The limbus plays an important role in immune-mediated corneal disorders. The limbus has a population of antigen-presenting cells (APCs) that constitutively express MHC class II antigens and are capable of efficient mobilization and induction of T-cell responses. Therefore, immune-related corneal changes often occur in a peripheral location adjacent to the limbus. In addition, because the peripheral cornea is adjacent to the vascularized (posterior) limbus, circulating immune cells, immune complexes, and complement factors tend to deposit adjacent to the terminal capillary loops of the limbal vascular arcades, thereby producing a variety of immune phenomena that manifest in the corneal periphery. Predisposing factors include
Marginal infiltrates (also referred to as catarrhal infiltrates) are creamy white elliptical opacities typically separated from the limbus by a relatively lucent zone. They most often occur near the point of intersection of the eyelid margin and the limbus, that is, at 10, 2, 4 and 8 o’clock (see Chapter 3, Fig 3-19). In chronic disease, superficial blood vessels may cross the clear interval into the area of corneal infiltration. The epithelium overlying marginal infiltrates may be intact, show punctate epithelial erosions, or be ulcerated. Stromal opacification, peripheral corneal thinning, and/or pannus may develop following resolution of the acute marginal infiltrates. The management of marginal infiltrates is discussed in Chapter 3.
Ozcura F. Successful treatment of Staphylococcus-associated marginal keratitis with topical cyclosporine. Graefes Arch Clin Exp Ophthalmol. 2010;248(7):1049–1050.
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.