eMedicine Specialties > Ophthalmology > Cornea

Dystrophy, Granular

Author: William Trattler, MD, Miami Center for Excellence in Eye Care; Consulting Staff, Department of Ophthalmology, Miami Baptist Hospital
Coauthor(s): William Lloyd Clark, MD, Consulting Staff, Palmetto Retina; Natalie Afshari, MD, Assistant Professor, Cornea and Refractive Surgery, Department of Ophthalmology, Duke University Eye Center, Duke University Medical Center
Contributor Information and Disclosures

Updated: Mar 15, 2006

Introduction

Background

Granular dystrophy is an autosomal dominant, bilateral, noninflammatory condition that results in deposition of opacities in the cornea by adulthood. It specifically affects the middle portion of the cornea (stroma) and eventually can cause decreased vision and eye discomfort. Severe cases of granular dystrophy can be treated with either excimer laser ablation or by replacing cornea (corneal transplant).

Pathophysiology

The cornea is the clear outer coat of the front of eye. A dystrophy of the cornea is defined as a bilateral noninflammatory clouding of cornea. Corneal dystrophies can be divided into 3 categories based on their location within the cornea, as follows: (1) anterior corneal dystrophies affect the corneal epithelium and may involve the Bowman membrane; (2) stromal corneal dystrophies (which include granular dystrophy) affect the central layer of cornea, the stroma; and (3) posterior corneal dystrophies involve the Descemet membrane and endothelium.

Most corneal dystrophies have an onset prior to age 20 years (exceptions include map-dot-fingerprint dystrophy and Fuchs corneal dystrophy). Most corneal dystrophies are dominantly inherited, exceptions being macular dystrophy, type-3 lattice dystrophy, and the autosomal recessive form of congenital hereditary endothelial dystrophy.

Granular corneal dystrophy types I, II (Avellino dystrophy), have been reported to result from mutations in the BIGH3 gene. Depending on the specific mutation in the beta ig-h3 gene, the phenotypes of corneal dystrophy may differ.

Frequency

United States

Uncommon

International

Uncommon

Mortality/Morbidity

• Corneal changes generally first become visible during the second decade of life, but vision may not be affected until the fourth to fifth decade of life.
• Eye pain from recurrent corneal erosions also can occur.

Sex

No sexual predilection has been reported.

Age

Corneal changes usually become visible during the second decade of life, but patients may not be affected until the fourth to fifth decade of life.

Clinical

History

• Patients may have decreased vision, photosensitivity, and/or eye pain (from recurrent corneal erosions).
• Because granular dystrophy is autosomal dominant, it is likely that one of the parents will have granular corneal dystrophy as well.

Physical

• Granular dystrophy is characterized by bilateral formation of discrete, focal, white granular deposits in the anterior stroma of cornea with clear areas between these deposits.
  • The granules are located primarily in the central cornea, with an absence of these deposits in the peripheral cornea.
  • The deposits can resemble crushed breadcrumbs or snowflakes. As patients advance in age, the deposits become larger and increase in number. Eventually, the intervening clear areas develop a mild-to-severe corneal haze.
  • When there are clear spaces between the deposits, the vision generally is not affected severely. However, with time, the clear spaces become involved with opacity. This later onset opacity in the previously clear spaces is usually much more superficial than the longstanding, dense white granules. The vision declines dramatically when the clear spaces opacify.

Causes

Granular dystrophy is an autosomal dominant condition; its genetic defect has been mapped to chromosome 5q.

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