Correlation in Myopia Progression between right and left eyes in Chinese children with Myopia

Abstract

Purpose: To determine if the rates of progression of myopia correlate between right and left eyes in children with myopia and to determine if there are risk factors associated with asymmetric progression.

Methods: Data from 141 children with myopia (10.5 ±2.0 yrs, -0.50 to -4.0D spherical equivalent), wearing standard spectacle lenses, enrolled in Vision CRC myopia clinical trials from 2007-2012 at Zhongshan Ophthalmic Centre, China and having progression rates for 1 year were considered. Spherical equivalent refractive error using cycloplegic autorefraction and axial length measurements were determined at baseline and 12 months. Rate of progression of myopia was correlated between the eyes using Pearson's correlation. A difference of > ±0.25D in progression rate between eyes was considered to be asymmetric progression. A Chi-square analysis was performed to determine if age, gender, parental myopia, and phoria status played a role in asymmetry.

Results: At baseline, the mean M in right vs left eyes was -2.08±0.70D vs -2.08±0.74D ( r= 0.89, p<0.001). The progression at 12 months was -0.75±0.43D vs -0.73 ±0.43D (r=0.69, p<0.001). Whilst the correlation was substantial, only 56% were within ±0.25D between the eyes. 24.8% of participants had differences of ±0.26 to 0.50D between the eyes, 15.6% had ±0.51 to 0.75D difference and 3.5% had ±0.76 to 1.0D difference. The mean central axial length in right vs left eyes was 24.51±0.81 mm vs 24.49±0.82 (r=0.98,p<0.001). The progression rate at 12 months was 0.35±0.18 mm vs 0.35±0.19 mm (r=0.87,p<0.001). 73% of the participants had differences of ± 0.10 mm. 22.9% of participants had differences of 0.11 to 0.20 mm, 3.6% had differences of 0.21 to 0.30 mm and 0.7% had difference of >0.31 mm. None of the factors i.e. age, gender, parental myopia and near phoria status was found to influence asymmetric progression. Only smaller axial length at baseline was associated with asymmetric progression (p <0.05).

Conclusions: Whilst the correlation between right and left eyes for both mean spherical equivalent and axial length was substantial, 25% or more of the participants had interocular differences that were significant in terms of spherical equivalent refractive error or axial length change. Consideration of interocular asymmetries reduces statistical bias and might offer potential clues to refractive error development and progression.

Keywords: 605 myopia • 464 clinical (human) or epidemiologic studies: risk factor assessment • 465 clinical (human) or epidemiologic studies: systems/equipment/techniques