2020–2021 BCSC Basic and Clinical Science Course™
11 Lens and Cataract
Chapter 4: Embryology and Developmental Defects
Normal Development of the Lens
Lens Sutures and the Fetal Nucleus
As lens fibers grow anteriorly and posteriorly, a pattern emerges where the ends of the fibers meet and interdigitate with the ends of fibers arising on the opposite side of the lens, near the anterior and posterior poles. These patterns of cell association are known as sutures. Y-shaped sutures are recognizable at approximately 8 weeks of gestation; an erect Y-suture appears anteriorly and an inverted Y-suture appears posteriorly (Fig 4-2). As the lens fibers continue to form and the lens continues to grow, the pattern of lens sutures becomes increasingly complex, resulting in 12 or more suture branches in the adult eye. The mechanisms responsible for the precise formation and changing organization of the suture pattern remain obscure.
The human lens weighs approximately 90 mg at birth, and it increases in mass by approximately 2 mg per year throughout life as new fibers form. With increasing age, the central, or oldest, lens fibers gradually become less malleable, and the lens nucleus becomes more rigid. This process progressively reduces the amplitude of accommodation.
Figure 4-2 Y-shaped sutures, formed during embryogenesis, are visible within the adult lens with the use of the slit lamp.
(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.