2020–2021 BCSC Basic and Clinical Science Course™
4 Ophthalmic Pathology and Intraocular Tumors
Part I: Ophthalmic Pathology
Chapter 4: Wound Repair
Wound Repair in Specific Ocular Tissues
The conjunctiva is composed of nonkeratinized stratified squamous epithelium with goblet cells overlying a stroma called the substantia propria. The substantia propria is composed of blood vessels, lymphatic channels, and collagen fibers that are randomly distributed in a relatively loose configuration. In response to a wound, activated platelets form hemostatic plugs within the vessels, and neutrophils migrate to the surface of the wound edges (see Fig 4-1). The epithelium migrates to cover the wound. Meanwhile, stromal fibroblasts begin to proliferate and deposit fibronectin at the wound edges. Fibroblasts and blood vessels enter the wound and lay down new collagen. The final phase of remodeling is associated with canalization of new blood vessels and scarring due to contraction of collagen.
Figure 4-2 A full-thickness corneal wound (arrows) from cataract surgery. Note the mild hypercellularity of the wound due to fibrosis. There are no blood vessels in or around the wound.
(Courtesy of Nasreen A. Syed, MD.)
Figure 4-3 Clear corneal wound. 1, Tears carry neutrophils (white cells) with lysozymes to the wound within an hour. 2, Immediately after closure of the incision, the wound edge shows early disintegration and edema. The glycosaminoglycans at the edge are degraded. The nearby keratocytes are activated. 3, At 1 week, migrating epithelial and endothelial cells partially seal the wound; keratocytes begin to migrate and supply collagen and fibronectin. 4, Fibrocyte activity and collagen and matrix deposition continue. The endothelium, sealing the inner wound, lays down a new layer of Descemet membrane. 5, Epithelial regeneration is complete. Keratocytes fill the wound with type I collagen and repair slows. 6, The final wound contracts. The collagen fibers are not parallel with the surrounding lamellae, resulting in a wound that appears microscopically as scarring and clinically as an opacity. The number of keratocytes decreases.
(Illustration by Cyndie C. H. Wooley.)
Excerpted from BCSC 2020-2021 series: Section 4 - Ophthalmic Pathology and Intraocular Tumors. For more information and to purchase the entire series, please visit https://www.aao.org/bcsc.