2020–2021 BCSC Basic and Clinical Science Course™
8 External Disease and Cornea
Chapter 8: Systemic Disorders With Corneal and Other Anterior Segment Manifestations
Skeletal and Connective Tissue Disorders
Osteogenesis imperfecta is a rare, dominantly inherited condition occurring in 1 in 20,000 live births. There are 4 types resulting from mutations in the COL1A1 and COL1A2 genes. The disease results in defects in the skeleton and teeth, hearing deficits, and ocular anomalies.
The genetic mutation causes abnormalities of the α1 or α2 chain of type I collagen. As a result, the collagen fibrils fail to mature to their normal diameters.
Patients with osteogenesis imperfecta are susceptible to brittle bones and multiple skeletal fractures. Hearing loss is common; the prevalence ranges from 50% to 92% in some studies. Hearing loss may be conductive, mixed, or sensorineural and is more common after adolescence. Patients are also predisposed to brittle teeth. Ocular manifestations include blue sclera (Fig 8-11) and reduced central corneal thickness (average of 450 μm). The blue sclera is present throughout life in type I osteogenesis imperfecta, but fades within the first few years of life in the other 3 types. Other rare ocular findings include optic nerve damage due to fractures in the calvarial bones, keratoconus, and megalocornea. Table 8-6 summarizes other conditions associated with blue sclera.
Treatment with oral bisphosphonates reduces bone resorption, and aggressive orthopedic management of fractures is indicated. Low-impact exercise might help preserve bone and muscle integrity.
Figure 8-11 Clinical photograph showing blue sclera in a patient with osteogenesis imperfecta.
(Courtesy of Stephen E. Orlin, MD.)
Table 8-6 Conditions and Medications Associated With Blue Sclera
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.