2020–2021 BCSC Basic and Clinical Science Course™
11 Lens and Cataract
Chapter 4: Embryology and Developmental Defects
Normal Development of the Lens
The formation of the human crystalline lens begins very early in embryogenesis (Fig 4-1; Video 4-1). At approximately 25 days of gestation, 2 lateral evaginations, called the optic vesicles, form from the forebrain, or diencephalon. As the optic vesicles enlarge and extend laterally, they become closely apposed and adherent to the surface ectoderm, a single layer of cuboidal cells, in 2 patches on either side of the head. (See BCSC Section 2, Fundamentals and Principles of Ophthalmology, for additional discussion and illustrations of ocular development.)
Lens development. Go to www.aao.org/bcscvideo_section11
to access all videos in Section 11.
At approximately 27 days of gestation, the ectoderm cells that overlie the optic vesicles become columnar. This area of thickened cells is called the lens placode. Growth factors of the bone morphogenetic protein (BMP) family are required for formation of the lens placode and, subsequently, the lens.
Figure 4-1 Embryologic development of the lens.
(Illustration by Christine Gralapp.)
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.