2020–2021 BCSC Basic and Clinical Science Course™
11 Lens and Cataract
Chapter 4: Embryology and Developmental Defects
Congenital Anomalies and Abnormalities
Most significant congenital anomalies of the eye and orbit are apparent on ultrasonography before birth. As a rule, the more profound the abnormality, the earlier in development it occurred. Disorders of the lens include abnormalities in lens shape, size, location, and development, as well as cataract (Table 4-1).
The lens is absent in congenital aphakia, a very rare anomaly. Congenital aphakia can be classified into 2 types:
In primary aphakia, the lens placode fails to form from the surface ectoderm in the developing embryo.
In secondary aphakia, the more common type, the developing lens is spontaneously absorbed.
Both forms of aphakia are usually associated with other malformations of the eye.
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.