124 CORNEAL DYSTROPHIES

hyperlipidemias, and serum lipid levels do not correlate with the density of the corneal opacities. The dystrophy more likely represents a localized defect in cholesterol metabolism.

Of importance, not all patients with Schnyder’s dystrophy have clinical evidence of corneal crystalline deposits.

Paparo LG, Rapuano CJ, Raber IM, et al: Phototherapeutic keratectomy for Schnyder’s crystalline corneal dystrophy. Cornea 19:343–347, 2000.

16. How does central cloudy dystrophy of Franc¸ois differ from posterior crocodile shagreen?

Although some physicians have argued that location of the lesions differs in the two conditions, the lesions are clinically the same. It is generally accepted that the polygonal ‘‘cracked-ice’’ lesions of the central cloudy dystrophy of Franc¸ois are more central, deeper, and, by definition, bilateral with an inheritance pattern. On the other hand, posterior crocodile shagreen is more commonly peripheral and anterior stromal and is classified as degeneration. Of importance, both conditions are associated with normal corneal thickness and no recurrent erosions or significant visual compromise.

17. What characterizes Avellino dystrophy?

Avellino dystrophy also has been called granular-lattice dystrophy. The granular deposits occur in the anterior stroma early in the progression of the condition, followed later by lattice lesions in the mid to posterior stroma and finally by anterior stromal haze. More patients with Avellino dystrophy experience recurrent erosions than patients with typical granular dystrophy. Recently, the disease-causing genes of lattice dystrophy type I, granular dystrophy, Avellino dystrophy, and Reis-Bu¨cklers dystrophy were mapped to chromosome 5q, suggesting one of the following possibilities:

1. A corneal gene family exists in this region.

2. These corneal dystrophies represent allelic heterogeneity (i.e., different mutations within the same gene manifest as different phenotypes).

3. They are the same disease.

18. How are stromal dystrophies treated?

To the extent that some dystrophies, such as lattice and Avellino, are associated with recurrent erosions, they are treated as discussed earlier. When the lesions obscure vision and are restricted to the anterior third of

the stroma, they are usually amenable to surgical lamellar or phototherapeutic keratectomy (PTK) with the excimer laser. If the lesions are deeper, lamellar or penetrating keratoplasty is necessary.

19. Is penetrating keratoplasty a definitive treatment?

In most instances, penetrating keratoplasty for stromal dystrophies is associated with recurrence of the pathology in the graft as early as 1 year

after surgery. The recurrent pathology

Figure 12-4. Appearance of eye after penetrating is sometimes milder than in the original keratoplasty.

cornea but requires regrafting not infrequently (Fig. 12-4.)

Dinh R, Rapuano CJ, Cohen EJ, Laibson PR: Recurrence of corneal dystrophy after excimer laser phototherapeutic keratectomy. Ophthalmology 106:1490–1497, 1999.