Measurement of Angle Deviation Using Digital Photographs

ABSTRACT

PURPOSE: The prism-cover test has been known to be the most accurate method in measuring ocular angle deviation, but the Hirschberg test is used in poorly cooperative patients. To enhance the accuracy of Hirschberg test, we designed a geometric model using digital photographs. METHODS: Fifty normal volunteers were included in this study, who had no ocular disorders. Digital photographs were obtained in the subjects seated 2 m in front of the fixation targets and the camera was set 1 m in front of subjects. In each photograph, the apparent width of the cornea and the distance from the corneal light reflex to the limbus were measured using computer program for calculation of angle deviation. Then we compared the calculated angle deviation with the actual one. RESULTS: Calculated angle deviations with digital image photographs were corresponded to the actual ones from esodeviation 40delta to 10delta (p>0.05), whereas in esodeviation 60delta, 70delta and exodeviation, the larger the deviation angle, the larger the calculated angle composed with the actual one. CONCLUSIONS: Angle deviation measurement using digital photographs appears to be relatively precise and its clinical application will be available in measuring angle deviation of esodeviation.