ABMD (Anterior Basement Membrane Dystrophy), also known as epithelial basement membrane dystrophy (EBMD) or map-dot-fingerprint dystrophy, occurs primarily due to improper development and adherence of the corneal epithelium.
Understanding the Underlying Issue
The cornea, the clear front part of the eye, has several layers. The epithelium is the outermost layer, and it's crucial for protecting the eye and maintaining clear vision. In ABMD, the epithelium doesn't attach correctly to the underlying Bowman's layer and stroma (the main supportive tissue of the cornea). This faulty adhesion leads to several characteristic features:
- Abnormal Basement Membrane: The basement membrane, which anchors the epithelium, becomes thickened, irregular, and duplicated.
- Epithelial Instability: The epithelium becomes loose and prone to recurrent erosions (small breaks in the epithelial surface).
- Abnormal Cell Shedding: Cells don't shed and regenerate correctly, leading to build-up and structural abnormalities.
Specific Factors Contributing to ABMD
While the precise cause of ABMD is not fully understood, several factors are thought to contribute:
- Genetic Predisposition: ABMD often runs in families, suggesting a genetic component. Specific gene mutations are likely involved, but they haven't been fully identified.
- Epithelial Trauma: Minor injuries to the cornea, such as from contact lens wear or scratches, can trigger or worsen ABMD. The healing process can be disrupted, leading to improper basement membrane formation.
- Age: ABMD is more common in adults, particularly those over 40, indicating that age-related changes in the cornea may play a role.
- Other Corneal Conditions: ABMD can sometimes occur in conjunction with other corneal dystrophies or conditions.
Visual Representation
| Feature | Description |
|---|---|
| Maps | Grayish, irregular patches resembling coastlines |
| Dots | Small, opaque, whitish dots |
| Fingerprints | Fine, curved lines resembling fingerprints |
| Recurrent Erosions | Painful episodes of epithelial breakdown |
Symptoms
Symptoms of ABMD vary widely. Some individuals have no symptoms, while others experience:
- Blurry vision
- Glare or halos around lights
- Eye pain, especially upon waking
- Foreign body sensation
- Light sensitivity (photophobia)
- Tearing
In Summary
ABMD arises from a faulty epithelial basement membrane leading to poor adhesion of the corneal epithelium. While a definitive single cause remains elusive, genetic predisposition, corneal trauma, and age-related changes are all considered contributing factors.
