The aim of this study was to investigate the characteristics of refractive development at different months of age and effects of blue light exposure on it in infants during the neonatal period.

A retrospective clinical study was conducted on 82 infants (164 eyes) received phototherapy during the neonatal period and 64 healthy infants (128 eyes) born in Department of Pediatrics, Peking University Third Hospital from January 2016 to June 2020. Among of them, there were 86 males (172 eyes) and 60 females (120 eyes) with an average age of (31.1±6.7) months (ranged from 6 to 36 months). The infants were divided into phototherapy group and control groups, according to whether or not they had received phototherapy during the neonatal period. Binocular non-cycloplegic refraction of infants at 6, 12, 18 and 24 months old was examined and recorded, including spherical equivalent refraction (SER), spherical refraction, astigmatism, astigmatism axis.The age was expressed as ±s after normality test and compared by independent sample t test between groups; the gender was countable data, described as cases and perentage, and compared by Chi-square test. After normality testing, SER, spherical refraction, astigmatism, and astigmatism axis were skewed distribution in different time, described as median and interquartile range, and compared by Mann-Whitney U test rank sum test. The effect of age and groups on refractive development was analyed by mixed effect model.

At 6 months, SER, spherical refraction, astigmatism, and astigmatism axis of infants in the phototherapy group were 0.17 (1.96)D, 1.0 (2.0)D, -1.25 (1.0)D and 75.5 (155.3), respectively; while those of the control group were -0.13 (2.63)D, 0.5 (2.0)D, -1.20 (1.0)D and 93.5 (138.0), with non-significant difference between two groups (Z=-0.89, -0.939, -1.721, -0.555; P> 0.05). At 12 months, SER, spherical refraction, astigmatism, and astigmatism axis in the phototherapy group were 0.17 (1.98)D, 0.51 (1.88)D, -0.67 (1.0)D and 73.5 (105.0), respectively; while SER, spherical refraction, astigmatism, and astigmatism axis of infants in the control group were 0.13 (1.92)D, 0.25 (0.92)D, -0.94 (1.0)D and 90.0 (109.0). There were significantly differences in SER and spherical refraction between two groups (Z=-2.634, -2.353; P< 0.05). There were not statistically significant differences in astigmatism and astigmatism axis between two groups (Z=-0.144, -1.445; P> 0.05). At 18 months, SER, spherical refraction, astigmatism, and astigmatism axis of infants in the phototherapy group were 0.25 (1.25)D, 0.75 (1.50)D, -0.75 (0.7)D and 90.0 (125.0), respectively; while SER, spherical refraction, astigmatism, and astigmatism axis of infants in the control group were 0.13 (1.92)D, 0.33 (2.42)D, -0.58 (0.67)D and 98.0 (105.3), with non-significant difference between two groups (Z=-0.213, -0.988, -1.404, -0.697; P> 0.05). At 24 months, SER, spherical refraction, astigmatism, and astigmatism axis of infants in the phototherapy group were 0.17 (0.43)D, 0.50 (0.58)D, -0.50 (0.42)D and 92.5 (90.5), respectively; while SER, spherical refraction, astigmatism, and astigmatism axis of infants in the control group were 0.15 (1.33)D, 0.42 (1.47)D, -0.71 (0.63)D and 105.0 (64.0), with non-significant difference between two groups (Z=-0.285, -0.544, -1.322, -1.472; P> 0.05). After the age used as covariate and group as factor, a mixed effects model for the analysis of these factors and refractive development found that there were not statistical significance differences (t=1.365, 1.479, -0.668, -1.818; P>0.05); the analysis of the age and the level of astigmatism with statistically significant difference (t=7.609, P<0.05); the analysis of the age and SER, spherical refraction, astigmatism axis with non-significant difference (t=0.282, -1.659, 1.052; P>0.05).

During the neonatal period, infants gradually develop from hyperopia to emmetropia. The blue light exposure may not have a noticeable impact on refractive development in infants after short period.