Axial lengths of 30 eyes (15 subjects), measured by ultrasonography, ranged from 20.6-26.3 mm. Using a fixed light source, each eye was photographed as monocular fixation was changed over an 8-deg range in 2-deg steps. Hirschberg ratios obtained from the photographs show a low correlation with axial length (0.07), and the mean value, 24 prism diopters per millimeter (S.D. = 7), further supports recent recommendations that the traditional ratio of 12 or 14/1 be replaced by a more correct ratio of 22/1.
Based in part on a thesis submitted in partial fulfillment of the requirement for the Doctor of Optometry degree. Presented before the Annual Meeting of the American Academy of Optometry, Birmingham, Alabama, December 13, 1977. Received December 20, 1977; revised April 26, 1978.
† Optometrist, Ph.D., Member of Faculty, F.A.A.O.
College of Optometry
Forest Grove, Oregon 97116
© 1978 American Academy of Optometry