Anterior basement membrane dystrophy (ABMD), also known as epithelial basement membrane dystrophy (EBMD) and map-dot-fingerprint (MDF) dystrophy, is the most common corneal dystrophy and may affect visual acuity and cause recurrent erosions. The abnormal adhesion of the corneal epithelial cells results in focal thickening and opacities, sometimes with subepithelial fibrosis. These areas may change in size and location and do affect vision if located within the visual axis. Approximately 10% of individuals with this dystrophy develop recurrent erosion syndrome (RES) with episodic attacks of varying frequency and severity.
Diagnosis
- Slit-lamp: signs can be mild and asymmetric with only a few visible dots, rather than the characteristic signs of obvious map lines, dots, and fingerprints. Subtle epithelial irregularities can best be observed with retro-illumination when the pupil is dilated or as areas of negative fluorescein staining.
- Topography: the corneal abnormalities produce irregular mires and focal topographic irregularities (asymmetric steep areas).
Treatment
Treatment is recommended when the condition affects the visual axis (causing reduced vision or inaccurate keratometry measurements prior to cataract or refractive surgery) or results in RES.
- Affecting visual axis: simple epithelial debridement and a bandage contact lens for 1-2 weeks, then serial refraction, keratometry, and/or topography measurements until stable.
- RES: Acutely, treat as corneal abrasion with topical antibiotic, cycloplegia, analgesia, and pressure patch or a bandage contact lens. Once healed, conservative medical treatment with lubricating eye drops and 5% sodium chloride ointment at bedtime for up to 1 year is typically not successful for RES due to ABMD. A surgical option is usually required:
- Superficial keratectomy (epithelial debridement): it is important to remove all of the abnormal epithelium.
- Superficial keratectomy with diamond burr polishing of Bowman’s membrane: may be as effective as PTK.
- Anterior stromal puncture (epithelial reinforcement) with a needle or Nd:YAG laser: treatment area should be 1-2mm beyond the edge of the abnormal epithelium to decrease the risk of recurrence. Treatment in the visual axis is often well tolerated by the patient but usually avoided by the physician because of the risk of scarring.
- Phototherapeutic keratectomy (PTK): this procedure also carries a risk of scarring in the visual axis as well as a hyperopic shift. Since only a small number of laser pulses are applied, these are rare complications. In my experience, PTK is the most successful option, and I usually proceed directly to this treatment in severe cases of RES.