Amniotic membrane has been shown to treat symptoms of pseudophakic bullous keratopathy, including pain.
Bullous keratopathy is a condition of the eye in which small vesicles, also called bullae, are formed on the cornea due to an imbalance in fluid forces. They are like blisters that can burst and release fluid on the eye. The prevention of proper fluid control in the eye leads to the cornea becoming less transparent. Corneal transparency is essential for effectively transmitting light so that we can see. The condition can be painful, and vision is impaired.
There are several potential causes of bullous keratopathy, such as Fuch’s disease, but most frequently it is from trauma stemming from cataract surgery. Cataract affects around 20 million people worldwide. In rare cases, around 1-2% of cataract surgeries (2-4 million), there can be trauma to the eye. With this trauma comes cell loss and endothelial and subepithelial decomposition. The epithelial bullae cause decreased vision, tearing, and pain. The condition can also cause light sensitivity (photophobia) and reflex lacrimation, the production of tears in response to irritation.
The cornea is responsible for refraction of the eye. It protects the rest of the eye by acting as a barrier. The cornea is transparent, with a high density of nerve endings. It has five layers, front to back, epithelium, Bowman’s layer, stroma, Descemet’s membrane, and endothelium. Endothelial cells are like gatekeepers of fluid in the stroma. They remove fluid that might obscure vision. This is essential to the cornea’s transparency.
Why does this rare complication of cataract surgery, bullous keratopathy occur?
More common in patients in their 60s, the high temperatures associated with the surgery, high irrigation or aspiration rates, phacoemulsification. The ultrasound can produce free radicals that can damage the corneal endothelium.
How can pseudophakic bullous keratopathy be treated?
Treatment for corneal edema has been topical agents (sodium chloride), anti-inflammatory drugs, topical or internal antiglaucoma medications, corticosteroids, lubricants, and therapeutic contact lenses. Systemic L-cysteine is another option. Conjuctival flaps are effective, but not cosmetically pleasing. Finally, anterior stromal puncture is common.
Another common treatment is corneal transplantation. The advantage is that is both symptom relief and actual improvement in eyesight. There are two main disadvantages. One is the risk of astigmatism. The second is the risk of rejection. There are high success rates, but any time there is a transplant, there is some risk, and rejection occurs in 5-30% of patients. Patients take anti-rejection drugs for varying period. Corneal collagen cross linking (CXL) can improve corneal transparency and thickness and ocular pain, but not for long terms.
The new frontier: amniotic membrane for eye pain
Amniotic membrane is donated by mothers giving informed consent. It is composed of a stroma, and a thick basal membrane. It is thought to contain growth factors that can re-ephitelialize. It is increasingly being used in a number of eye-related issues such as dry eye and corneal abrasion.
In 1999, Pires et al. used amniotic membrane in an attempt to relieve pain. 50 of 55 patients remained pain-free after 33 weeks following epithelial (debridement) and replacement with amniotic membrane. In another study, 88% were pain free after 25 months. Amniotic membrane from women who had given birth via caesarean section was tested for disease and frozen. The amniotic membrane was sutured to the eye. A small nylon suture was removed one week later. In 37 cases the symptoms improved, in 8 cases the minimum symptoms persisted, and in 29 cases the symptoms completely disappeared. In 5 cases, there were no significant improvements, symptoms reappeared briefly after membrane resorption. The theory is that protease inhibitors in the rich stromal matrix of the amniotic membrane promotes healing and reduces inflammation. Vision problems persist but pain is greatly reduced.
Amniotic membrane has been shown to be effective in controlling pain and does not induce neovascularization. There are no cosmetic issues after the procedures.
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By Jessie A. Arnold, M.A., J.D., Legal Advisor