“salmon patch” appearance of a lymphoid lesion (discussed later). Histologically, amyloid appears as eosinophilic, extracellular deposits within the stroma, sometimes demonstrating a perivascular distribution. On Congo red stain, under standard light, amyloid deposits appear orange; but when viewed with polarized light and a rotating polarization filter, they exhibit birefringence with dichroism. That is, they change from orange to apple green as the filter is rotated. Other useful staining methods include crystal violet and the fluorescent stain thioflavin T. Electron microscopy shows characteristic fibrils (see Chapter 10, Fig 10-11). In localized amyloidosis, local clonal proliferations of plasma cells have been demonstrated, and it is thought that locally secreted monoclonal immunoglobulins are the precursors of biochemically identified immunoglobulinderived amyloid proteins. See Chapter 6 of this volume for examples of primary and secondary localized amyloidosis of the cornea and BCSC Section 8, External Disease and Cornea.

Kaplan B, Martin BM, Cohen HI, et al. Primary local orbital amyloidosis: biochemical identification of the immunoglobulin light chain κIII subtype in a small formalin fixed, paraffin wax embedded tissue sample. J Clin Pathol. 2005;58(5):539–542.

Figure 5-12 Pterygium. A, Clinical appearance. B, Histologically, a focus of elastotic degeneration is present (arrow), as well as prominent blood vessels (arrowheads), with surgically induced hemorrhage. C, In this case, the conjunctival and corneal portions of the pterygium are evident. Note the prominent blood vessels in the conjunctival portion (arrow), and the destruction of the Bowman layer by ingrowth of fibroconnective tissue in the corneal portion (arrowheads). (Part A courtesy of

Hans E. Grossniklaus, MD; parts B and C courtesy of George J. Harocopos, MD.)

Epithelial Inclusion Cyst

A conjunctival epithelial inclusion cyst may form at a site of prior accidental or surgical trauma (eg, after strabismus surgery, retinal surgery, or enucleation). Clinically, the lesion appears as a transparent, cystic elevation on the ocular surface. There may be associated injection (Fig 5-14). Histology shows a cystic space lined by conjunctival epithelium, located in the substantia propria. The lumen may be empty or may contain inspissated proteinaceous material and cellular debris.