Three-year change in refractive error and its risk factors: results from the Shahroud School Children Eye Cohort Study

Longitudinal changes in crystalline lens thickness and power in children aged 6-12 years old

OBJECTIVES

To determine the three-year changes in crystalline lens power (LP) and thickness (LT) in children and their associated factors.

METHODS

Schoolchildren aged 6-12 years living in Shahroud, northeast Iran were examined in 2015 and 2018. The Bennett formula was used to calculate LP. Multiple generalized estimating equations (GEE) analysis was used for data analysis.

RESULTS

Among the 8089 examined eyes, the mean LP in Phase 1 and 2, and the three-year change were 21.61 ± 1.47D, 21.00 ± 1.42D, and -0.61 ± 0.52D, respectively. The GEE model showed that negative shifts in LP were less pronounced with increasing age (β = 0.176; p < 0.001), and were also less noticeable in hyperopes compared to emmetropes (β = 0.120; p < 0.001). The changes in LP decreased when outdoor activity increased among urban residents (β = 0.013; p = 0.039), while it increased in rural area (β = -0.020; p = 0.047). Mean three-year change in LT was 0.002 ± 0.13 mm. Female sex and aging by one year increased the LT by 0.022 mm (P < 0.001). However, LT decreased in 6-8-year-olds, while it increased in 10-12-year-old children, both in a linear fashion. The change in LT was less in myopes than in emmetropes (β = -0.018, P-value = 0.010).

CONCLUSION

LP decreases after three years in 6 to 12-year-old children. LT increases slightly after three years in 6 to 12-year-old children. The changes in LP and LT were associated with the refractive errors, place of residence, age and gender and outdoor activity time.

The association between iris color and refractive errors in children

This study aimed to evaluate the association between iris color and refractive errors in children aged 6-12 years. This cross-sectional study was based on data obtained from the first phase of the Shahroud Schoolchildren Eye Cohort Study. The target population was 6 to12 year-old students living in urban and rural areas. Iris colors were classified by comparing eye colors with close-up images of iris colors. Myopia was defined as a spherical equivalent (SE) ≤ - 0.5 diopter and hyperopia was defined as SE ≥ 2 diopter in cycloplegic refraction. The association of iris color with hyperopia and myopia was investigated by fitting two separate multiple logistic regression models adjusted for place of residence, age, sex, and times for outdoor activity and near work. Among the 5394 participates with the mean age of 9.7 year, the prevalence of myopia and hyperopia was 4.8% and 4.7% respectively. The number and proportion (in parentheses) of amber, light blue, light brown, dark brown, gray, green and hazel iris colors were 19(0.4%), 26(0.5%), 645(12.0%), 4517(83.7%), 4(0.1%), 59(1.1%), and 124(2.3%) respectively. Compared to dark brown, the odds ratios and 95% confidence intervals (in parentheses) of myopia were 4.8(1.2-18.7), 0.8(0.1-5.8), 1.0(0.7-1.5), 0.4(0.1-2.7) and 0.6(0.2-1.8) for amber, light blue, light brown, green and hazel iris colors in multiple logistic regression model. No significant association was observed between iris colors and hyperopia. This study shows that amber iris is significantly associated with higher odds of myopia. These children should be further monitored and examined. More studies with higher sample size in all iris colors are recommended.

Longitudinal Changes in Axial Length and Spherical Equivalent in Children and Adolescents With High Myopia

Purpose

To investigate longitudinal changes in axial length (AL) and spherical equivalent (SE) in children and adolescents with high myopia and to explore associated risk factors.

Methods

This was a longitudinal, observational cohort study of highly myopic participants (aged 7-17 years) to evaluate the mean rates of change in AL and SE. Mixed effects regression models were used to explore the risk factors.

Results

The sample consisted of 293 participants (mean age at the baseline, 13.63 ± 2.66 years; mean AL, 27.03 ± 1.30 mm diopters; mean SE, -8.99 ± 2.30 diopters) who were followed for 7.09 ± 1.64 years. Pathological myopia (PM) was present in 11.95% of the participants at the baseline. Over the follow-up period, the mean AL and SE progression rates were 0.13 mm/y (95% CI, 0.12-0.14) and -0.36 diopters/y (95% CI, -0.39 to -0.34). The multivariate analysis showed that the AL elongation and myopic SE progression decreased significantly after age 11 (β = -0.080, P < 0.001; β = 0.146, P < 0.001), increased with a greater baseline SE (β = -0.006, P = 0.014; β = 0.017, P = 0.005), and accelerated in children and adolescents who had PM at the baseline (β = 0.043, P = 0.011; β = -0.097, P = 0.025).

