Introduction
The cornea is the clear, outermost layer of the eyes that plays an important role in focusing light into the eyes and providing a clear vision. If injured, swollen, scarred, or damaged, light will not focus properly on the eye, leading to vision impairment or blindness. Suppose the cornea cannot be healed or repaired. In that case, the ophthalmologist may recommend a corneal transplant, a surgical procedure where a damaged cornea is replaced with a healthy donor cornea. Different types of corneal transplants involve replacing only the front and middle layers of the cornea. In other cases, only the inner layer is removed and replaced. Sometimes, the entire cornea may be replaced. However, due to the scarcity of cornea donors and the risk of rejection, the researchers began to explore alternative solutions, including artificial corneas.
What Is Cornea Transplantation?
Corneal transplantation is a surgical procedure also called keratoplasty. This procedure involves replacing a damaged, injured, or diseased cornea with a healthy donor cornea. This procedure can restore clear vision, improve the appearance of diseased or damaged corneas, and reduce pain in individuals with conditions such as corneal scarring, corneal endothelial dysfunction, or keratoconus. Usually, corneal transplants use human donor corneas obtained from deceased individuals. This approach has been successful for many affected individuals. However, it has many limitations and side effects.
What Is Artificial Cornea?
Artificial corona, also called keratoprosthesis, is a device used for corneal transplantation procedures. This surgical procedure replaces a diseased cornea with an artificial cornea. The concept of the artificial cornea was first proposed by Guillaume Pellier de Quengsy, a French ophthalmologist, in 1789. Usually, keratoprosthesis is recommended after a person has had one or more corneal transplant rejections or has certain conditions for which various types of corneal transplantation will not be effective.
Such conditions include ocular surface diseases like congenital aniridia, severe dry eyes, Stevens-Johnson’s syndrome, limbal stem cell deficiency, or chemical burns. In such conditions, artificial cornea transplantation may be recommended. Keratoprosthesis comprises clear plastic with excellent optical properties and tissue tolerance ability. The artificial corona may vary in size, and design, and even the surgical techniques may differ across various treatment centers. This surgical procedure is usually performed by an ophthalmologist, often outpatient.
What Are the Types of Artificial Cornea?
Artificial corneas come in various types, each with its own unique design, size, and material.
Only a few models are currently in commercial use, which include:
1) Osteo-Odonto-Keratoprosthesis (OOKP) - It is used to manage severe ocular surface disorders. This procedure is implicated in various complex surgical procedures. This method is also referred to as “tooth-in-eye" surgery. This procedure removes a tooth from the patient or a donor. A hole is drilled perpendicular to the longitudinal lamina after it is cut from the tooth. The hole is then attached to a cylindrical lens. The created lamina is grown in the cheek of the patient for a few months and then implanted in the patient's eye. This procedure is indicated in severe pemphigoid, Lyell syndrome, Stevens–Johnson syndrome, trachoma, chemical burns, and multiple corneal graft failures.
2) Boston Keratoprosthesis - The Boston keratoprosthesis is the most commonly used artificial cornea. It is made up of a material that does not opacify. It has two parts with a collar button, and the front plate has a stem, which includes the optical portion of the device. The back plate has a titanium locking c-ring. It is available in two types: type I and type II formats. Type 1 is used in patients with normal blinking and enough tear secretion. Type 2 is used for patients with ocular surface disease and severe dryness. The Boston keratoprosthesis is indicated for corneal disorders unsuitable for standard corneal transplantation. It is the primary treatment option for patients with one or more corneal graft rejections, aniridia, herpetic keratitis, and many congenital corneal opacities.
3) AlphaCor - It is made up of poly-2-hydroxyethyl methacrylate (pHEMA). It is used in cases of several graft failures or keratoplasty risk cases. This device contains a transparent central region and a peripheral skirt. The cornea measures 0.5 mm (millimeters) in thickness and 7.0 mm in diameter. The main advantage of this device is an interpenetrating polymer network formed between the two parts. This network prevents complications that arise at their interface.
4) KeraKlear - KeraKlear is made up of a strong biocompatible material which is clear and flexible. It is 7.0 mm in diameter. This is implanted into a partial-thickness corneal pocket made by a femtosecond laser with a 3.5 mm diameter opening. This is indicated for patients with non-inflammatory corneal blindness, such as corneal dystrophies, corneal scars, keratoconus, and corneal edema. The KeraKlear is contraindicated in patients with inflammatory causes of corneal blindness, such as ocular cicatricial pemphigoid, Stevens johnson syndrome, or atopic keratoconjunctivitis.
What Are the Advantages of Artificial Cornea?
Artificial corneas have several potential benefits when compared to traditional corneal transplantation:
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Increased Availability - In the case of traditional cornea transplantation, the availability of a donor is not always possible. However, the artificial corneas are produced mechanically, ensuring a consistent supply for needy patients. This reduces the shortage of donor corneas and the waiting period for donors.
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Reduced Rejection Risks - Artificial corneas are made from biocompatible materials; the rejection risk is significantly lower than that of traditional corneal transplantation.
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Customization - Artificial corneas can be custom-made to individual patient requirements based on shape, size, and optical properties, which allows for better outcomes and great visual clarity after transplantation.
What Are the Risks of Artificial Cornea?
The success rate with keratoprosthesis is generally high. However, in certain rare cases, serious complications can occur.
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Extrusion of the implant.
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Sudden occurrence of creamy white, cottonlike, well-circumscribed lesions involving the retina and choroid and extending into the vitreous cavity can cause a drastic reduction in vision.
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Inflammation of the eye tissue.
Conclusion
Artificial corneas are a promising alternative to traditional corneal transplantation. Compared to traditional corneal transplantation, artificial cornea offers reduced risk of rejection, increased availability, and improved customization. However, challenges such as certain eye disorders, inflammation, and affordability will make it important to check for the full potential of artificial corneas in clinical practice. With ongoing advancements in medical science and surgical techniques, these innovative technologies will benefit the evolution of the field of corneal transplantation.
