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Molecular Anatomy of the Vertebrate Eye
Published in Marcel E. Nimni, Collagen, 1988
The wall of the eye consists of three layers. The outermost layer is composed of opaque sclera and transparent cornea which provide a slightly elastic envelope that maintains the shape of the eye. The middle vascular layer is made up of the choroid, ciliary body, and iris. The innermost layer is the light-sensitive retina (Figure 1). The cornea is composed primarily of extracellular matrices and is covered on its anterior and posterior surfaces by a sheet of cells. The multilayered epithelium and a single-layered endothelium are apposed to their associated basement membranes. The anterior chamber is bounded by the cornea anteriorly and the iris posteriorly. The lens lies behind the iris and within the anterior and posterior capsule, and is attached to the muscle of the ciliary body by the fine fibers of the zonules of Zinn. The vitreous is the transparent gelatinous mass that fills the eye behind the lens. The retina is formed of light-sensitive nerve cells that transmit the visual impulses to the brain via the optic nerve.
Ocular manifestations in classic homocystinuria
Published in Ophthalmic Genetics, 2021
Patrícia Ioschpe Gus, Karina Carvalho Donis, Diane Marinho, Tiago Franco Martins, Carolina Fischinger Moura de Souza, Rafael Barboza Carloto, Gabriel Leivas, Ida Vanessa Doederlein Schwartz
It is well known that early diagnosis can prevent the ocular manifestations of HCU, but the absence of newborn screening for this condition in Brazil means that all patients were diagnosed late. Weak zonules of Zinn and sclera can lead to lens instability, increased refractive index, iridodonesis and globe enlargement, all of which contribute to progressive myopia at a young age. Increasing myopia is useful as a sign of treatment refractoriness or poor adherence, with poor biochemical control, and the presence of high myopia in HCU patients is around 45% (9–12).