.

Date: 15 September 2023

 Reference: Wong YL, Li X, Huang Y, Yuan Y, Ye Y, Lim EW, Yang A, Spiegel D, Drobe B, Bao J, Chen H. Eye growth pattern of myopic children wearing spectacle lenses with aspherical lenslets compared with non-myopic children. Ophthalmic Physiol Opt. 2024 Jan;44(1):206-213.

[Link to research paper]

Understanding emmetropic eye growth in children's eyes is crucial, especially in the context of axial elongation which is typically excessive in progressive myopia. Determining the contribution of physiological growth to axial elongation in myopic eyes is challenging but is essential for assessing the effectiveness of interventions aimed at controlling myopia progression such as the Essilor® Stellest® lenses This study involved 170 myopic children aged 8-13 randomly assigned to wear spectacle lenses with highly aspherical lenslets (HAL), slightly aspherical lenslets (SAL), or single-vision lenses (SVL). Normal eye growth patterns were analyzed using data from 700 non-myopic schoolchildren aged 7-9 from the Wenzhou Medical University-Essilor Progression and Onset of Myopia (WEPrOM) cohort study.

Among non-myopic children aged 7-10 and 11-13 years, the upper limits of slow eye growth (25th percentile) after a 2-year period were 0.20-0.13 mm and 0.08-0.01 mm, respectively, while the upper limits of normal eye growth (75th percentile) were 0.32-0.31 mm and 0.28-0.10 mm, respectively. In the 2-year trial involving 157 children, those wearing highly aspherical lenslets (HAL) full-time (≥12hrs/day) experienced a mean 2-year axial length change of 0.34 mm, compared to 0.51 mm for slightly aspherical lenslets (SAL) and 0.69 mm for single-vision lenses (SVL). The eye growth patterns in approximately 90% of children wearing HAL lenses full-time were similar to or slower than those of non-myopic children over 1- and 2-year periods, compared to only about 10% of children wearing SVL lenses full-time.

The findings suggest that HAL lenses, when worn full-time, may result in eye growth patterns that emulate or are slower than those of non-myopic children. Since axial elongation is the main concern when considering the health implications of myopia,¹ considering axial elongation in the context of normal emmetropic eye growth can provide clearer estimates of efficacy for myopia control interventions.

It is also important to note that these results are achieved when full-time wear (defined as at least 12 hours a day) of the intervention occurs; hence, reinforcing compliance and respect of the wearing time schedule at every consultation is important as well as addressing reasons for non-compliance.  This is one of the first RCTs which has demonstrated the importance of wearing time and its dose response to the treatment’s efficacy.

 HAL lenses or Essilor® Stellest® lenses slow down myopia progression (SER) by 0.99D (67%) and slow down axial elongation by 0.41mm (60%) on average, compared to single vision lenses, when worn at least for 12 hours per day, every day.³ 

This study acknowledged that:

• The study's sample comprised exclusively Chinese children from Wenzhou, China. According to Bullimore et al, ethnicity was unlikely to influence the treatment effect of myopia control modalities.² 
• While the data for WEPrOM was collected during a different period compared to the clinical trial, it is essential to note that emmetropic eye growth measures normal eye growth, which is not known to be impacted by time period.
• The COVID-19 pandemic, which necessitated school closures, could have influenced myopia progression and axial elongation outcomes in the trial.
• Lens wearing duration was subjectively assessed through a questionnaire, with insightful information for clinicians and patients. For future studies, it would be interesting to have a more objective evaluation of the compliance.

 This study contributes significantly to the body of research already behind the Essilor® Stellest® lenses. It has been well established that the Essilor® Stellest® lenses are effective in controlling myopia;³ however, by providing a comparative analysis of eye growth patterns between myopic children using the lenses and their non-myopic peers, it enhances our understanding of how these lenses may influence the normal developmental trajectory of the eye. This comparison is pivotal for assessing the potential of HAL lenses to not only slow myopia progression but also to potentially normalize eye growth patterns, which could have profound implications for the prevention of high myopia and its associated complications later in life. 

Introduction: To evaluate eye growth of children wearing spectacle lenses with highly aspherical lenslets (HAL), slightly aspherical lenslets (SAL) and single-vision lenses (SVL) compared to eye growth patterns in non-myopes in Wenzhou, China.

 Methods: The randomised trial had 170 myopic children (aged 8-13 years) randomly assigned to the HAL, SAL or SVL group. Normal eye growth was examined using 700 non-myopic schoolchildren (aged 7-9 years) in the Wenzhou Medical University-Essilor Progression and Onset of Myopia (WEPrOM) cohort study using logistic function models. Slow, normal and fast eye growth was defined as range of values <25th, 25th-75th and >75th percentiles, respectively.

 Results: The predicted upper limits of slow eye growth (25th percentile) among non-myopes aged 7-10 years and 11-13 years were 0.20-0.13 and 0.08-0.01 mm (after 2-year period; 0.37-0.33 and 0.29-0.14 mm), respectively, while the upper limits of normal eye growth (75th percentile) were 0.32-0.31 and 0.28-0.10 mm (after 2-year period; 0.58-0.55 and 0.50-0.24 mm), respectively. The 2-year trial had 157 children, 96 of whom wore their lenses full time (everyday ≥12 h/day). The mean 2-year axial length change for HAL, SAL and SVL was 0.34, 0.51 and 0.69 mm (0.28, 0.46 and 0.69 mm in full-time wear), respectively. Slow eye growth was found in 35%, 17% and 2% (44%, 29% and 3% in full-time wear); normal eye growth in 35%, 26% and 12% (44%, 32% and 9% in full-time wear) and fast eye growth in 30%, 57% and 86% (12%, 39% and 88% in full-time wear), respectively (p < 0.001).

 Conclusions: The eye growth pattern in approximately 90% wearing HAL full time (compared with about 10% wearing SVL full time) was similar or slower than that of non-myopic children both after 1- and 2-year periods.