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ABO # STWQO100-2
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Astigmatism can be detected by using a couple of subjective techniques. The first we will talk about is the “clock dial.” This technique uses a plus lens to “fog” the patient to approximately 20/40, typically 3 clicks of plus power above best acuity with the “rough” sphere. A dial that looks like the hands on a clock is placed at 20 feet, and the patient is to report if one set of hands on the clock looks clearer. If all the hands on the clock are equal, no astigmatism exists; if one set of hands is clearer or sharper, then there is astigmatism present. The axis can be determined by multiplying the lower numbered hand on the clock by thirty. For example, if the patient reports the 2 and 8 o’clock positions to be clearest, then the axis would be 60 degrees. |
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