Conclusions

A significant association was found between acceleration of AL elongation and myopic SE progression among the children and adolescents with age, especially those younger than 11 years, and the presence of PM.

Progression and incidence of myopia among schoolchildren in the post-COVID-19 pandemic period: a prospective cohort study in Shantou, China

OBJECTIVES

To determine the progression and incidence of myopia in Chinese schoolchildren in the post-COVID-19 pandemic period in Shantou, China.

DESIGN

Prospective cohort study.

SETTING

Shantou Myopia Study, China.

PARTICIPANTS

1-year follow-up data were available for 621 881 schoolchildren (301 999 females). Data on spherical equivalent refraction (SER) were collected.

PRIMARY AND SECONDARY OUTCOME MEASURES

The primary outcomes were myopia progression and incidence. Myopia progression is defined as a change of SER towards the negative direction in the follow-up visit. Incidence is defined as the proportion of schoolchildren who were not myopic but developed myopia in the follow-up study. Age, sex and SER at baseline were evaluated as associated factors for myopia burden, which were defined as the secondary outcomes.

RESULTS

Mean progression of SER was -0.35±0.97 D for the population (ranging from -0.06 D at 18 years of age to -0.46 D at 11 years of age), with a rapid myopic progression for students at the age of 10-12 years (-0.50 D in girls and -0.44 D in boys). A myopic shift greater than -0.50 D/year occurred in 256 299 eyes (41.21%). Myopic progression in refraction was associated with the 10-12 years age groups (OR 1.42; 95% CI 1.39 to 1.45, p<0.001), female sex (OR 1.09; 95% CI 1.08 to 1.10, p<0.001) and higher refractive errors at baseline (OR>1.00, p<0.001). The annual incidence of myopia among schoolchildren was 24.85%, with an incidence of 26.69% in girls and 23.02% in boys.

CONCLUSIONS

Our study revealed an annual myopia progression of -0.35 D and an incidence of 24.85% among schoolchildren in the post-COVID-19 pandemic period. Myopia progressed rapidly at 10-12 years of age, with -0.50 D in girls and -0.44 D in boys. The incidence was higher for children aged 10-11 years and for girls.

Baseline Refractive Error, Habitual Accommodative Tone, and Its Association With Myopia in Children: The Lhasa Childhood Eye Study

PURPOSE

The purpose of this study was to describe the baseline refractive error, habitual accommodative tone (HAT) in Tibetan children and its longitudinal association with incident myopia and myopia progression.

METHODS

This was a prospective cohort study. From 7 elementary schools, 1440 children with mean age of 6.83 ± 0.46 years were included with full noncycloplegic and cycloplegic refraction data at baseline, 1-year and 2-year follow-up in the Lhasa Childhood Eye Study. Noncycloplegic and cycloplegic automated refraction were performed at baseline and annually over the next 2 years. HAT was measured as the difference in spherical equivalent (DSE) between noncycloplegic and cycloplegic refraction.

RESULTS

The mean HAT decreased from a baseline value of 0.92 ± 0.82 diopters (D) to 0.55 ± 0.65 D, P < 0.0001 at 2 years. In multivariable logistic regression models, only baseline spherical equivalent (SE; P < 0.0001) was significantly (negatively) associated with 1- and 2-year incident myopia. Among 1386 children without myopia at baseline, 271 developed myopia over 2 years. For hyperopic children, baseline HAT was significantly associated with the incidence of myopia over 2 years (odds ratio [OR] = 0.43, P < 0.001), and the incidence of myopia was significantly lower with baseline HAT ≥0.5 D, compared to children <0.5 D. For 54 (3.75%) children who were myopic at baseline, SE was significant positively associated with myopic progression in univariable (P = 0.03) and multivariable general mixed linear regression analysis (P = 0.03).

CONCLUSIONS

Baseline SE was an independent influencing factor for the incidence of myopia and its progression. The incidence of myopia was significantly higher with lower baseline HAT among hyperopic children, indicating that lower HAT was potentially associated with myopic development.