Amniotic Membrane for Glaucoma Surgeries

Glaucoma accounts for over 12% of all global blindness. It is an increase in pressure in the eye that damages the eye’s optic nerve. The optic nerve is what sends images to your brain, so glaucoma can cause permanent vision loss and even blindness. Glaucoma is progressive.

Diagram of eye showing fluid causing glaucoma that might be relieved with the help of amniotic membrane

Prevention
Glaucoma is influenced by genetics, and generally has no early symptoms. It is important to visit your eye doctor regularly, since once lost, vision cannot be restored. Older people are at higher risk, although anyone can suffer from glaucoma. People with risk factors like family history or diabetes may need to visit a doctor more than annually.

Trabeculectomy procedure
Although it will not restore vision already lost, a trabeculectomy (glaucoma filtration surgery) can lower the intraocular pressure and therefore prevent further damage. The procedure is usually performed under local anesthesia delivered with eye drops and injections around the eye. The surgeon makes a small hole in the sclera, or eye wall, which is covered by a flap, or trap door. Inside the eye is aqueous humor. The buildup of this fluid, which differs from tears, is what causes pressure on the optic nerve and damage to the eye. With the trabeculectomy surgery, the fluid can drain through the trap door to a bleb, which is a small blister-like spot underneath the upper eyelid that is not visible just by looking at the eyes. Then the trap door is sutured so the fluid does not drain too quickly. There are potential complications, including fibrosis (scarring). Mitomycin C, a drug originally used to treat cancer, has been used to reduce scarring, but doctors have searched for something more effective. They may have found that trabeculectomy with amniotic membrane is better for the patient.

Wound healing is the most important factor in the success of glaucoma surgery. There are several risk factors in healing that could be improved from existing glaucoma filtration surgery: inflammation; fibrin formation, growth factors and cytokines. Amniotic membrane has been shown to be very effective with wound healing and to heal the eyes in general. Numerous studies have demonstrated a significant antifibrotic effect. It is also anti-inflammatory, antiangiogenic, and antimicrobial. For that reason, it has been used to treat other eye conditions like bullous keratopathy. Amniotic membrane for glaucoma might be promising as an adjuvant as well. Fibroblast proliferation is important to tissue repair because fibroblasts produce structural proteins and stimulate angiogenesis and epithelialization. Amniotic membrane acts as a scaffold for fibroblast proliferation to occur.

Trabeculectomy with Amniotic Membrane Studies
Stavrakas et al. set out to determine the effects of using amniotic membranes in trabeculectomies. In the study, 32 eyes underwent trabeculectomy with amnion shield, and 27 eyes underwent the procedure without any such supplement. The amniotic membrane was used as a patch with no sutures. After 24 months, the study group had 61% less risk of developing intraocular pressure than the control group, with no major complications.
In another study of 19 eyes where each had been through at least one failed trabeculectomy, researchers found that amniotic membrane transplantation was safe and useful for improving surgical outcomes and maintaining low postoperative interocular pressure. And finally, another study found that, as an alternative tissue, there was an improvement in bleb survival when amniotic membrane for glaucoma was used.

Glaucoma Shunt Surgery
When laser treatment is not sufficient, doctors may install an Ahmed Valve, or glaucoma drainage valve. In a study to determine whether amniotic membrane grafts are effective in glaucoma drainage device surgery, the results were positive. After the surgery, the tube is exposed, leading to the potential for infection. Infection could cause blindness. Amniotic membrane can prevent infection by molding around the tube.
The study also found that amniotic membrane for glaucoma does not thin or melt over time, but maintains its thickness and protection. Unlike other materials like pericardial grafts or scleral patch grafts, amniotic membrane is translucent, allowing doctors to easily diagnose issues that need addressing early, like tube migration, retraction, kinking, and twisting.

Conclusion

Amniotic membrane may improve outcomes of trabeculectomies and glaucoma shunt surgery. If you think you may need glaucoma surgery, contact us to be connected to a doctor who can tell you if amniotic membrane can help.

References
https://journals.lww.com/glaucomajournal/Abstract/2015/02000/Amniotic_Membrane_Transplantation_in_Failed.13.aspx
https://www.nature.com/articles/eye2008410#Tab1
https://www.ncbi.nlm.nih.gov/pubmed/9599369
https://www.ncbi.nlm.nih.gov/pubmed/17083539
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3280101/#b27-opth-6-205
https://www.ncbi.nlm.nih.gov/pubmed/21563743