procedures are shown in their corresponding sections.
Table 6-1
Figure 6-2 Congenital hereditary endothelial dystrophy. A, Clinical appearance with bilateral corneal clouding. B, Note diffuse edema, with bullous keratopathy (arrow). The Descemet membrane is diffusely thickened, without guttae, and endothelial
cells are absent. (Courtesy of Hans E. Grossniklaus, MD.)
Congenital Anomalies
Congenital Hereditary Endothelial Dystrophy
There are 2 forms of congenital hereditary endothelial dystrophy (CHED), with both forms causing bilateral corneal edema. The autosomal recessive form, the more common of these, is apparent at birth, accompanied by nystagmus, but nonprogressive. The autosomal dominant form is apparent within the first few years of life, not accompanied by nystagmus, but progressive (Fig 6-2A). The genetic loci for the autosomal dominant and recessive forms of CHED have been mapped to 20p11.2- q11.2 and 20p13, respectively. Despite their clinical differences, the 2 forms of CHED appear similar histologically. The corneal stroma is diffusely edematous, accounting for the marked increase in thickness observed clinically. The Descemet membrane appears thickened, without guttae (Fig 6-2B). Endothelial cell loss may be diffuse or focal. The histologic findings overall are very similar to those seen in pseudophakic/aphakic bullous keratopathy. The primary abnormality in CHED is thought to be a degeneration of endothelial cells during or after the fifth month of gestation. No systemic abnormalities are consistently associated with CHED. See also BCSC Section 8, External Disease and
Cornea.
Klintworth GK. The molecular genetics of the corneal dystrophies—current status. Front Biosci. 2003;8:d687–713.
Figure 6-3 Posterior polymorphous dystrophy. A, Clinical appearance, showing nummular opacities (arrows) on the endothelial surface. B, Note multilayering of endothelial cells (arrow). (Part A courtesy of Andrew J.W. Huang, MD; part B courtesy of
George J. Harocopos, MD.)
Posterior Polymorphous Dystrophy
Posterior polymorphous dystrophy (Fig 6-3) is another endothelial dystrophy that may be inherited in autosomal dominant or recessive fashion, with the mutation mapped to 20q11. In this condition, the endothelium has epithelial-like characteristics. These include multilayering, which may be seen histologically on routine light microscopy, and microvilli, which are best demonstrated on electron microscopy. The total number of endothelial cells may be decreased. Variable thickening of the Descemet membrane and guttae may be observed. There may also be secondary glaucoma, either open-angle or associated with iridocorneal adhesions. The resultant corneal clouding is typically central, but the degree of opacification varies greatly, with some patients never requiring corneal transplantation and others requiring keratoplasty in childhood or even infancy. See also BCSC Section 8, External Disease and Cornea.
Dermoid
Dermoid, a type of choristoma that may involve the cornea, is discussed in Chapter 5 (Fig 5-2). Dermoids are typically located at the limbus but may involve the central cornea. See also BCSC Section 6, Pediatric Ophthalmology and Strabismus.
Peters Anomaly
Peters anomaly represents the more severe end of the spectrum of anterior segment dysgenesis syndromes, in which neural crest migration, with respect to angle development and cleavage of the
lens from the corneal endothelium, does not occur properly. This anomaly is typically bilateral and sporadic, although autosomal dominant and recessive modes of inheritance have also been reported. In this anomaly, there is a localized defect in the central or paracentral portion of the Descemet membrane, known as internal ulcer of von Hippel, at the edges of which, typically, are iris strands adherent to the posterior corneal surface. In the most severe form of Peters anomaly, the lens is also adherent to the posterior corneal surface. These defects result in variable degrees of corneal clouding, often requiring corneal transplantation (Fig 6-4).
A related entity in the spectrum of anterior segment dysgenesis syndromes is sclerocornea. Whereas the corneal clouding in Peters anomaly is central, the clouding in sclerocornea is typically peripheral, although it may involve the entire cornea. The limbus is usually poorly defined, and vessels that are extensions of scleral, episcleral, and conjunctival vessels extend across the cornea. The most common ocular association is cornea plana, found in 80% of cases. Histologically, stromal vascularization and disorderly stromal lamellae of variable thickness may be present, correlating with the peripheral clouding seen clinically. Histologic findings similar to those of Peters anomaly are typically present. See also BCSC Section 8, External Disease and Cornea, and Section 6, Pediatric Ophthalmology and Strabismus.
Figure 6-4 Peters anomaly. A, Clinical appearance. Note the central corneal opacities, diffuse corneal clouding, and vascularization. B, PAS stain demonstrates internal ulcer of von Hippel. The Descemet membrane trails off at the edge of the internal ulcer (arrow). Iris tissue (to the right of the arrow) adheres to the posterior corneal surface at the edge of the