True anophthalmia is defined as a total absence of tissues of the eye; it is classified into 3 types. Primary anophthalmia, which is rare and usually bilateral, occurs when the primary optic vesicle fails to grow out from the cerebral vesicle at the 2-mm stage of embryonic development. Secondary anophthalmia is rare and lethal and results from a gross abnormality in the anterior neural tube. Consecutive anophthalmia presumably results from a secondary degeneration of the optic vesicle.
Figure 3-1 Right microphthalmic orbit. Three-dimensional computed tomography (CT) reconstruction shows a hypoplastic right orbit with microphthalmia.
(Courtesy of Bobby S. Korn, MD, PhD.)
Because orbital development is partially dependent on the size and growth of the globe, the bones of the orbit, the eyelids, and also the adnexal structures fail to develop and remain hypoplastic in anophthalmia. Intervention requires measures that address all of these issues, not just the missing eye.
Excerpted from BCSC 2020-2021 series: Section 10 - Glaucoma. For more information and to purchase the entire series, please visit https://www.aao.org/bcsc.