The amniotic membrane (AM) is the innermost layer of the placenta, the tissue that surrounds and protects a fetus during development. This material is recovered after elective cesarean sections, and donors undergo rigorous screening for transmissible diseases before processing. Historically, the membrane was first used in medicine over a century ago for skin grafting. Today, it serves as a biological bandage or scaffold placed on the eye’s surface to aid in the healing of various corneal and conjunctival conditions.
Therapeutic Mechanisms and Delivery Methods
The fundamental purpose of applying the amniotic membrane is to create a nurturing environment for the damaged ocular surface to regenerate. This biological material contains specific growth factors and cytokines that actively promote epithelial cell migration and proliferation, which accelerates the repair of the cornea’s protective outer layer. The unique composition of the membrane also works to reduce inflammation by suppressing pro-inflammatory molecules like cytokines at the injury site.
Another significant mechanism is the membrane’s anti-scarring action, which involves inhibiting the activity of fibroblasts, the cells responsible for creating scar tissue. By limiting scar formation, the membrane helps maintain the clarity and transparency of the cornea. Furthermore, the material contains factors that discourage the growth of new, unwanted blood vessels onto the cornea, a process known as anti-angiogenesis.
The membrane is delivered to the eye using two primary methods, each suited to different clinical scenarios. The first involves securing the membrane as a surgical graft, typically using fine sutures or a medical-grade tissue adhesive like fibrin glue. This method is often used for more extensive or complex surface reconstructions.
The second, more common method for in-office procedures uses a sutureless delivery system, such as a self-retaining device. This device consists of a cryopreserved membrane secured within a flexible polycarbonate ring, which is inserted similarly to a large contact lens. For dehydrated membranes, a bandage contact lens is often placed over the graft to keep it securely positioned.
Expected Post-Procedure Ocular Reactions
Patients should anticipate temporary reactions immediately following the placement of the amniotic membrane, which are generally mild and self-limiting. The most frequently reported reaction is a foreign body sensation, often described as feeling like grit or sand persistently in the eye. This sensation is directly related to the physical presence of the membrane or its retaining ring.
Temporary blurring of vision is also a common experience, particularly when the membrane covers the central visual axis of the cornea. This blurring occurs because the membrane acts as a translucent film over the eye, scattering light until it dissolves or is removed. Patients are often advised to refrain from driving or activities requiring acute vision while the membrane is in place.
Mild discomfort, light sensitivity (photophobia), and increased tearing (epiphora) are also expected as the eye adjusts to the material and begins the healing process. If a ring-based device is used, the polycarbonate ring itself may cause a feeling of pressure or irritation beneath the eyelids. Standard over-the-counter pain relievers are usually sufficient to manage this temporary discomfort.
These reactions are part of the normal course of healing. They typically resolve as the membrane gradually breaks down and is absorbed by the eye, which usually occurs within a week or two.
Rare and Severe Adverse Events
While the amniotic membrane is considered a very safe treatment, there are rare but serious adverse events that require immediate medical attention. The most concerning risk is infectious keratitis, an infection of the cornea. Although the membrane is rigorously screened and processed with antibiotics to minimize this risk, any breach in sterile protocol or underlying patient susceptibility can lead to a serious infection.
Another potential issue is the premature loss or displacement of the graft from the ocular surface. This can happen if the membrane is not securely placed or if the patient rubs the eye, which can destabilize the material or the retaining ring. If the membrane dissolves too quickly, it may signal aggressive underlying inflammation, indicating that the initial therapeutic goal has not been met and a replacement may be required.
In cases where the underlying eye condition is severe, such as deep corneal ulcers or chemical burns, treatment failure remains a possibility. The membrane may not be sufficient to prevent the progression of tissue breakdown. In extremely rare instances, this can lead to serious complications like corneal perforation. This outcome is generally attributed to the severity of the original disease rather than the membrane itself.
Some patients may be prescribed topical steroid drops to manage post-procedure inflammation. A small percentage of individuals are sensitive to these drops, which can cause a temporary, but significant, elevation of pressure inside the eye.