Biometric study of the optic canal during cranial development.

To study optic canal dimensions and symmetry during cranial development, 146 silicon rubber left- and right-side models of the optic canal were cast from 51 dry skulls and 22 individual bones. The sample was divided in three age groups: fetuses (including newborns), children and adults with ages ranging from seven months of fetal life to 68-year-old. A digital caliper was used to measure the optic canal orbital and cranial diameters as well as model length. Results for the right and the left sides were, respectively, in millimeters: a) Maximum diameter of the orbital opening: fetuses, 4.68/4.47--children, 5.51/5.41--adults, 5.43/5.34; b) Minimum diameter of the orbital opening: fetuses, 2.89/2.84--children, 3.54/3.61--adults, 3.78/3.73; c) Diameter of the cranial opening: fetuses, 3.79/3.76--children, 4.67/4.72--adults, 5.24/5.43; d) Length of the optic canal: fetuses, 3.27/3.05--children, 3.93/3.71--adults 4.94/5.21. The diameter of the cranial opening of the optic canal increases significantly (p < 0.001) during the fetal period and throughout child and adulthood. The greater and smaller orbital apertures increase during the fetal period and during childhood, keeping the same size in adulthood. Optic canal length increases at some point between childhood and adulthood. Concerning symmetry, the only significant difference found was greater right than left optic canal diameter on the orbital side.