Managing Three Major Stromal Dystrophies
BY WILLIAM L. MILLER, OD, PHD, FAAO
Continuing in my series on corneal dystrophies, we'll take a global look at stromal dystrophies. Many different types and variants of stromal dystrophies exist and have been linked to various genetic and metabolic alterations. The inheritance pattern for this entire group of dystrophies is almost evenly split between autosomal recessive and autosomal dominant.
The three major stromal dystrophies include granular, macular and lattice. Macular dystrophy tends to have the worst prognosis and is the rarest of the three. It is also an autosomal recessive dystrophy while the other two are autosomal dominant.
A great deal of genetic work has been accomplished in the area of stromal dystrophies. This work has mapped granular and lattice dystrophy to 5q31 and macular to 16q22. The general appearance of each of the three is related to their respective appearance with biomicroscopy as discrete, pleomorphic or linear opacities.
The histopathological profile for granular, macular and lattice dystrophies is different and is comprised of hyaline, glycosaminoglycan and amyloid deposits, respectively.
All three major stromal dystrophies appear around the first decade of life but may not exhibit symptoms until later, in some cases the second and third decade of life. A decrease in visual acuity occurs first in macular cases (first and second decade) followed by lattice (second and third) and lastly in granular cases (fourth and fifth).
Other signs and symptoms include glare complaints, photophobia and recurrent corneal erosions. Corneal erosions aren't typically seen in granular dystrophy but are more common in macular and very common in lattice. Macular dystrophy, unlike lattice and granular, may also demonstrate corneal thinning.
Treatment options are mainly aimed at controlling recurrent corneal erosions. Bandage contact lenses approved for continuous wear may help protect the corneal surface. As discussed in previous columns, a hyperosmotic agent such as Muro 128 (Bausch & Lomb) may also be used to promote epithelial adhesion.
Other treatments may include anterior stromal puncture and debridement, both of which are aimed at treating the recurrent corneal erosions that are secondary to the stromal dystrophy. In some cases the surface may become irregular from the underlying opacities and a large-diameter GP lens may be indicated to facilitate visual performance by creating a lacrimal lens, thus negating the effects of these surface irregularities. However, make sure that there are no harsh bearing areas, which would exacerbate recurrent corneal erosion formation.
One way to facilitate this type of fitting relationship is to prescribe a scleral or mini-scleral design that rests on conjunctival instead of corneal tissue. Some practitioners avoid GP lenses and opt for high-modulus silicone hydrogel lenses instead, which allow local corneal irregularities to be neutralized, yet minimize the frictional forces between the contact lens and cornea. Tinted cosmetic soft contact lenses may also be suitable for your stromal dystrophy patients who complain of photophobia and/or glare.
In more severe cases a penetrating keratoplasty may be performed. However, the specific stromal dystrophy may reappear in the graft over time. Other surgical procedures include a deep anterior lamellar keratoplasty or phototherapeutic keratectomy. CLS
Dr. Miller is the Director, Cornea and Contact Lens Service at the University of Houston College of Optometry. He is a member of the American Optometric Association and serves on its Journal Review Board. You can reach him at firstname.lastname@example.org.