Approach Considerations
Family history and clinical examination are typically sufficient to make the correct diagnosis of lattice corneal dystrophy.
While the genetic basis of lattice corneal dystrophy is known, genetic studies are not commonly used clinically.
Imaging of the cornea with anterior segment optical coherence tomography (OCT) can demonstrate the extent and depth of amyloid deposits and may assist with diagnosis or treatment planning.
Corneal biopsy is not routinely required in the diagnosis of lattice dystrophy; however in the case of corneal biopsy, diagnosis can be made based on histochemical staining and polarization microscopy. Patients with lattice dystrophy type II (systemic amyloidosis) need further workup with the appropriate specialist owing to involvement of the skin, nerves, arteries, and other organs.
Laboratory Studies
A genetic analysis can determine the specific mutation on the TGFBI (BIGH3) gene of chromosome 5, which can allow for the precise diagnosis of the subtype of lattice corneal dystrophy and can be useful for differentiating lattice corneal dystrophy from Avellino dystrophy, granular dystrophy, and Reis-Bückler dystrophy (all which have mutations of the TGFBI,or BIGH3, gene). This, however, is not routinely used clinically at this time.
Procedures
Corneal biopsy, which is not clinically indicated, reveals amyloid in the corneal stroma.
Histologic Findings
Lattice corneal dystrophy is an amyloidosis of the corneal stroma. In lattice dystrophy type I, the source of the amyloid is believed to be localized intracellular production. Histologically, a layer of amyloid and collagen separates the epithelial basement membrane from the Bowman layer. In addition, linear deposits of amyloid fibrils are seen within the corneal stroma, disrupting the regular arrangement of corneal lamellae. Amyloid deposits stain orange with Congo red. They also demonstrate green birefringence under a polarizing filter. Amyloid is a noncollagenous fibrous protein of variable makeup in different forms of amyloidosis. [13]
Imaging Studies
Anterior segment optical coherence tomography (OCT) may be used to measure the depth of the corneal opacities. This can be useful in guiding treatment, particular when considering phototherapeutic keratectomy for the removal of superficial opacities. [16]
Other Tests
Corneal esthesiometry is used to measure tactile sensation at the surface of the cornea. Because lattice dystrophy is associated with decreased corneal sensation, esthesiometry may be of clinical interest. Whether decreased corneal sensitivity is associated with increased morbidity in lattice corneal dystrophy is unknown.
Staging
A staging system for lattice corneal dystrophy is not commonly used at this time.
-
Lattice corneal dystrophy. Image courtesy of James J. Reidy, MD, FACS, Associate Professor of Ophthalmology, State University of New York, School of Medicine & Biomedical Sciences, Buffalo, New York.
-
Slit lamp image of lattice corneal dystrophy. Image courtesy of James J. Reidy, MD, FACS, Associate Professor of Ophthalmology, State University of New York, School of Medicine & Biomedical Sciences, Buffalo, New York.
Tables
Feature |
Granular Dystrophy |
Macular Dystrophy |
Lattice Dystrophy |
|---|---|---|---|
Age of onset |
First decade of life |
First decade of life |
First decade of life |
Heredity |
Autosomal dominant |
Autosomal recessive |
Autosomal dominant |
Reduced vision |
Fourth or fifth decade of life |
First or second decade of life |
Second or third decade of life |
Erosions |
Uncommon |
Common |
Frequent |
Opacities |
Discrete, intervening stroma Clear, not to limbus |
Indistinct margins, intervening Stroma hazy, extends to limbus |
Refractile lines and dots Usually not to limbus |
Material |
Hyaline |
Glycosaminoglycans |
Amyloid |
