Purpose: To evaluate the repeatability of a multispectral-based refractor in central and peripheral refraction measurement, and to assess the agreement of such measurements with objective refraction (OR) and subjective refraction (SR) in patients with myopia.Methods: A total of 60 subjects were recruited in this prospective research. Patients were divided into three groups according to the refractive error. Next, the central and peripheral refraction parameters were measured using multispectral refractive tomography (MRT) before and after cycloplegia. In addition, OR and SR measurements were also performed. The intraobserver repeatability was analyzed using within-subject standard deviation (Sw), test–retest repeatability (TRT), and intraclass correlation coefficient (ICC). Agreement was evaluated using Bland-Altman plot and 95% limits of agreement (LoA).Results: The ICC value of central and peripheral refraction were all higher than 0.97 with or without cycloplegia. The peripheral refraction in the nasal, temporal, superior, and inferior quadrants was slightly worse than other parameters, with the largest error interval being 1.43 D. The 95% LoA of the central refraction and OR or SR ranged from −0.89 to 0.88 D and −1.24 to 1.16 D without cycloplegia, respectively, and from −0.80 to 0.42 D and −1.39 to −0.84 D under cycloplegia, respectively.Conclusions: The novel multispectral refraction topography demonstrated good repeatability in central and peripheral refraction. However, the refraction in the nasal, temporal, superior, and inferior quadrants were not as good as that of central and circle peripheral refraction.

Background To assess the current myopia prevalence rate and evaluate the effect of sunshine duration on myopia among primary school students in the north and south of China. Methods This prospective cross-sectional study pooled data from 9171 primary school students (grades from 1 to 6) from four cities in the north and south of China. National Geomatics Center of China (NGCC) and China Meteorological Administration provided data about altitude, latitude, longitude, average annual temperature, and average annual sunshine duration. Non-cycloplegic refraction was recorded, and prevalence rates in primary school students and factors associated with myopia were analyzed. Univariate and multivariate logistic regression models were used to determine the independent association of risk factors of myopia. Results The overall myopia prevalence was 28.0%, from 7.5% to 50.6% for first and sixth grades, respectively. Low, moderate and high myopia significantly increased with school grades from 7.30% to 35.0%, 0.3% to 13.60% and 0.00% to 1.9%, respectively. Multiple regression analysis revealed that longer average cumulative daylight hours were connected to lower myopia prevalence in primary school students (OR, 0.721; 95% CI, [0.593–0.877]; P=0.001), whereas girls and higher grade was independently associated with higher myopia prevalence (girls: β=0.189; OR, 1.208; 95% CI, [1.052–1.387]; P=0.007; higher grade: β=0.502; OR, 1.652; 95% CI, [1.580–1.726]; P<0.001). Conclusion This study demonstrated that myopia was highly prevalent in southern Chinese cities over northern ones, linked to shorter light exposure, higher education level, and female gender. Such findings reinforced the beneficial impact of daylight exposure with a protective role against myopia development.

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Background: To determine the influence of the magnitude of treatment zone decentration on axial length (AL) elongation and to investigate the association between paracentral corneal asymmetry and orthokeratology (OK) lens decentration. Methods: This retrospective study involved 268 subjects (7-14 years) who wore OK lenses for one year. The parameters that reflected the paracentral corneal asymmetry were recorded: corneal toricity; Q value; anterior corneal curvature; and elevation values at the 6-, 7-, and 8-mm chords along the horizontal meridian. The relationships between these data and the amount of treatment zone decentration were analyzed. The relationship of the decentration magnitude and AL elongation was also analyzed. Results: AL elongation was significantly associated with initial age, baseline spherical equivalent, AL, and the decentration magnitude. The subjects with large decentration magnitude showed less AL elongation. The decentration was affected by corneal morphology at the 8-mm chord on the nasal side. In the low curvature group (#41.0D), the decentration magnitude had a stronger correlation with AL elongation than in all subjects. In the high curvature group (.41.0D), the decentration magnitude was no longer correlated with the AL elongation. Conclusion:The decentration of the OK lens effectively slowed the elongation of the eyeball. When the nasal curvature was less than 41.0 D at the 8-mm chord, the magnitude of decentration was predetermined by the flatter curve.