The studies were carried out on the difference of degrees and axis between total astigmatism (TA) and corneal astigmatism (CA) in 7353 eyes, from 3 to 73 years old, and revealed as follows,
1) In 75.5% of all subjects, the difference was less than 1 dptr., and 40% of the 3750 eyes had no difference in the axis within 10 degrees, between total and corneal astigmatism.
2) In both total and corneal astigmatism, the astigmatism with the rule was the largest in number: Total astigmatism 61.9%, Corneal astigmatism 66.9%.
3) In 57% of the 7353 eyes, the CA was larger than TA and in 5% the TA was larger. This ratio was as same as in the different spherical refractive status.
4) Eyes with larger CA than TA appeared to have astigmatism with the rule, the others and those TA was larger than CA appeared to have against the rule; however myopic eyes in the latter group seemed to have a direct astigmatism.
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