. Refraction and how to refract : including sections on optics, retinoscopy, the fitting of spectacles and eye-glasses, 80° 0. Fig. 102.—Illustrating Astigmatismwith the rule. Fig. 103.—Illustrating Astigmatismagainst the Rule. degrees (inclusive) either side of 90 degrees (see ); or a minus cylinder at axis 180 degrees, or within45 degrees (inclusi\e) either side of 180 degrees. Forexample, if an eye requires a plus cylinder at 45 degrees,or at any axis from 45 degrees up to 135 degrees (inclu-sive), taking axis 90 as the median line, then the astig-matism is ivitJi the rule. But
. Refraction and how to refract : including sections on optics, retinoscopy, the fitting of spectacles and eye-glasses, 80° 0. Fig. 102.—Illustrating Astigmatismwith the rule. Fig. 103.—Illustrating Astigmatismagainst the Rule. degrees (inclusive) either side of 90 degrees (see ); or a minus cylinder at axis 180 degrees, or within45 degrees (inclusi\e) either side of 180 degrees. Forexample, if an eye requires a plus cylinder at 45 degrees,or at any axis from 45 degrees up to 135 degrees (inclu-sive), taking axis 90 as the median line, then the astig-matism is ivitJi the rule. But if an eye should require aplus cylinder within 45 degrees either side of 180 degrees,then the condition is one of astigmatis))i against the rule.(See Hg. 103.) A plus or minus cylinder at 45 degrees 130 REFRACTION AND HOW TO REFRACT. or 135 degrees is recognized as asiigmatisDi xvitJi therule. 7. Homonymous astigmatism is the condition in whichthe cyHndcr axis in each eye is the same. 8. Heteronymous astigmatism is the condition in whichthe astigmatism in one eye is with the rule, and in the othereye against the rule. For
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