Myopic children with intermittent exotropia adapt well to Stellest

Paper title: Effect of Spectacle Lenses with Highly Aspherical Lenslets on Binocular Vision and Accommodation in Myopic Children with and without Intermittent Exotropia

Authors: Zhou F (1,2), Li X (1,2), Huang Y (1,2), Li Y (1,2), Zhang J (1,2), Chen H (1,2), Bao J (1,2)

1. Eye Hospital and School of Ophthalmology and Optometry, Wenzhou Medical University, Wenzhou, Zhejiang, China
2. National Clinical Research Center for Ocular Diseases, Wenzhou, Zhejiang, China

Date: Published online October 12, 2022

Reference: Fengchao Z, Xue L, Yingying H, Yuhao L, Jiali Z, Hao C, Jinhua B. Effect of Spectacle Lenses with Highly Aspherical Lenslets on Binocular Vision and Accommodation in Myopic Children with and without Intermittent Exotropia. J Ophthalmol. 2022 Oct 12;2022:9306848.

[Link to open access paper] 

Spectacle lenses with highly aspherical lenslets (HAL) effectively slow myopia progression and axial elongation in myopic children over 2 years.1,2  HAL spectacle lenses have minimal impact on visual function compared to single vision lenses (SVL), at least in healthy myopic children.2,3  However, whether HAL lenses can be safely prescribed to children with binocular vision disorders is also of practical interest. Intermittent exotropia (IXT) is the most common type of strabismus,4  and children with IXT rely heavily on stable binocular function to maintain fusion and ocular alignment. Loss of fusion can result in manifest exotropia. Given the growing adoption of HAL lenses in clinical practice, this study aimed to explore the effect of HAL lenses on binocular vision or accommodation in myopic children with and without IXT.

In this crossover study, 40 myopic Chinese children aged 8-12 years (20 with IXT and 20 visually normal) wore HALs and SVLs in random order. Each test lens was worn for distant viewing for 20 minutes, and binocular vision was assessed afterwards. Stereoacuity, phoria, accommodative facility, fusional vergence, vergence facility, near point of convergence, amplitude of accommodation, and accommodative response were measured.

Key findings were as follows.

• HAL lenses did not significantly affect binocular vision and accommodation in children with or without IXT, except for accommodative microfluctuation (AMF).
• The increase in AMF after wearing HAL lenses was small and similar in IXT (0.04 D) and normal groups (0.05 D).

When prescribing optical interventions for myopia control, a child’s binocular vision status is important context. Binocular vision status can influence our prescribing choices, to ensure children have functional distance and near vision and acceptance of their correction. Binocular vision is altered when wearing contact lenses for myopia control. For example, distance and near exophoric shifts along with improvements in accommodative function can occur after wearing orthokeratology lenses.5 

On the other hand, modern spectacle lens designs for myopia control appear to behave similarly to SVLs. In 2022, Huang et al.2  investigated the short- and long-term effects on HAL lenses on visual acuity, phoria, stereoacuity, and accommodation in a healthy myopic cohort. Across 12 months of follow-up, there was no significant difference between HALs and SVLs apart from larger AMF. In this study, AMF was thought to be a response to peripheral lenslet-induced defocus or early adaptation. Importantly, this did not translate into clinically meaningful changes in accommodative accuracy, amplitude, or binocular vision. This builds on the previous findings by demonstrating that HAL lenses have minimal interactions with binocular vision and accommodation in those with IXT.

Collectively, these suggest that Essilor Stellest lenses are highly unlikely to disrupt binocular vision or accommodation, and can therefore be considered a safe option for myopia management.

This study provides helpful insights, but with a few limitations.

In this study, the short-term outcomes of HAL spectacle lenses in visually normal children align with previous long-term observations. However, with no long-term data for HAL lens wear in children with IXT, the same extrapolation may not necessarily be true.

The findings so far demonstrate that children with mild IXT do not experience any significant impacts to binocular vision while wearing HAL lenses. Short-term wear can often demonstrate the effects of optical disruption. At the same time, a 20-minute adaptation period may have been insufficient for children to show signs of decompensation. A longer period could potentially provide more insight into the responses of children with IXT wearing HAL lenses.

Future research should consider a longitudinal design to determine the long-term effects of HAL lens wear on children with different degrees of IXT. Regardless, children with poorly controlled IXT or at risk of decompensation should be considered for specific solutions, such as vision therapy or surgery.

Purpose: To evaluate the influence of spectacle lenses with highly aspherical lenslets (HAL) on binocular vision and accommodation in myopic children with intermittent exotropia (IXT) and compare the changes after wearing HAL in binocular vision and accommodation in myopic children with or without IXT.

Method: Forty myopic subjects aged 8-12 years were recruited: 20 with IXT and 20 visually normal children. Stereoacuity, phoria, accommodative facility, fusional vergence, vergence facility, near point of convergence, amplitude of accommodation, and accommodative response (AR) were measured by wearing HAL or single vision spectacle lenses (SVL) in a random order after adapting for 20 minutes. Accommodative microfluctuation (AMF) was defined as the standard deviation of AR. Changes in binocular vision and accommodation after wearing HAL were compared between the two groups.

Results: No significant differences were found in binocular vision after wearing HAL versus SVL in either group (all P > 0.05). A greater AMF was found after wearing HAL than after wearing SVL in both groups (0.04 D, 95% confidence interval (CI), 0.03 to 0.05 D, P < 0.001 for the IXT group; 0.05 D, 95% CI, 0.03 to 0.07 D, P < 0.001 for the visually normal group); however, the other accommodation parameters did not change significantly (all P > 0.05). There were no differences in the changes after wearing HAL in any parameter between the two groups (all P > 0.05).

Conclusion: HAL did not significantly change the binocular vision and accommodation for myopic children with or without IXT except for AMF in the short term. 

[Link to open access paper]