H18.11-13 Bullous Keratopathy

Bullous keratopathy occurs as the result of severe and prolonged corneal edema.  The condition occurs when an influx of fluid into the cornea overwhelms the corneas ability to remove the excess fluid.  As fluid accumulates in the more anterior layers of the cornea, blisters and epithelial bullae develop. 

Bullous keratopathy may occur in any of the following conditions:

• Fuchs’ endothelial dystrophy
• Posterior polymorphous endothelial dystrophy

Most commonly, bullous keratopathy occurs as a unintended consequence of intraocular surgeries:

• Pseudophakic bullous keratopathy in a 70-year-old male

Structural Damage to the Eye

The layers of the cornea are optically transparent so that the entire structure can transmit visible light.  When viewed in cross-section, the cornea is a basic structure of two covering layers with a central collagen stroma.  The outer covering layer is called the anterior cornea.  It is composed of the corneal epithelium and a basement membrane called Bowman’s membrane.  This layer functions as a semi-permeable membrane that keeps pathogens out of the eye but allows nutrients from the pre-ocular tear film to nourish the anterior cornea.

The middle layer of the cornea is called the stroma.  This layer comprises over 90% of the cornea’s thickness and is composed of tightly packed collagen fibrils in an orderly lamellar arrangement.  The spacing and arrangement of the fibrils makes the corneal stroma optically transparent.  To maintain optical transparency, the stroma must be maintained in a state of relative deturgescence and the normal level of stromal hydration is 78% water.  The inability to maintain stromal deturgescenece can result in corneal edema and a loss of stromal transparency.

The inner covering layer is called the posterior cornea.  It is composed of the corneal endothelium and Descemet’s membrane.  This layer fuctions as a semi-permeable membrane that controls fluid and solute transport across the posterior surface of the cornea.  Because of the strength and flexibility of Descemet’s membrane, the posterior cornea also serves as a barrier against injury.

Functional Damage to the Eye

• Decreased visual acuity secondary to epithelial edema
• Epithelial edema produces irregularities in the corneal refractive surface
• At night, with the eye closed, epithelial edema worsens due to a hypertonic environment
• Decreased vision is usually worse in the morning hours
• In advanced stages, bullae (water blister) formation can cause significant ocular pain when they burst

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

• Determine the underlying condition producing the bullous keratopathy
• Relieve ocular discomfort 
• Prevent complications that occur with epithelial defects (i.e., infection, uveitis)
• Improve visual acuity

Patient History

Patients will usually present with the following symptoms and/or clinical history:

• Blurred vision
• Eye pain
• Foreign body sensation
• Sensitivity to bright light
• Epiphora
• History of pre-existing corneal disease
• History of previous ocular surgery (especially cataract surgery)

External Ocular Examination with Biomicroscopy

• Loss of stromal transparency
• Folds in Descemet’s membrane
• Obvious thickening of the cornea
• Epithelial blisters and bullae
• Loss of corneal luster

DIAGNOSTIC TESTS

External Ocular Photography

• To document the progress or lack of progress of bullous keratopathy
• To help plan a treatment program
• To document the delivery of the medical treatment
• To document the response to treatment

Because bullous keratopathy can be caused by various eye diseases and conditions and the disease may be classified according to its cause. 

None.  Possibly very advanced recurrent corneal erosion but an erosion typically does not produce large bullae and erosions have more intermittent symptoms.

Because corneal edema can be caused by various eye diseases and conditions, the condition is treated according to the cause. The first goal of treating patients with corneal edema is to reduce the edema and the associated symptoms of blurred vision and ocular discomfort.  Second, best practices treatment guidelines indicate treatment of the underlying condition producing the corneal edema.

Preventative Treatment

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

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