TOOTH-IN-EYE SURGERY: ALL YOU NEED TO KNOW ABOUT OOKP

Vision is one of the most important senses, and losing it can significantly impact one's quality of life. Fortunately, advances in medical technology have made vision restoration possible with innovative surgeries like Osteo Odonto Keratoprosthesis (OOKP), also known as tooth-in-eye surgery.

The concept of OOKP surgery is more than 200 years old. The first prosthetic made from a tooth was introduced in the 1960s by Professor Strampelli^[1], an Italian ophthalmologist, after many attempts using various materials, including glass, metal, and quartz crystal. However, it was in the 1980s that the surgery gained popularity when Professor Falcinelli, also from Italy, refined the technique and achieved successful results.

Since then, over 4,500 OOKP surgeries have been performed worldwide^[2]. It has become increasingly more popular as an option for patients with severe visual impairment due to end-stage ocular surface disease, where traditional corneal transplants are not feasible or have failed.

This article will explore the history, procedure, potential benefits and risks, recovery, long-term management, and the future of this groundbreaking surgery.

The Need for OOKP

Ocular surface diseases, characterized by symptoms like dryness, redness, and irritation, can profoundly impact daily activities by causing discomfort and hindering visual clarity. These symptoms can make tasks such as reading, driving, and engaging in social activities challenging, emphasizing the need for effective treatments.

Traditional corneal transplants involve replacing the damaged cornea with a donor cornea and have been the standard of treatment for decades. However, this procedure has its limitations.

A 2016 survey also reveals that out of the 4.5 million potential candidates for corneal transplant surgery, there is only one donor cornea per 70 individuals. The survey also shows that 53% of the world's population lacks access to corneal surgery^[3].

Traditional corneal transplantation also poses a high risk of rejection, occurring in three out of every ten people who undergo the procedure^[4]. Other complications include graft detachment, post-operative infection, and degeneration of the donor cornea. Those with surface ocular diseases often lose their corneas due to inflammation and infection, which can re-emerge after a traditional transplant and lead to a second transplant.

In such cases, OOKP surgery offers a viable alternative. OOKP surgery utilizes the patient's tooth and tissue to create a stable and long-lasting artificial cornea that is less susceptible to recurrent corneal infections. This method minimizes reactivity around the area, lowering the risk of graft rejection and detachment.

How Tooth in Eye Surgery Works?

In OOKP surgery, the patient's tooth is extracted and shaped into an artificial cornea to fit into the eye. The surrounding tissue then supports the implant. This procedure eliminates the risk of rejection and supplies a stable, long-lasting solution for patients with severe visual impairment.^[5]

A keratoprosthesis implant is a complex structure made up of several parts. The main body of the implant is a tooth root, usually a canine tooth, attached to a segment of bone tissue that undergoes shaping to accommodate a biocompatible acrylic cylinder. The tooth root provides structural support for the cylinder, which acts as the artificial cornea or eye lens and allows light to pass through to the retina. The implant also includes a skirt made of bone tissue, which helps to hold the implant in place and prevent infection.

The OOKP implant improves vision by replacing the damaged cornea with a clear artificial cornea. When light passes through the artificial cornea to the retina, it converts to electrical signals sent to the brain. This process can enable people with corneal blindness to see again.

The OOKP Surgery Procedure

OOKP surgery is a complex and delicate procedure that requires a highly skilled team. There are typically two stages to the surgery, with a 3-6 months gap between them.

Before Osteo Odonto Keratoprosthesis (OOKP) surgery, a surgeon thoroughly evaluates the patient's ocular condition and dental health. This assessment includes weighing the severity of the ocular surface disease and determining the suitability of the tooth for the procedure.

Additionally, imaging techniques and dental assessments help to gather essential information for the surgery.

Stage 1: Dental Phase

The chosen tooth, typically a canine or premolar, and the surrounding tissue are carefully extracted in this phase.

The extracted tooth is then shaped and prepared as the artificial cornea. This preparation involves removing the dental pulp and reshaping the tooth to resemble a dome-like structure.

Stage 2: Ocular Phase

The ocular phase begins with the preparation of the eye for implantation. The surgeon removes the damaged cornea by creating a round incision called a trephination opening.

The prepared tooth is then implanted into the eye and secured. Tissue grafting and suturing ensure proper integration and stability of the implant within the eye.

