A lens coloboma involves flattening or notching of the lens periphery (Fig 23-6). It may be associated with a coloboma of the iris, optic nerve, or retina, all of which are caused by abnormal closure of the embryonic fissure. The term lens coloboma is a misnomer because the lens defect is caused by absence or stretching of the zonular fibers in the affected area (usually inferonasally) and is not directly due to abnormal embryonic fissure closure. In more significant colobomatous defects, lens dislocations may occur superiorly and temporally. Most colobomatous lenses do not progressively worsen.
Figure 23-6 Lens coloboma, viewed with slit-beam illumination (A) and retroillumination (B). The lens is subluxated inferonasally, and there is a notch in the superotemporal portion of the lens where zonules are lacking.
(Courtesy of Gregg T. Lueder, MD.)
Excerpted from BCSC 2020-2021 series: Section 10 - Glaucoma. For more information and to purchase the entire series, please visit https://www.aao.org/bcsc.