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).
Congenital Aphakia
The lens is absent in congenital aphakia, a very rare anomaly. Congenital aphakia can be classified into 2 types:
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In primary aphakia, the lens placode fails to form from the surface ectoderm in the developing embryo.
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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.