H18.59 Anterior Corneal Dystrophies

Epithelial basement membrane dystrophy (EBMD) is characterized by abnormal quantities of basement membrane and cytoplasmic debris that are misdirected into the corneal epithelium.  Clinically, the abnormal deposits in EBMD appear as dot-like opacities, map-like patterns, or whorled fingerprint-like lines in the corneal epithelium.  In many patients, the epithelial lesions change in appearance, location and number over time.

• Normal appearance under low magnification
• Corneal opacities in EBMD under high magnification

The anterior layer of the cornea is composed of the corneal epithelium and its underlying basement membrane.  The basal cells of the corneal epithelium produce and adhere to the basement membrane via hemidesmosomes and basement membrane complexes.

Structural Damage to the Eye

In most patients, the disease causes no significant structural deficit to the cornea, no symptoms and no functional vision problems.  In patients with clinically significant EBMD, the abnormal deposits of basement membrane can result in the loss of hemidesmosomes between Bowman’s layer and the basal epithelial cells.  Over time, the loss of hemidesmosomes can lead to the following:

Functional Damage to the Eye

• Decreased vision may result if any structural damage occurs in the axial region of the cornea

The main goal of the diagnostic evaluation in a patient with EBMD is to accomplish the following:

In the vast majority of patients, EBMD is thought to be a degenerative disorder rather than a corneal dystrophy.

A small number of patients with EBMD have a true corneal dystrophy with a genetic inheritance pattern.  According to the International Committee for Classification of Corneal Dystrophies (IC3D), epithelial basement membrane dystrophy is a Categoy 1 Corneal Dystrophy.  In this type of dystrophy, the gene has been identified and mapped and specific mutations are known.

Differential diagnoses would include any diseases that present with corneal opacities or epithelial damage.

• Corneal abrasion 
• Fuchs’ endothelial dystrophy 
• Herpes simplex
• Herpes zoster 

The first goal of treating patients with EBMD is to reduce complications.

Preventative Treatment

• Avoiding or minimizing contact lens wear in patients with preexisting epithelial disease

Pharmocologic Treatment

Hyperosmotics

• The goal of treatment is to improve visual acuity by deturgescence of the stroma or epithelium. Compliance with topical hyperosmotic solutions can be challenging due to the burning sensations they often produce. Nighttime application of hyperosmotic ointment is an excellent if not preferred treatment.

Artificial Tears (FreshKote Ophthalmic Solution)

• The goal of treatment is to remove excess water from the epithelium by utilizing the high oncotic pressure of the solution

Mechanical Treatment

• Bandage contact lenses – in patients with EBMD, overnight wear of soft contact lens can be used to decrease pain and improve visual acuity

Surgical Treatment

• Amniotic membrane placement
• Debridement/superficial keratectomy
• Debride the cornea with a blunt Kimura spatula
• Smoothing the basement membrane with a diamond burr
• Excimer laser phototherapeutic keratectomy

Amniotic Membrane Inserts

		ProKera Amniotic Membrane Insert Cryopreserved amniotic membrane graft fastened to a thermoplastic symblepharon ring The device acts as a self-retaining biological bandage Promotes reepithelialization
BioDOptix Amniotic Membrane Insert Dehydrated amniotic membrane graft

It should be noted that the underlying pathophysiology of EBMD lies in the basement membrance.  Simple debridement of the epithelium does little to solve this problem, more likely just resetting the clock for future epithelial breakdown.  Polishing the basement membrane with a diamond burr or photoablative removal of the defective basement membrane will produce far more effective and longer lasting benefits.

1.  Bowling E.  Russell GE.  Shovlin JP.  Sindt CW.  Epithelial basement membrane dystrophy.  RevOptom:  The Cornea Atlas: 14.