Objective: This study aimed to analyze the trends and characteristics of early visual development in infants and young children. Methods: A prospective cohort study was conducted, including full-term infants born between 2008 and 2013 at the Maternal and Child Health Hospital in Sanhe City, Hebei Province, China. Visual acuity was assessed at three time points 42 days after birth, 9 months of age, and 18 months of age, using the Teller Acuity Card Ⅱ (TAC Ⅱ) grating visual acuity test. At 3 years of age, visual acuity was assessed using the Lea Symbols chart and converted to grating visual acuity. Visual acuity of both eyes was measured at 42 days, 9 months, and 18 months. For children at 9 and 18 months, monocular visual acuity was also assessed, while at 3 years of age, monocular visual acuity was measured. Visual acuity measurements at different time points and changes in visual acuity within each period were recorded. The visual development of the participants was analyzed and compared with previous literature results. Results: A total of 1 496 children were included in the study, including 773 males (51.67%) and 723 females (48.33%). The binocular visual acuity at 42 days, 9 months, and 18 months was 0.9 (0.6, 1.1), 6.4 (6.4, 9.6), and 9.6 (9.6, 9.6) cycles per degree (cpd), respectively, with statistically significant differences (P<0.001). Visual acuity increased by a factor of 3.21±0.70 between 42 days and 9 months, and by a factor of 0.23±0.48 between 9 and 18 months. At 9 months of age, the monocular visual acuity in the right and left eyes was 6.4 (4.8, 6.4) cpd, which remained the same at 18 months, and the median visual acuity at 3 years of age for both eyes was 18.75 cpd, with a Snellen visual acuity of 20/32 (20/40, 20/32). The differences in binocular visual acuity at each time point were not statistically significant (all P>0.05). At 9 months of age, 68.7%(633/921) of children had visual acuity of ≥6.5 cpd, which increased to 92.7%(342/369) at 18 months. Monocular visual acuity increased by a factor of 0.26±0.46 between 9 and 18 months, and by a factor of 1.36±0.52 between 18 months and 3 years. At 9 months of age, 72.01% (921 out of 1 279) of children who completed binocular visual acuity testing also underwent monocular visual acuity testing, while this proportion decreased to 35.83% (369 out of 1 030) at 18 months. Visual acuity improved with increasing age (P<0.001). The visual acuity of children at each age group in this study was higher than that reported in the literature for children in Guangzhou (P<0.001). Conclusions: The visual acuity of healthy infants and young children below 3 years of age improves with age. Visual development progresses rapidly before 9 months of age, slows down afterward, and then resumes rapid growth at 18 months of age.
目的： 分析婴幼儿早期视力成长发育的趋势和特点。 方法： 前瞻性队列研究。连续纳入2008年至2013年于河北省三河市妇幼保健院出生的足月儿，在生后42 d、9月龄、18月龄3个时间点使用Teller Acuity Card Ⅱ（TACⅡ）条栅视力卡进行选择性观看视力检查，得到其条栅视力；3岁时采用Lea Symbols图形视力表进行视力检查并将结果转换为条栅视力。受试儿童在42 d、9月龄、18月龄3个时间点均检查双眼视力，对9和18月龄儿童增加单眼视力检查，3岁儿童检查单眼视力。记录不同时间点各项视力及各时间段内视力变化值，分析受试儿童的视力发育情况，并与以往文献结果进行比较。 结果： 共纳入1 496名儿童，其中男性773名（51.67%），女性723名（48.33%）。受试儿童在42 d、9月龄和18月龄时双眼视力分别为0.9（0.6，1.1）、6.4（6.4，9.6）和9.6（9.6，9.6）周/度（cpd），差异有统计学意义（P<0.001）。视力在42 d至9月龄期间增长了（3.21±0.70）倍，在9至18月龄期间增长了（0.23±0.48）倍。受试儿童在9月龄时右眼和左眼的单眼视力均为6.4（4.8，6.4）cpd；18月龄时均为6.4（6.4，9.6）cpd；3岁时右眼和左眼视力中位数均为18.75 cpd，Snellen视力均为20/32（20/40，20/32），各时间点双眼间视力的差异无统计学意义（均P>0.05）。9月龄时视力≥6.5 cpd者占68.7%（633/921），18月龄时则为92.7%（342/369）。9至18月龄期间单眼视力增长了（0.26±0.46）倍，18月龄至3岁期间则增长了（1.36±0.52）倍。9月龄时，1 279名完成了双眼视力检查的儿童中有72.01%（921名）完成了单眼视力检查，18月龄这一比例降至35.83%（369/1 030）。儿童视力随年龄提高（P<0.001）。本研究各年龄儿童的视力均高于文献中广州儿童的视力（P<0.001）。 结论： 3岁以内的健康婴幼儿的视力水平随年龄提高，9月龄之前视力发育迅速，之后变得平缓，至18月龄又开始持续快速增长。.