A Tooth for an Eye Even if earplugs work, it is still important to know what snoring really means By Prof Donald Tan and Dr Julian Theng The newest buzzword in ophthalmology for the latest in advanced, complex sight-saving eye surgery for the worst cases of severe corneal blindness is osteo-odonto keratoprosthesis (OOKP). This procedure effectively replaces the entire front half of the eye with a tooth-optical cylinder device made from the patient’s own canine tooth and jawbone, in which an artificial plastic cornea is implanted. This device is implanted with a large mucosal transplant from the patient’s inner cheek lining. OOKP surgery salvages vision in eyes with damage so severe that conventional corneal transplant or stem cell transplants do not help.    Who benefits from OOKP? This procedure may assist patients who have been blind in both eyes from end-stage corneal diseases such as::      •   Previous failed corneal and ocular surface transplants with severe dry eye states:      •   Cicatricial ocular surface disorders, namely Stevens Johnson syndrome; severe chemical          burns; ocular cicatricial pemphigoid (OCP)      •   Trachoma   In the past, according to Professor Donald Tan, senior eye surgeon at Singapore National Eye Centre (SNEC), patients with severe chemical and thermal burns, or Stevens Johnson syndrome were considered “failures of treatment”. Some even ended up in blind registries. With the promise of vision restoration from OOKP, it is hoped that doctors will revisit and treat these patients. However, OOKP has its limitations. Patients who have optic nerve or retinal diseases of the eye such as glaucoma and age-related macular degeneration will not benefit from treatment.   The development of OOKP in Singapore The OOKP programme is a project of two institutions under the SingHealth group: The Singapore National Eye Centre (SNEC) and National Dental Centre (NDC). Prof Tan (principal Investigator), Dr Julian Theng (coinvestigator), Dr Andrew Tay (senior oral surgeon), and Dr Eric Lye Kok Weng (oral surgeon) lead a large team of surgeons. Dr Christopher Liu from Brighton, UK, SNEC’s visiting senior consultant, is the programme advisor.   In February 2004, 19-year-old Luck Pewnual from Thailand, who had been blind in both eyes for six years from severe Stevens Johnson syndrome, was the first to receive OOKP surgery.   To date, the SNEC/NDC team has performed OOKP on 14 patients from Singapore, Thailand, Malaysia, Indonesia, Sri Lanka and Bangladesh, all with severe bilateral end-stage corneal diseases. Twelve have undergone stage 2 procedures. The outcomes have been excellent thus far: almost 5 of 12 now have perfect vision, nine have driving vision, while the rest have reached their best visual potential – vision is limited in these patients due to pre-existing glaucoma or retinal pathology. What is even more impressive with this procedure is that there have been no major complications relating to keratoprosthesis, despite the mean follow-up currently exceeding one year.   The longest follow-up to date is 20 months: Prior to surgery, Luck Pewnual could see only hand movements in either eye. He now sees 6/6 in his right operated eye with spectacles, and has returned to school and a normal lifestyle.   In 2005, the SNEC/NDC team won first prize for innovative new surgical procedures at the annual meeting of the American Society of Cataract and Refractive Surgery. The video documenting Pewnual’s surgery has since been incorporated into two new books on eye surgery. The OOKP program has also received intense publicity locally and overseas – particularly in India, Indonesia, Malaysia, China, Thailand and Sri Lanka.   “We will continue to perform OOKP surgery in more patients in need of vision restoration and will continue longer follow-up to ascertain the long-term survival of these biological implants in the eye, and to see if visual rehabilitation in these patients is sustained,” says Prof Tan.   Prof Donald Tan is a senior eye surgeon at the Singapore National Eye Centre (SNEC) and Dr Julian Theng is an eye consultant at the SNEC.     How is the OOKP surgery performed?   OOKP consists of two complex surgical procedures, which are performed 2 to 4 months apart.    Stage 1 of the surgery involves surgical teams from both SNEC and the NDC:      1.   Removing a canine tooth, also know as the “eye tooth,” and part of the adjacent maxillary           bone en bloc      2.   Carefully shaving down the root of the tooth, and drilling a hole through to receive a plastic           OOKP optical cylinder (which has the equivalent optical power of the cornea and lens           combined) which is cemented into place      3.   Implanting the tooth-bone-cylinder complex into the patient’s cheek to grow a new blood           supply      4.   Opening up one eye and removing the entire inner surface of his eyelids, his corneal           surface, and all scar tissue from his previous eye injury over the white portion (sclera) of t           he eye      5.   Removing a large patch of buccal mucosa from the inner cheek and transplanting it onto           the new surface of the eye   Stage 2 is an eight-step procedure:      1.   Reopening of the buccal mucosa in a flap-like fashion to expose the cornea      2.   Trephining a central opening in the cornea      3.   Removal of the entire iris and pupil      4.   Removal of the human crystalline lens      5.   Removal of the anterior vitreous (anterior vitrectomy)      6.   Retrieval of the tooth-bone-cylinder complex from the cheek      7.   Implantation of the tooth-bone-cylinder complex through the corneal opening, securing it in           position with multiple sutures      8.    Replacement of the buccal mucosal flap over the implant and trephining a small hole           centrally over the mucosa to allow the optical cylinder to protrude through, thus allowing           light to enter the eye.