Osteo-Odonto-Keratoprosthesis (OOKP) is a keratoprosthesis conceived by Strampelli in the 1960s. It was later modified by Falcinelli and established as the modified version (MOOKP)2). The fundamental difference from other keratoprostheses is the use of the patient’s own tooth and alveolar bone as a biological haptic.
MOOKP is the ultimate means of visual function recovery for bilateral corneal blindness and end-stage ocular surface disease. It is indicated for severe cases that cannot be managed by conventional corneal transplantation or other keratoprostheses (e.g., Boston KPro).
Following meetings of the OOKP Study Group in Rome in 2001 and Vienna in 2002, the Rome-Vienna protocol was established to standardize and improve the surgical technique2). This is the current gold standard, performed through multidisciplinary collaboration between ophthalmologists and maxillofacial surgeons.
QWhy does MOOKP use a tooth?
A
Because the tooth and alveolar bone are the patient’s own living tissue, the risk of foreign body reaction or rejection is low. Bone tissue is rich in blood vessels and has excellent biocompatibility, making it suitable for long-term support and nutrient supply to the PMMA optical cylinder. Compared to other keratoprostheses made entirely of synthetic materials, the main advantage is stable fixation provided by the biological haptic.
Children are an absolute contraindication because the dental arch is underdeveloped and the risk of lamina resorption is high.
QWhat is the difference between Boston KPro and MOOKP?
A
Boston KPro (type 1) is the most widely used keratoprosthesis, but outcomes are poor in severe ocular surface disorders. MOOKP uses autologous tooth and bone as a biological support, making it effective for end-stage ocular surface diseases such as severe autoimmune diseases or chemical trauma that are difficult to manage with Boston KPro. However, MOOKP surgery is extremely complex and multi-staged, and dental conditions must also be met.
Record the visual acuity of minimal light perception. Assess light perception, light projection, entoptic phenomena, and color discrimination. Use PAM device, laser interferometer, flash electroretinogram (fERG), and visual evoked potential (VEP) to evaluate potential visual acuity.
Glaucoma is the most common cause of vision loss in MOOKP patients. Iyer et al. reported that among 85 eyes of 82 MOOKP cases, elevated intraocular pressure was observed pre- or postoperatively in 22 eyes of 20 cases, indicating that glaucoma management is extremely important 3). Confirming the diagnosis of glaucoma preoperatively is crucial.
The maxillofacial surgeon performs a dental examination. This includes evaluation of the oral mucosa and selection of an appropriate tooth. Usually, a single-rooted tooth such as a canine is selected.
Imaging studies include orthopantomography (panoramic X-ray) and cone-beam CT (CBCT). These are essential for assessing tooth integrity and surgical planning.
Chlorhexidine and nystatin mouth rinses are started 1–2 days before surgery. Smoking cessation is also required.
Underlying diseases such as SJS or TEN may involve lesions on the face, neck, and airway. Evaluation using the Mallampati classification and ASA physical status classification is necessary.
MOOKP is a complex surgery performed in three stages.
Stage 1
Preparation of the anterior and posterior segments: Removal of ocular surface tissue, conjunctival incision, limbal incision, removal of anterior synechiae, iris, and lens, and vitrectomy.
OOAL fabrication: The maxillofacial surgeon osteotomizes a single-rooted tooth along with surrounding alveolar bone and periosteum. After pulp removal, a PMMA optical cylinder is bonded with bone cement.
Subcutaneous implantation: The fabricated OOAL is implanted subcutaneously in the contralateral zygomatic region.
Intermediate stage (1 month later)
Oral mucosal harvesting: Under general anesthesia, a 3–4 cm full-thickness oral mucosal graft is harvested.
Ocular surface reconstruction: The corneal epithelium and Bowman’s layer are removed, and the mucosal graft is sutured onto the ocular surface.
Perforation management: If perforation or Descemetocele is present, corneal transplantation is performed concurrently.
Second stage (3 months later)
OOAL removal: The OOAL is removed from the subcutaneous pocket and examined for absorption or necrosis.
Placement onto the cornea: The mucosal graft is incised to create a flap. The central cornea is trephined, and the posterior surface of the OOAL optical cylinder is fitted and sutured in place.
Mucosal management: After closing the flap, a trephine incision is made to expose the anterior surface of the optical cylinder.
The recommended dimensions for the dental lamina are 15–16 mm in length, 8–10 mm in width, and at least 3 mm in thickness. The optical cylinder is individually designed to achieve emmetropia as closely as possible.
After the intermediate stage, a bactericidal mouthwash (0.2% chlorhexidine) is used. After each stage, systemic and topical broad-spectrum antibiotics and steroids are administered.
