Nearly all books on refraction give a very large and probably undue amount of space to the astigmatic fan test. There have been a considerable number of later writers who affirm that the astigmatic fan test combined with the fogging method even obviates the necessity for the use of cycloplegics. It is my purpose to prove that the test is very unreliable in a large percentage of cases, and that only by accident is it ever accurate.
It is possible to have the lines appear unlike when the patietn has no regular astigmatism. Moreover, it is often true that the lines may look alike in the principal meridians, and yet the patient and victim may still have remaining some astigmatism that ought to have been corrected. Considerable fault may be found with the test, for the additional reason that the average patient, from inexperience and lack of
STEVENSON DW. THE UNRELIABILITY OF THE ASTIGMATIC FAN OR CLOCK DIAL TEST. JAMA. 1909;LIII(1):8–12. doi:10.1001/jama.1909.92550010014002
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