As the lens pit continues to invaginate, the stalk of cells connecting it to the surface ectoderm degenerates by programmed cell death (apoptosis), separating the lens cells from the surface ectoderm. The resultant sphere, a single layer of cuboidal cells encased in a basement membrane (the lens capsule), is called the lens vesicle. At the time of its formation at 30 days of gestation, the lens vesicle is approximately 0.2 mm in diameter.
Because the lens vesicle was formed through a process of invagination of the surface ectoderm, the apices of the cuboidal cells are oriented toward the lumen of the lens vesicle, with the base of each cell attached to the capsule around the periphery of the vesicle. While the lens vesicle is forming, the optic vesicle is simultaneously invaginating to form the 2-layered optic cup.
Excerpted from BCSC 2020-2021 series: Section 11 - Lens and Cataract. For more information and to purchase the entire series, please visit https://www.aao.org/bcsc.