Evaluates the correlation between axial length and Hirschberg ratios, suggesting improved measurement accuracy.
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.
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Carter et al. (1978) studied this question.
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