2020–2021 BCSC Basic and Clinical Science Course™
2 Fundamentals and Principles of Ophthalmology
Part IV: Biochemistry and Metabolism
Chapter 11: Vitreous
Biochemical Changes With Aging and Disease
Genetic Disease Involving the Vitreous
Stickler syndrome is most commonly due to a mutation in the gene COL2A1, which codes for type II collagen, a major component of vitreous collagen fibers. Affected patients have an optically empty vitreous due to premature liquefaction with peripheral condensation, which may induce retinal detachment (see also BCSC Section 12, Retina and Vitreous). Mutations in both the α1(II) and α1(XI) collagen chains have been shown to be responsible for this syndrome.
Wagner syndrome is another condition in which patients present with an optically empty vitreous and have an increased risk of retinal detachment. As mentioned earlier in this chapter, these patients have mutations in the VCAN gene, encoding versican, which participates in formation of the vitreous gel.
Figure 11-6 The role of ascorbate in the vitreous cavity. A, The vitreous acts as a barrier to the diffusion of oxygen within the posterior segment. The available ascorbate binds with oxygen, forming dehydroascorbate, which is taken up by surrounding cells. B, In postvitrectomized eyes, the amount of oxygen exceeds the capacity for clearance, leading to the production of reactive compounds that create oxidative stress in the lens, which in turn accelerates cataract formation.
(Illustration by Cyndie C.H. Wooley.)
Robin NH, Moran RT, Ala-Kokko L. Stickler Syndrome. GeneReviews [Internet]. Seattle, WA: University of Washington, Seattle; 1993–2019.
Excerpted from BCSC 2020-2021 series: Section 2 - Fundamentals and Principles of Ophthalmology. For more information and to purchase the entire series, please visit https://www.aao.org/bcsc.