Orbital development involves key contributions from ectodermal, mesodermal, and neural crest–derived elements. By the fourth week of gestation, the frontonasal and maxillary processes of neural crest cells occupy the space that surrounds the optic cups. The bones, cartilage, fat, and connective tissues of the orbit develop from these cells. All bones of the orbit are membranous except the sphenoid, which is initially cartilaginous. Ossification begins during the third month of gestation, and fusion occurs between the sixth and seventh months.
Excerpted from BCSC 2020-2021 series: Section 2 - Fundamentals and Principles of Ophthalmology. For more information and to purchase the entire series, please visit https://www.aao.org/bcsc.