Axial length and the Hirschberg test.
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.
D000328:Adult; D005123:Eye / Q000033:anatomy & histology*; D006801:Humans; D012015:Reference Standards; D013285:Strabismus / Q000175:diagnosis*; D014787:Vision Tests / Q000592:standards*