Extraocular muscle surgery in early infancy--anatomical factors.

The dimensions and topographical anatomy of 26 eyes from 14 neonates and infants were measured and photographed with special attention to the insertional position of the extraocular muscles. Additional measurements were made in histologic preparations of 12 normal infant eyes. Although the diameters of the neonatal eyes were found to be about 70% of the adult eyes, the volumes of the globes were only about half, and the surface areas even less. The insertions of the rectus muscles were about 2 mm nearer to the cornea than in emmetropic adult eyes, but some were close to or at the equator. The posterior segments of the neonatal eyes were much less developed than the anterior, so that the oblique insertions, as compared to the adult eye, were closer to each other, to the horizontal meridian and to the posterior pole. In some neonatal specimens the inferior oblique insertion was so close to the optic nerve that tenotomy at that point would have jeopardized some of the posterior ciliary vessels and nerves. The dramatic postnatal growth of the eye occurs in the scleral segment; there is minimal corneal growth. About half of the total lifetime increase in the diameters, volume and total surface area of the human eye occurs in the first six months of life. In the six-month-old specimens the volume of the globe and the surface area of the sclera had almost doubled as compared to the neonatal eyes.(ABSTRACT TRUNCATED AT 250 WORDS)