The accuracy of experienced strabismologists using the Hirschberg and Krimsky tests.

OBJECTIVE: The purpose of the study was to assess the accuracy of a group of strabismologists applying the Hirschberg and Krimsky tests.
DESIGN: A clinical trial. PARTICIPANTS: Sixteen very experienced strabismologists participated in this study. INTERVENTION: The participants were asked to evaluate slides of four different patients using the Hirschberg method and to evaluate two of the four patients with the Krimsky method. The slides included a patient with 25 delta left esotropia, a patient with 25 delta right exotropia, a patient with 80 delta esotropia with a positive angle kappa, and a patient with 75 delta infantile esotropia. Alternate prism and cover testing was performed immediately after the photograph was taken and considered to be the actual deviation of the patient. MAIN OUTCOME MEASURE: Measured was the accuracy in assessing the angle of strabismus.
RESULTS: With the Hirschberg method, each participant underestimated at least one patient by at least 10 delta. In addition, the participants tended to underestimate both large and small angle esotropic and exotropic patients with greater errors of estimation occurring with larger angles of strabismus. With the Krimsky method, a majority of participants overestimated at least one patient by 10 delta and showed difficulty in appreciating differences of 5 delta. In addition, the authors noted inconsistent responses by each participant.
CONCLUSION: The Hirschberg and Krimsky methods are substantially less accurate than the alternate prism and cover test.