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Jackson Cross Cylinder (JCC) Check Test for Uncorrected Astigmatism
SIDE TRIPS FROM THE ROUTINE DISTANCE SUBJECTIVE REFRACTION
Jackson Cross Cylinder (JCC) Check Test for Uncorrected Astigmatism
PURPOSE To test for the presence of a small amount of uncorrected astigmatism．
INDICATIONS
The JCC check test is indicated if the starting techniques of the refraction show no need for cylinder in the correction but the patient does not achieve sharp vision with a spherical correction．
SET-UP
·The phoropter contains the sphere from the end of the initial MPMVA．
STEP-BY-STEP PROCEDURE
1．Place -0.50 D of cylinder in the phoropter and remove -0.25 D from (add +0.25 to) the sphere in the phoropter．
2．Using the JCC lens，do a power check on the cylinder at axis 180，45，90, and 135．If the letters appear clearer to the patient with the minus-cylinder axis of the JCC aligned with the axis of cylinder in the phoropter，do not test the other axes．Leave the cylinder power in the phoropter and return to step 13 of the distance subjective refraction．
3．If the letters appear clearer to the patient when the plus-cylinder axis of the JCC is aligned with each of the four axes of cylinder in the phoropter，the patient probably has no significant uncorrected astigmatism．Continue with step 12 of the distance subjective refraction． |