Potential Benefits and Risks

The potential benefits of OOKP surgery include improved vision, reduced risk of rejection, and a long-lasting solution for severe visual impairment. The success rate for the surgery is very high, standing at 93.9%^[6].

One patient regained their eyesight after 21 years of corneal blindness^[7]. After the surgery, it took several weeks for her to regain full sight, with light returning first, followed by blurred vision to complete sight restoration. This case highlights the type of patient that benefits the most from this surgery, where traditional corneal transplantation will not suffice.

However, like any surgery, there are also potential risks involved.

One of the main risks of OOKP surgery is the possibility of losing the implant. Implant loss can happen due to infection and inflammation. Other complications may include implant infection, glaucoma, and problems with the dental portion of the OOKP.

Strategies to minimize the risks include meticulous surgical technique, proper patient selection, and adherence to postoperative care instructions. Prompt identification and management of complications contribute to successful outcomes.

Recovery and Long-Term Management

The recovery period for OOKP surgery can vary from patient to patient, yet it typically takes around 6-8 weeks after the second phase and 3-6 months after the first phase. The combined time makes the total duration of surgery recovery approximately 4.5-8 months.

Patients must postpone engaging in strenuous activity until after recovery and follow their surgeon’s post-operative care instructions.

Long-term management and care are crucial for the success of OOKP surgery. Patients must attend routine follow-up meetings with their surgeon to monitor the implant's health and ensure it functions correctly.

In addition, patients must maintain good oral hygiene to prevent any complications with the tooth used for the artificial cornea. They may also need eye drops or other medications to prevent infection and inflammation.

Who is a Good Candidate for OOKP Surgery?

OOKP surgery usually treats corneal blindness in one or both eyes. A specialist commonly recommends it for those with severe visual impairment that arises from end-stage ocular surface diseases, such as:

• Stevens-Johnson Syndrome
• Ocular cicatricial pemphigoid
• Trachoma
• Lyell syndrome
• Epidermolysis bullosa acquisita
• Severe keratitis, xerosis, or uveitis

It may also be suitable for patients who have eye trauma, have multiple failed corneal transplants, or have other conditions that make traditional corneal transplants challenging.

However, not everyone is a good candidate for OOKP surgery.

Specific medical ailments, including uncontrolled diabetes or autoimmune diseases, may disqualify some patients from surgery. Other contraindications include:

• Eyes incapable of perceiving light or phthisis (surgery would only inflict further damage)
• Severe glaucoma
• Irreparable retinal detachment
• Those with habits like smoking, chewing betel nuts, or with poor dental health
• Kids below 17 years old (due to the high bone turnover rate associated with this growth stage)
• Mentally challenged patients
• Those unable to follow up on their implant's condition routinely

It is essential to consult with an experienced ophthalmologist to determine if OOKP surgery is the right option for you.

Recent Advances and Future of OOKP Surgery

OOKP surgery has come a long way since its inception. Technological advancements and technique refinements continue to improve its success rates. A few noteworthy mentions include^[8]:

• The optical cylinder in an OOKP implant has been improved for better vision and less glare. Surgeons now better manage complications like buccal mucosal ulceration and glaucoma, leading to higher success rates for the implant.
• The Boston Keratoprosthesis (KPro) switched from using Poly methyl methacrylate to a titanium backplate to reduce complications. The newer models make implantation more straightforward and are more affordable.
• Eye pressure and glaucoma risks are lower due to an inbuilt intraocular pressure sensor and easier access to shunt tube surgery to alleviate eye pressure.
• The design of the artificial lens is more accommodating of the eye, protruding outwards instead of contributing towards internal pressure.
• Improved postoperative care, including antibiotics and bandage contact lenses, reduces infection risks.

The future of OOKP surgery looks bright, with ongoing research and development to improve the procedure and make it more accessible to patients worldwide.

With the increasing prevalence of corneal blindness, OOKP surgery can potentially restore vision for many individuals and improve their quality of life.

Conclusion

OOKP surgery, also known as tooth-in-eye surgery, is a groundbreaking procedure that has helped restore vision for many individuals worldwide. With its high success rate and long-term benefits, it offers a viable alternative to traditional corneal transplants for patients with severe visual impairment occurring from advanced ocular surface disease.

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