How effective is spectacle correction for myopic anisometropia?

Paper title: Spectacle correction may affect refractive progression in children with unilateral myopic anisometropia: A retrospective study

Authors: Wang, Shuai (1,2); Zhang, Beilei (1,2); Liu, Qiming (1,2); Zhou, Fan (1,2); Chen, Yunyun (1,2); Xu, Jingjing (1,2)

1. State Key Laboratory of Ophthalmology, Optometry and Vision Science, Eye Hospital, Wenzhou Medical University, Wenzhou, China.
2. National Engineering Research Centre of Ophthalmology and Optometry, Eye Hospital, Wenzhou Medical University, Wenzhou, China.

Date: Nov 2024

References: Wang S, Zhang B, Liu Q, Zhou F, Chen Y, Xu J. Spectacle correction may affect refractive progression in children with unilateral myopic anisometropia: A retrospective study. Ophthalmic Physiol Opt. 2024 Nov;44(7):1392-1397

[Link to abstract]

A significant difference in refraction of 1D or more between the two eyes (anisometropia), can result in unequal retinal image sizes (aniseikonia) or binocular vision issues such as strabismus and amblyopia.

Children with unilateral myopic anisometropia (UMA), with one (often emmetropic) eye and one myopic eye, may experience increasing myopic progression with age. Monocular orthokeratology in UMA has been found to slow axial elongation in the myopic eye in some studies, although some progression in the non-myopic eyes was also seen.^1-4

This retrospective study investigated the impact of spectacle correction on refractive progression in children with unilateral myopic anisometropia (UMA).

The participants were children (n = 153) aged 8 to 12yrs with UMA who were outpatients of the Affiliated Eye Hospital of Wenzhou Medical University. The inclusion criteria were for spherical equivalent refraction (SER) of myopic eyes between -0.75 to -4D, from +1 to -0.25D for non-myopic eyes, astigmatism of no more than 1.50D, anisometropic difference of at least 1D and data for at least 3 non-cycloplegic subjective SER and AL measurements over 1yr.

The participants were divided into 2 groups: uncorrected group (UC, n = 47) who received no spectacle correction, and spectacle group (SP, n = 106) who wore spectacles. Main outcome measures were changes and increases in SER and AL and anisometropia and intraocular AL difference over 1yr follow-up period.

• The participants had a mean AL difference between the two eyes of 0.77 and 0.55mm, anisometropia of 1.71 and 1.34D and mean ages of 10.1 and 9.6yrs in the SP and UC groups, respectively.
• At 1yr, the SP group showed similar axial elongation (~0.3mm) in both myopic and emmetropic eyes, with no change in the level of anisometropia. 
• The UC group showed 0.43mm growth in the myopic eye and only 0.15mm growth in the ememtropic eye over 1 year, reflecting an increase in anisometropia from 1.34D up to 2.01D.

When the groups were compared, uncorrected myopic eyes (UC group) were seen to elongate faster than those in the spectacle (SP) group. However, emmetropic eyes in the SP group had faster AL change than those in the UC group, although the refractive difference was less than 0.25D.

The SP sub-group had faster AL and SER changes in the myopic eyes prior to commencing spectacle wear, which slowed after wear. Although SER increased for the emmetropic eyes after wearing spectacles, it was not significantly different to values prior to wear.

This study found that uncorrected myopic eyes progressed faster and this progression slowed once spectacles were prescribed.

• This suggests that early diagnosis of UMA is essential and that the decision to use spectacles for children with UMA should form part of an individualised treatment plan which is guided by axial length and refractive change monitoring
• These results confirm those found by another retrospective study where myopic eyes progressed faster than emmetropic eyes in children with UMA and similar to the rate of progression in non-anisometropic myopic eyes.⁵

Children with unilateral myopic anisometropia may experience slower axial elongation and refractive changes in their myopic eye and become less anisometropic if spectacles are prescribed. Ultimately, reducing their anisometropia will reduce the risk of binocular vision problems and amblyopia

The non-myopic eyes in this study showed increased myopic progression with spectacle wear, although the difference in refraction was less than 0.25D. When compared to the almost 0.75D increase in anisometropia from uncorrection, though, these risks may be balanced. Close monitoring would be advised.

• This study followed the participants retrospectively for 1yr. This limits our understanding of long-term myopia progression in either eye for both corrected and uncorrected UMA.
• The children were aged 8-12yrs and from China. This may mean the results cannot be generalised to other age groups or ethnicities which may have different SER and AL progression rates.
• Spectacle wear was assessed in this study. Further research could investigate how effective myopia control interventions such as atropine or orthokeratology could be for children with UMA, and if their use would be monocular or binocular.
• When discussing binocular function and accommodative demand, the authors make reference to their unpublished data which showed accommodative lag became similar between the two eyes after spectacle correction. Further research could examine visual functions such as these to assess the role they play in myopia development in UMA

Limitations to this study include using a retrospective design, limited control over confounding factors such as outdoor time or screen time, and a small sample size for the sub-group analysis. Further studies using randomised trial designs and which examine the role of binocular function would help expand on this study’s findings. Longer follow-ups would help assess long-term effects.

Title: Spectacle correction may affect refractive progression in children with unilateral myopic anisometropia: A retrospective study

Authors: Shuai Wang, Beilei Zhang, Qiming Liu, Fan Zhou, Yunyun Chen, Jingjing Xu

Purpose: To investigate the effect of spectacle correction on refractive progression in children with unilateral myopic anisometropia (UMA).

 Methods: In this retrospective study, 153 children with UMA (aged 8–12 years) were recruited and classified into an uncorrected (UC) group (n = 47) and a spectacle (SP) group (n = 106). The spherical equivalent refraction (SER) of the myopic eyes ranged from −0.75 to −4.00 D; the SER of the emmetropic eyes ranged from +1.00 to −0.25 D; anisometropia was ≥1.00 D and the follow-up duration was 1 year. Nineteen subjects from the SP group with follow-up records spanning at least 6 months before and after wearing spectacles were selected as a subgroup. Changes in the SER and axial length (AL), the degree of anisometropia and interocular AL differences of the two groups and the subgroup were analysed.

Results: During the 1-year follow-up period, AL and SER changes in myopic eyes were significantly greater than those in emmetropic eyes in the UC group (p < 0.001). For the UC group, the degree of anisometropia and AL change increased (all p < 0.001). For the SP group, there were no significant differences in the degree of anisometropia or AL change (all p > 0.05). When comparing the groups, AL elongation of the myopic eyes in the UC group occurred significantly faster than in the SP group (p = 0.02), and AL elongation for the emmetropic eyes in the UC group occurred significantly slower than in the SP group (p = 0.04). For the subgroup, the AL and SER changes in the myopic eyes 6 months before wearing spectacles occurred significantly faster than those after correction (p < 0.001).

Conclusions: Spectacle correction could prevent increased anisometropia in uncorrected children with UMA by slowing myopia progression in the myopic eyes and accelerating the myopic shift in the contralateral eye.

[Link to abstract]