enhance the release of the impregnated calcium. If used at all, scraping should be gentle so as to prevent damage to the Bowman layer. A fibrous pannus may be present along with extensive calcific band keratopathy, especially if silicone oil is responsible, and neither EDTA nor scraping will remove such fibrous tissue. A soft contact lens can be helpful postoperatively until the epithelium has healed. The problem can recur but may not do so for years, at which time the treatment may be repeated. PTK using an excimer laser is not advised as a primary treatment because calcium ablates at a different rate from stroma and thus could produce a severely irregular surface. If residual opacification remains after the initial EDTA chelation, then PTK may be employed.

Jhanji V, Rapuano CJ, Vajpayee RB. Corneal calcific band keratopathy. Curr Opin Ophthalmol. 2011;22(4):283–289.

Stromal Degenerations

White limbal girdle of Vogt

Two forms of the white limbal girdle of Vogt have been described. Type I is a narrow, concentric, whitish superficial band running along the limbus in the palpebral fissure and is generally thought to represent early calcific band keratopathy. A lucid interval appears between the limbus and the girdle. This girdle is a degenerative change of the anterior limiting membrane, with chalklike opacities and small clear areas like the holes in Swiss cheese. Type II consists of small, white, flecklike, and needlelike deposits that are often seen at the nasal and temporal limbus in older patients. No clear interval separates this girdle from the limbus. Histologically, there is epithelial elastotic degeneration of collagen, sometimes with particles of calcium.

Corneal arcus

Corneal arcus, or arcus senilis, is most often an involutional change modified by genetic factors. However, arcus is sometimes indicative of a hyperlipoproteinemia (involving low-density lipoproteins) with elevated serum cholesterol, especially in patients younger than 40 years (see Chapter 11). It can be a prognostic factor for coronary artery disease in this age group. Arcus occurs occasionally as a congenital anomaly (arcus juvenilis), usually involving only a sector of the peripheral cornea not associated with abnormalities of serum lipid.

Arcus is a deposition of lipid in the peripheral corneal stroma. It starts at the inferior and superior poles of the cornea and in the late stages involves the entire circumference. The incidence is 60% in individuals between the ages of 50 and 60; it approaches 100% in individuals older than 80 years. The frequency is higher in the black population. The arcus has a hazy white appearance, a sharp outer border, and an indistinct central border; it is denser superiorly and inferiorly (Fig 12-9). A lucid interval is usually present between the peripheral edge of the arcus and the limbus. The lipid is found to be concentrated mainly in 2 areas of the peripheral corneal stroma: one adjacent to Bowman layer and another near Descemet membrane. Unilateral arcus is a rare condition associated with contralateral carotid artery disease or ocular hypotony. Arcus is also seen in Schnyder corneal dystrophy.

Figure 12-9 Corneal arcus. (Courtesy of Robert W. Weisenthal, MD.)

Crocodile shagreen

Anterior crocodile shagreen, or mosaic degeneration, is a central bilateral corneal opacity at the level of Bowman layer characterized by mosaic, polygonal, gray opacities separated by clear zones. Histologically, the Bowman layer is thrown into ridges and may be calcified. Posterior crocodile shagreen shows similar changes in the deep stroma near Descemet membrane.

Cornea farinata

Cornea farinata, an involutional change, is probably dominantly transmitted. The deep corneal stroma shows many subtle dot-shaped and comma-shaped opacities (Fig 12-10), which are often best seen in retroillumination. The deposits may consist of lipofuscin, a degenerative pigment that appears in some aging cells. The condition does not affect vision and has no clinical significance, except that it is sometimes mistaken for a progressive dystrophy. Pre-Descemet corneal dystrophy is most likely related, but it is unclear whether the conditions are degenerations or dystrophies.

Figure 12-10 Cornea farinata. (Courtesy of Robert W. Weisenthal, MD.)

