Development of the cornea during fetal life: comparison of corneal and bulbar diameter

Two hundred twenty undamaged human fetuses without external malformations were supplied by the human embryo and fetus collection at the Department of Anatomy, Kyoto University. The diameters of the cornea and eyeball were measured by slide calipers under a stereomicroscope. The various diameters of the eyeball showed a parallel, linear increase from the 12th to the 28th week of menstrual age. Corneal diameters appeared to increase in parallel with the eyeball as a whole until the 16th week of menstrual age; later on their rate of growth declined. The corneal limbus could be recognized macroscopically at the 17th week of menstrual age and was distinctly seen from the 20th week of menstrual age. The corneal curve at the limbus began to be a little convex at the 21st week of menstrual age and became distinctly convex from the 23rd week. The cornea was transparent from the 12th to the 28th week of menstrual age. The sclera lost its transparency from the 21st week. It is significant that during fetal life the sagittal diameter of the eyeball is shorter than the vertical and transverse diameters.