After the second stage, intraocular pressure is managed with acetazolamide as needed. A scleral shield is placed, and the patient remains supine until the intracameral air is absorbed. Daily cleaning of the optical cylinder (using BSS) is continued.
In a long-term cohort study of 181 cases (98 males, 83 females, mean age 54.3 years) by Falcinelli et al., anatomical failure occurred in only 11 cases (6.07%), and the OOKP retention probability at 18 years was 85% (95% CI: 79.3-90.7%) 4). The mean best postoperative visual acuity in the same cohort was 0.76, and it was maintained at 0.69 at the final follow-up 4).
A global analysis integrating 958 cases from 37 studies reported the following results 1):
Mean anatomical success rate at final follow-up: 88.25% (range 50-100%)
Achievement of visual acuity of 20/400 (0.05) or better: 78%
At least temporary visual improvement after surgery: 91.2%
A systematic review by Tan et al. also reported a 5-year anatomical survival rate of 87.8% and a 20-year survival rate of 81.0%, surpassing other corneal prostheses in long-term survival 5). Visual outcomes vary by diagnostic group. For bullous keratopathy after glaucoma surgery, it was 0.41 logMAR; for corneal burns and dry eye syndrome, it was 0.8 logMAR.
Intraoperative complications: Exposure of adjacent tooth roots, perforation of the oral mucosal flap, oral numbness or tightness, submucosal scar bands, infection at the graft site, and vitreous hemorrhage may occur. In the systematic review by Tan et al., the most frequent intraoperative complication was vitreous hemorrhage (0-52%) 5).
Postoperative complications
Lamellar resorption: One of the most frequent complications. It directly leads to anatomical failure. CT scan is the gold standard for detection.
Aseptic vitritis: Often associated with early lamellar resorption.
Glaucoma: A significant complication common to all corneal prostheses and the most vision-threatening complication in the long term (incidence 7-47%) 5). Iyer et al. reported that by performing early Ahmed glaucoma valve implantation as stage 1A, intraocular pressure was controlled for an average of 33.68 months in 11 of 15 eyes (73.3%) 3).
Chorioretinal detachment, retroprosthetic membrane, vitreous hemorrhage, endophthalmitis: The incidence of endophthalmitis is reported to be 2-8%5). Lim et al. reported that complications requiring vitreoretinal surgery occur at a certain rate6).
QWhat is the long-term prognosis of MOOKP?
A
With careful patient selection and strict follow-up, MOOKP shows reliable long-term prognosis for end-stage ocular surface disease. Anatomical success rate of 85% is maintained over 18 years of follow-up. However, due to risks of complications such as lamellar resorption and glaucoma, lifelong regular follow-up is essential.
Ortiz-Morales G, Loya-Garcia D, Colorado-Zavala MF, et al. The evolution of the modified osteo-odonto-keratoprosthesis, its reliability, and long-term visual rehabilitation prognosis: An analytical review. Ocul Surf. 2022;24:129-144. PMID: 35314421. doi:10.1016/j.jtos.2022.03.005
Hille K, Grabner G, Liu C, et al. Standards for modified osteoodontokeratoprosthesis (OOKP) surgery according to Strampelli and Falcinelli: the Rome-Vienna Protocol. Cornea. 2005;24(8):895-908. PMID: 16227830. doi:10.1097/01.ico.0000157401.81408.62
Iyer G, Srinivasan B, Agarwal S, et al. Glaucoma in modified osteo-odonto-keratoprosthesis eyes: role of additional stage 1A and Ahmed glaucoma drainage device-technique and timing. Am J Ophthalmol. 2015;159(3):482-489.e2. PMID: 25461297. doi:10.1016/j.ajo.2014.11.030
Falcinelli G, Falsini B, Taloni M, Colliardo P, Falcinelli G. Modified osteo-odonto-keratoprosthesis for treatment of corneal blindness: long-term anatomical and functional outcomes in 181 cases. Arch Ophthalmol. 2005;123(10):1319-1329. PMID: 16219722. doi:10.1001/archopht.123.10.1319
Tan A, Tan DT, Tan XW, Mehta JS. Osteo-odonto keratoprosthesis: systematic review of surgical outcomes and complication rates. Ocul Surf. 2012;10(1):15-25. PMID: 22330056. doi:10.1016/j.jtos.2012.01.003
Lim LS, Ang CL, Wong E, Wong DW, Tan DT. Vitreoretinal complications and vitreoretinal surgery in osteo-odonto-keratoprosthesis surgery. Am J Ophthalmol. 2014;157(2):349-354. PMID: 24332375. doi:10.1016/j.ajo.2013.08.033
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