| Objective: To investigate the distribution of visual acuities of children of 3-15-year old through detection with ETDRS eye chart, and to obtain the corresponding information to be statistically analyzed. Also to discuss the relationship between visual acuities and refraction states and correlation factors of visual acuities.Methods: The data of subjects were sampled from the materials of population-based and cluster sampling of 10,000 eligible children in the project- The Epidemiologic Survey of Prevalence of Strabismus, Amblyopia and Refractive error of 1-15-year Children in Tianjin (ESPSARC, Tianjin). The children who refused to be examined and are unwilling to cooperate with the examiners were excluded. The subjects included 1630 children of age group 3~15 years old (825 boys and 805 girls) and were sampled by the method of random digits table.Before the formal examinations, survey workers were trained with knowledge of the significance, purpose, methods and detailedsteps of the survey. They were familiarized with proper instructions of completing different types of tables and lists, the meanings and contents of various variables in the unified survey tables, the inspectoscopes and examination flow. Referring to some literatures, we established the corresponding definitions and standards and conducted the pilot study.The examiners enumerated all sampled children and recorded the results. The self-designed Table for Survey of Strabismus, Amblyopia and Refractive error of Children was used in the questionnaire investigation and examination of the subjects. The collected data include: general material (name, sex, age, nationality, address, school, grade, class, names of parents or guardians), the history of eye-related diseases of parents, mother's age and pregnancy history, birth conditions of the child (birth weight, delivery mode), child's past history of eye diseases, ophthalmological examinations (the examinations of distant visual acuity include uncorrected, presenting and corrected visual acuity, cover-uncover test, ocular movement, stereoscopic visual acuity, retinal correspondence, blepharon, conjunctiva, corneas, pupils, lens, the refraction before and after cycloplegia, vitreous and retina, etc.).The fieldworkers are composed of ophthalmologists, doctorassistants and optometrist. The ophthalmologists took charge of the fieldwork supervisors to guarantee the survey quality. The data was examined, verified and recorded by special persons. The data input was done twice to ensure accuracy. The data collection were standardized and quantified firstly. The frequency statistics were used to describe the distribution of visual acuities of 3~15-years old children. T-test and ANOVA were used to compare the differences of visual acuity average between boys and girls, between two eyes and among different ages. The distributions of normal visual acuity and subnormal visual acuity were described. Chi-square test was used to compare the significance of differences among the distributions of visual acuities of different ages, sexes and birth conditions. The distribution of refraction states under different visual acuity and the visual acuity average under different refraction state were described. Correlation analysis of the relationship between visual acuity and refraction state was done.Results:1. The visual acuity average of 3-15-year old children is 0.67, in which males are 0.69 and females are 0.64, indicating significant difference (t =5.009,p=0.000). There is no significant difference between right and left eye(t=0.421,p=0.673).2.The prevalence of the normal visual acuity of 3-15-year old children is 43.68% according to the population number, in which males are 393 (55.2%) and females are 319 (44.8%); 50.09% according to eye numbers, in which males are 884 (54.13%), females are 749 (45.87%). The comparison among different ages showed that the prevalence in the primary school group is higher than the pre-school group and the junior-high-school group, the difference is significant. The prevalence in boys is higher than in girls, the difference is significant. The prevalence in subjects whose parents have a history of eye diseases is lower than those whose parents have no history of eye diseases, and the difference is significant. The prevalence in subjects with premature birth history is lower than those without a history of prematurity, with the p value approaching 0.05.3.Uncorrected visual acuity 0.5 or worse in the better eye was found in 490( 30.07%) children, including 26( 1.6%) with visual acuity 0.1 or worse in the better eye. Of those with uncorrected visual acuity 0.5 or worse in the better eye, 246(50.2%) wore glasses. Presenting visual acuity 0.5 or worse in better eye was found in 300 (18.40%) children, including 2 with the visual acuity 0.1 or worse in the better eye. With corrected visual acuity, the number decreased to 27(1.66%); no person had a corrected visual acuity 0.1 or worse inbetter eye.4. The proportion of subnormal visual acuity in uncorrected visual acuity is 56.32%, in presenting visual acuity 51.60%, and in corrected visual acuity 11.90%.5. There is significant difference among the distribution of uncorrected visual acuity, presenting visual acuity and corrected visual acuity in 3-15-year old children. There is no significant difference between uncorrected visual acuity and presenting visual acuity in 3~ll-year old group; there is significant difference between uncorrected visual acuity and presenting visual acuity in 12~15-year old group. There is no significant difference between presenting visual acuity and corrected visual acuity in 3~8-year old children with glasses, but there is a significant difference in children of 9 years and older. The uncorrected visual acuity average of children without glasses is 0.75, and the corrected visual acuity is 0.90; there is significant difference between uncorrected visual acuity and corrected visual acuity of different age groups.6. The corrected visual acuity is normal in 79.52% of 3-15-year old children with subnormal visual acuity: subnormal in 19.28%, low-visual acuity in 0.65%, blind in one eye in 0.44%.7. In children with normal visual acuity, about 16% of eyes withnormal visual acuity are mildly myopic. In children with subnormal visual acuity, 38.6% eyes are emmetropic, and 36.1% eyes are mildly myopic.8. The uncorrected visual acuity is negatively correlated with the refraction (r=-0.690,p=0.000). The refraction of myopia is more correlated with the uncorrected visual acuity (r= -0.744, p=0.000)than with the refraction of hyperopia (r= -0.383, p=0.000) . The refraction of piano (0.00D) was found in 121(3.71%) eyes. In refraction of myopia, normal eyes are 26.15%, and the strongest myopia can be corrected to obtain normal visual acuity. In refraction of hyperopia , normal eyes are 65.86%. The refraction of moderate and strong hyperopia cannot be corrected to normal.Conclusion:1 .The distribution of uncorrected visual acuity:As the age increases, the uncorrected visual acuity and the prevalence increases gradually at first and then decreases at 3~7 years, plateauing at 8-12 years, and then decreasing sharply after 13 years.2. The distribution of uncorrected, presenting and corrected visual acuity:There is significant difference among the distribution of uncorrected visual acuity, presenting visual acuity and corrected visual... |
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