Prevalence of aniso-TA
Among 2300 eligible preschoolers, 1920 (participation rate 83.48%) children were examined. A total of404children wereuncooperative and no refraction measurements or biometric parameters from right or lefteyes were obtained after several attempts. Guardiansof 385 children did not complete the questionnaires, leaving 1131children(58.90%of eligible participants)included in this study.
There were no significant differences in characteristics of children (including age, gender, prevalence rate of aniso-TA) between children included in the analysis and those excluded from analysis due to missingdata in questionnaire.
The mean(±SD) age was 66.90 ±3.38months and 53.31% of participantswere boys.Han nationality children (1117, 98.76%)constituted the majority of the population.The prevalence of TA≥1.00 DC was 12.56% (95% CI=10.62% to 14.49%) in right eye and 12.73% (95% CI=10.79% to 14.68%) in left eye. Table 1 showsthe prevalence of aniso-TA stratified by sex and age. The prevalence of non-vectorial aniso-TA was 1.95%, whilethe prevalence of vectorial aniso-TAwas3.89%.Neither non-vectorial aniso-TAnorvectorial aniso-TAvariedwith sex or age (allP>0.05).Forty-four children had vectorial aniso-TA. Of them,twenty-sixchildren had aniso-J0t≥ 0.5,twenty-four children had aniso-J45t≥ 0.5,and six children hadboth.In addition, the prevalence of non-vectorial aniso-TA ≥2.00 DC was 0.18% and none had non-vectorial aniso-TA ≥3.00 DC.
Table 1. Prevalence of aniso- total astigmatism stratified by sex and age.
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Characteristics
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N (%)
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Vectorial aniso-TA * N (%, 95% CI)
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P
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Non-vectorial aniso-TA # N (%, 95% CI)
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P
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Sex
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0.77
|
0.74
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Boys
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603 (53.3%)
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22 (3.65%, 2.15 - 5.15)
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13 (2.16%, 0.99 - 3.32)
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Girls
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528 (46.7%)
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22 (4.17%, 2.46 - 5.88)
|
9 (1.70%, 0.60 - 2.81)
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Age (month)
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0.82
|
0.71
|
61 - 66
|
546 (48.3%)
|
20 (3.66%, 2.08 - 5.24)
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12 (2.20%, 0.95 - 3.43)
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67 - 72
|
685 (51.7%)
|
24 (3.50%, 2.12 - 4.88)
|
10 (1.71%, 0.66 - 2.76)
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Total
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1131 (100%)
|
44 (3.89%, 2.76 - 5.02)
|
|
22 (1.95%, 1.14 - 2.75)
|
|
* Vectorial aniso-TA was defined as a difference of ≥ 0.5 in J0 or J45between the two eyes. # Non-vectoral aniso-TA was defined as the difference of ≥ 1.0 diopter cylinder in absolute cylinder between the two eyes regardless of axis. N, number; CI, confidence interval.
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The components of vectorial aniso-astigmatism
There was a statistically significant association between aniso-J0t andaniso-J0c(ρ=0.15,P<0.001), and also between aniso-J45t and aniso-J45c(ρ=0.11, P<0.001). There was a statistically significant association betweenaniso-J0t and aniso-J0r(ρ=0.22, P<0.001), and also between aniso-J45t and aniso- J45r(ρ=0.11, P<0.001).
Comparison between groupstowards interocular biometric parameters
Table 2 shows comparisons of interocular differences in ocular biometric parameters between groups with vs. without aniso-astigmatism. Absolute value of interocular differencesin AL, mean CR, AL/CR, CCT, ACD, LT were calculated. The absolute value of interocular differences in AL, CR and AL/CR,ACD weresignificantly different between group A and group B(P=0.001, P<0.001, P=0.001, and P=0.01respectively). The absolute value of interocular differences in CR and AL/CRweresignificantlydifferent between group C and group D(both P<0.001),which were also significantly different between group Eand group F (both P<0.001).The absolute value of interocular differences in AL, CR and AL/CR were significantly different between group G and group H (P<0.001, P=0.001, and P<0.001 respectively).
Risk factorsforaniso-astigmatism
Comparisons for each risk factor between group A and group B were shown in sTable 1.Children in group A were more likely to haveabnormal 5 min-Apgar score (P<0.001) and parental astigmatism (P=0.03) than those in group B.In the multivariate analysis,two variables remained significantly associated with vectorial aniso-TA: 5min-Apgar score and parental astigmatism.Children with 5min-Apgar scorelower than 7were 6.42 times as likely to have vectorial aniso-TA as children with normal Apgar score (95%CI=2.63-15.69, P<0.001). Children with parental astigmatism were 2.03 times as likely to have vectorial aniso-TA as children without parental astigmatism (95%CI=1.09-3.79, P=0.03).
Comparisons for each risk factor between group C and group Dwere shown in sTable2.Children in group C were more likely to have older father at child birth (P=0.047), pre-term delivery (P=0.01), more outdoor activity (P=0.03) and being twin or triple(P=0.03) than those in group D.In the multivariate logistic regression analysis,two variables remained significantly associated with vectorial aniso-CA: being twin or triple and term delivery (Table 3).Children being twin or triple were 2.43 times as likely to have vectorial aniso-CAas those being monotocous(95%CI=1.05-5.60,P=0.04). Pre-termdelivery (OR=2.60, 95%CI=1.09-6.15, P=0.03) andpost-termdelivery (OR=3.61, 95%CI=1.31-9.96, P=0.01) weremore likely to have vectorial aniso-CA than full-term delivery.
Table 3. Independent Risk Factors for vectorial aniso-CA from Multivariate Logistic Regression
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Multivariate analysis
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Risk factors
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Adjusted OR
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95% CI
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P
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Twin or triple (Yes vs No)
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2.43
|
1.05-5.60
|
0.04
|
Term delivery
|
|
|
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Full-term
|
Reference
|
|
|
Pre-term
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2.60
|
1.09-6.15
|
0.03
|
Post-term
|
3.61
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1.31-9.96
|
0.01
|
OR, odds ratio; CI, confidence interval.
Comparisons for each risk factor between group E and group Fwere shown in sTable 3 and no statistically significant difference was found.Likewise, no statisticallysignificant variable was foundto be associated with vectorial aniso-RAin the multivariate logistic regression analysis.Comparisons for each risk factor between group G and group Hwere shown in sTable4.Children in group G were more likely to have younger paternal age at child birth, (P=0.049)abnormal 5 min-Apgar score (P=0.03) than those in group H. In the multivariate logistic regression analysis,only 5 min-Apgar score remained significantly associated with non-vectorial aniso-TA.Children with 5min-Apgar score lower than 7 were 4.99times as likely to have non-vectorial aniso-TA as children with normal Apgar score (95%CI=1.41-17.68, P=0.01).