The Epidemiology Of Astigmatism In 3～15 Years Old Children In A District Of Tianjin

Objective: To determine the prevalence and development of astigmatism, its epidemiological risk and its relationship with other ametropia in a 3~15 years old population in TianjinMethods: The data were sampled from the materials of population-based and cluster sampling of 9,248 eligible children in the project: The Epidemiologic Survey of Prevalence of Strabismus, Amblyopia and Refractive error of l~15-year Children in Tianjin (ESPSARC, Tianjin). 5998 children (3031 males and 2967 females) without severe media opacity that can bias the refractive measurement were random selected from the sample of ESPSARC as study subjective. A detailed self-designed questionnaire was administered to collect information of correlative disease and family medical history. Cycloplegic auto-refraction were performed and ETDRS chart was used to examine visual acuity. All examinations including assessment of outer eye, deviation, anterior and posterior segment, refractive error and visual acuity were performed by ophthalmologists, optometrists and doctorassistants after written consent from the parents having been obtained. Pilot study and interobserver agreement test was completed before the formal survey.Result: By the definition of ^0.50D, ^0.75D and ^l.OOD,the prevalence of astigmatism were 58.04%, 34.56% and 20.62% respectively. The astigmatic prevalence of age group 3~5, 6-11 and 12-15 were 38.05%, 30.35%, 39.41% respectively, and there is statistically significant difference between this three group ( x2==51.61, P<0.001). Hyperopic astigmatism was preponderant in children younger than 8 years old while myopic astigmatism was preponderant in children older than 9 years old. The constituent ratios of with the rule(WTR), against the rule(ATR) and oblique astigmatism(OA) were 50.18%, 16.23%, 33.59%. The proportion of with the rule astigmatism in slight, mild and server astigmatism were 63.24%, 77.68%, 93.48% respectively, and the proportion of anisometropia in slight, mild and server astigmatism were 2.94%, 3.58%, 9.02% respectively. The prevalence of slight, mild and server myopic astigmatism were 20.15%, 29.18%, 62.72% respectively while the prevalence of hyperopic astigmatism was 22.09%, 45.27%, 50.00% respectively.The difference of magnitude of astigmatism between anterior and posterior cycloplegia was not statistically significance by paired /-test (t=1.62, P=0.106), but the increase of Jo (t= 11.81, PO.001) and the decrease of J45 (t =2.75, P=0.006) were statistically significant.The probability of astigmatism symmetry between right and left eye was 47.08%, and the symmetry probability in WTR, ATR and OA were 55.58%, 29.94%, 17.18% respectively, in slight, mild and server astigmatism were 39.58%, 51.23%, 69.37% respectively.There was statistically significant difference of naked visualacuity(NVA) between slight astigmatism(0.82 ± 0.007) and normaleye(0.85±0.22), even after adjusted by the influence of axis of astigmatism and spherical refractive error(COANOVA, F=7.07, P<0.001). The difference of corrected visual acuity(CVA) betweenmild astigmatism (0.92+0.006) and normal eye (0.96±0.11) was alsosignificant even after adjusted by the influence of astigmatic axis and spherical refractive error (COANOVA, F =7.07, PO.001). 29.27% of server astigmatism (>1.5D) had CVA lower than 0.8. The mean CVA of simple myopic astigmatism, simple hyperopic astigmatism and mixed astigmatism was 0.925±0.007, 0.884±0.009, 0.905±0.005 respectively, which has significant difference among them by COANOVA (F=4.78, ZM).OO9). The mean CVA of WTR, ATR and OA was 0.910±0.004, 0.838±0.021, 0.892±0.014 respectively, which has significantdifference among them by COANOVA (F=6.978, P—0.007).Approximately, only 8.49% children with astigmatism had spectacle correction.After adjusted by other factors, only hyperopia more than 3.0D (OR= 4.54, 95%CI: 2.80-7.36), myopia less than -3.0D (OR= 2.46,95%CI: 2.12-2.85), father history of hyperopia (OR= 3.05, 95%CI: 1.33-7.04), delivery history of uterine-incision (OR=1.24, 95%CI: 1.11-1.39) and prematurity history (OR= 1.35, 95%CI: 1.07-1.71) were associated with the prevalence of astigmatism with statistic significance using Logistic regression. Conclusion:1. By the definition of ^0.50D, ^0.75D and ^l.OOD, theprevalence of astigmatism of 3-15 years old children was 58.04%, 34.56% and 20.62% respectively, which was higher than that of Beijing rural and lower than that of Guangzhou urban.2. With a relatively high level in 3-5 years old the prevalence of astigmatism declined after 6 years old, and maintained in low during 8-11 years old, then upgraded from 12 years old.3. The prevalence of astigmatism increased with the severity of myopia or hyperopia.4. The proportion of hyperopic astigmatism and mixed astigmatismdescended with the age, but that of myopic astigmatism ascended with the age. Hyperopic astigmatism was preponderant in children younger than 8 years old while myopic astigmatism was preponderant in children older than 9 years old. Mixed astigmatism was the least all the time.5. In our sample, WTR was the most common astigmatism while OA was the second and ATR the least.6. With the severity of astigmatism, the proportion of WTR became higher while ATR and OA became lower.7. The prevalence of anisometropia also increased with the severity of astigmatism.8. The probability of astigmatism symmetry between right and lefteye was merely 47.08%. The probability of astigmatism symmetry increased with the severity of astigmatism, and decreased ordinally from WTR to ATR and OA.9. The difference of magnitude of astigmatism between anterior and posterior cycloplegia was not significance, while the orthogonal astigmatism became more WTR and oblique astigmatism became morewith the negative axis at 45 ° after cycloplegia.10. Astigmatism equal or more than 0.5D can cause NVA todecrease, and astigmatism equal or more than 1.0D can cause CVA to decrease. The influence of astigmatism on VA increased with the severity of astigmatism. 29.27% of server astigmatism (>1.5D) had CVA lower than 0.8. Hyperopic astigmatism had greater influence on VA than myopic and mixed astigmatism. Against the rule astigmatism had greater influence on VA than with the rule and oblique astigmatism.11. Hyperopia more than 3.0D, myopia less than -3.0D, fatherhistory of hyperopia, delivery history of uterine-incision and prematurity history may be associated with the prevalence of astigmatism.