An artificial cornea, also known as a keratoprosthesis, is a synthetic replacement for the natural cornea, the transparent outer layer of the eye that focuses light. This medical device offers a path to restored vision for individuals with severe corneal damage, especially when traditional donor corneal transplants are not feasible or have failed.
Understanding the Artificial Cornea
An artificial cornea is a synthetic implant designed to replace a diseased or damaged natural cornea. This solution is considered for patients with severe corneal damage that cannot be effectively treated by conventional methods, such as standard donor corneal transplants. It is also an option when a patient’s body repeatedly rejects donor tissue, or if a donor cornea is not a viable option.
Conditions indicating the use of an artificial cornea include extensive corneal scarring from injuries, infections, or chemical burns. It is also an option for those with congenital defects, aggressive immune systems, or multiple failures with previous corneal grafts. The goal is to provide a clear optical pathway for light to reach the retina, restoring vision in challenging cases of corneal blindness.
How Artificial Corneas are Designed
Artificial corneas are engineered with specific designs and materials to function effectively within the eye. The most widely used device is the Boston Keratoprosthesis (KPro), which received FDA clearance in 1992. This device typically consists of two main parts: a clear optical cylinder made from polymethylmethacrylate (PMMA), a transparent plastic, and a back plate, often made of titanium, that secures the optical component. The Boston KPro is assembled by screwing the optical cylinder into the center of a supporting plate, and it is then implanted into a ring of donor corneal tissue for better integration.
Other designs include the AlphaCor, a bio-integrating keratoprosthesis made of a porous, hydrophobic material designed to integrate with surrounding tissue. The Osteo-Odonto-Keratoprosthesis (OOKP) is a more complex biological device that utilizes a patient’s own tooth and surrounding bone to support the artificial cornea. Newer innovations are exploring materials like hydrogels and nanomaterials to create more biocompatible and durable implants, aiming to mimic the natural cornea.
The Surgical Journey and Recovery
Artificial cornea implantation typically involves an outpatient surgical procedure, allowing patients to return home the same day. The surgery is often performed under local anesthesia, though general anesthesia may be used for infants and young children. The procedure generally takes about three hours, including preparation and recovery time.
During the surgery, the damaged corneal tissue is removed. The assembled artificial cornea, sometimes integrated with a donor corneal graft, is then sutured into place within the patient’s eye. Immediately following the operation, a soft contact lens is applied to the surface of the eye to protect the new artificial cornea. Patients receive post-operative instructions, including the use of eye drops to prevent infection and manage swelling, and may need to wear an eye shield. Patients are advised to avoid strenuous activities and refrain from bending below the waist for several weeks to ensure proper healing.
Long-Term Outlook and Management
After receiving an artificial cornea, patients can anticipate a period of adjustment as their vision improves over several weeks to months. Long-term management involves continuous follow-up care with an ophthalmologist, often with bi-monthly check-ups during the first year. Regular use of prescribed eye drops is necessary to prevent complications such as infection and glaucoma.
Patients should be aware of potential long-term complications. These can include the formation of a retroprosthetic membrane, which is a film that can develop behind the device and affect vision. Glaucoma, an increase in eye pressure, is also a concern and requires careful monitoring. Other potential issues include device extrusion, where the artificial cornea moves out of place, or corneal melt around the optic, which can lead to fluid leakage and infection. Ongoing vigilance and adherence to medical advice are important for maintaining eye health and the device’s longevity.