Polymorphic amyloid degeneration

Polymorphic amyloid degeneration is a bilaterally symmetric, slowly progressive corneal degeneration that appears late in life. The corneal opacities emerge as either stellate flecks in midto deep stroma or irregular filaments. The two forms may occur together, but usually one predominates. These deposits are usually axial, polymorphic, and filamentous. The opacities are gray to white and

somewhat refractile but appear translucent in retroillumination (Fig 12-11). The intervening stroma appears clear, and visual acuity is usually normal. The corneal deposits consist of amyloid and can resemble some of the deposits seen in early lattice corneal dystrophy type 3. There is also an acquired (secondary localized) corneal amyloidosis, which may be associated with corneal inflammation (eg, trachoma, leprosy [Hansen disease], phlyctenulosis) or intraocular disease (eg, uveitis, retinopathy of prematurity) or may be secondary to trauma. Clinically, amyloid deposits in acquired corneal amyloidosis can appear as raised, yellow-pink nodular masses in the cornea or be nonspecific. Conjunctival amyloidosis may also be infiltrative. See the discussion on amyloidosis in Chapter 11. In addition, amyloid deposits of the conjunctiva are described in BCSC Section 4, Ophthalmic Pathology and Intraocular Tumors.

Figure 12-11 Polymorphic amyloid degeneration. (Courtesy of Robert W. Weisenthal, MD.)

Senile furrow degeneration

Senile furrow degeneration is an appearance of peripheral thinning in the lucid interval of a corneal arcus that is seen in older persons. Although slight thinning is occasionally present, it is usually more apparent than real. The epithelium is intact. There is no inflammation, vascularization, or tendency to perforate. Vision is rarely affected. No treatment is required.

Terrien marginal degeneration

The cause of Terrien marginal degeneration is unknown. This condition is a quiet, essentially noninflammatory, unilateral or asymmetrically bilateral, slowly progressive thinning of the peripheral cornea. Prevalence is roughly equal between the sexes, and cases usually occur in the second or third decade of life. The corneal thinning can be localized or involve extensive portions of the peripheral cornea.

Terrien marginal degeneration begins superiorly, spreads circumferentially, and in rare cases involves the central cornea or inferior limbus. The central wall is steep, and the peripheral wall slopes gradually. The epithelium remains intact, and a fine vascular pannus traverses the area of stromal thinning. A line of lipid deposits appears at the leading edge of the pannus (central edge of the furrow) (Fig 12-12). Spontaneous perforation is rare, although it can easily occur with minor trauma. Ruptures in Descemet membrane can result in interlamellar fluid or even a corneal cyst. Corneal topography reveals flattening of the peripheral thinned cornea, with steepening of the corneal surface approximately 90° away from the midpoint of the thinned area. This pattern usually results in high against-the-rule or oblique astigmatism.

Figure 12-13 A, Salzmann nodule in the paracentral cornea. B, Slit-lamp biomicroscopy showing an elevated nodule. C,

View of the lesion using fluorescein dye and a cobalt blue filter. (Courtesy of Cornea Service, Paulista School of Medicine, Federal University of São Paulo.)

Corneal keloid

Corneal keloids are white, superficial, and sometimes protuberant glistening corneal masses that can eventually involve the entire corneal surface. They are thought to be secondary to a vigorous fibrotic response to corneal injury or chronic ocular surface inflammation. Keloids can be congenital or primary, and they have been reported in association with many congenital conditions, such as Lowe syndrome. They have sometimes been confused with hypertrophic scars, Salzmann degeneration, or dermoids. Treatment of symptomatic patients may include superficial keratectomy or penetrating or lamellar keratoplasty.

Vanathi M, Panda A, Kai S, Sen S. Corneal keloid. Ocul Surf. 2008;6(4):186–198.

Lipid keratopathy

In lipid keratopathy, yellow or cream-colored lipids containing cholesterol, neutral fats, and glycoproteins are deposited in the superficial or deeper cornea, usually after prolonged corneal inflammation with scarring and corneal vascularization (eg, herpes simplex or herpes zoster keratitis, trachoma). This form is best described as secondary lipid keratopathy (Fig 12-14). In rare instances, lipid keratopathy has been reported with no evidence of an antecedent infection, inflammatory process, or corneal damage. These cases are best described as primary lipid keratopathy. Treatment is indicated in cases of compromised cosmetic appearance or decreased vision. This keratopathy should be differentiated from Schnyder corneal dystrophy, a rare autosomal dominant stromal dystrophy that is characterized by bilateral corneal opacification resulting from an abnormal accumulation of cholesterol and lipid. Argon laser treatment with and without fluorescein, photodynamic therapy with verteporfin, and subconjunctival and topical bevacizumab have been reported to reduce corneal neovascularization and lipid deposition.