The evolution of the modified osteo-odonto-keratoprosthesis, its reliability, and long-term visual rehabilitation prognosis: An analytical review
Introduction
The modified osteo-odonto-keratoprosthesis (MOOKP) is an epicorneal prosthesis with a polymethyl methacrylate (PMMA) optical cylinder supported with a biological haptic applied to patients with bilateral end-stage ocular surface disease, including Stevens-Johnson Syndrome (SJS), ocular mucous membrane pemphigoid (OMMP), and chemical injury. First designed by Strampelli [1] and later modified by Falcinelli [2], the MOOKP procedure is a heterotrophic autograft that replaces the ocular surface with a full-thickness oral mucosa graft. The latter provides vascular, physical, and microbiological sustenance to the patient's tooth and alveolar bone [2,3].
MOOKP is a complex procedure that demands technical finesse and a multidisciplinary team approach. Although an array of complications may accompany the MOOKP procedure, it has demonstrated the best long-term anatomic and functional success rates compared to all other currently available keratoprostheses (Kpros) in patients with the severe or end-stage ocular surface disease [[2], [3], [4], [5], [6], [7], [8], [9], [10], [11], [12], [13], [14], [15], [16], [17], [18], [19], [20]]. Furthermore using an autograft allows better bio-integration and survival in the setting of severe sicca syndrome [5,21].
In 2001–2002, the surgeons who actively performed the MOOKP adaptation met in Rome and Vienna to discuss the surgical technique in detail and reached a consensus known as the Rome-Vienna protocol [2], and it has become the gold standard for this procedure. Today, only 14 highly specialized centers in four continents around the world offer this procedure [22].
This review aims to analyze and compare the demographic profile, surgical indications, complications, long-term functional and anatomic outcomes for all case series, case reports, and the authors' experience (VP and GI) with the MOOKP procedure.
Section snippets
Biological versus biocompatible keratoprostheses
An ideal corneal prosthesis should provide all the advantages of a corneal allograft but none of its disadvantages. Such desired features include improved optical quality, diminished optical aberrations, specifiable refractive power, bio integration and biocompatibility, resistance against infections, durability, successful drug penetration, patient affordability, and the ease to monitor intraocular pressure [[23], [24], [25], [26]].
Indications and contraindications for MOOKP
Indications for the MOOKP procedure include adult patients with bilateral corneal blindness, end-stage ocular surface disease, and severe limbal stem cell deficiency that cannot be treated within the reasonable expectation of success by any other regenerative or reconstructive method [2]. The more frequent entities treated with MOOKP are SJS, toxic epidermal necrolysis (TEN), OMMP, cicatricial trachoma, ocular surface burns, severe exposure keratopathy, and end-stage autoimmune dry eye (Fig. 1
Preoperative assessment
A multidisciplinary approach and an extensive ophthalmological and dental examination are required for adequate patient selection. An imperative requirement is the patient's commitment to a lifelong follow-up [10]. Ophthalmological assessment should include a full history and examination, emphasizing the evaluation of the retina and optic nerve function. The visual function can be assessed through the light perception and projection test, entoptic phenomena, color discrimination, and macular
Surgical technique [22,54]
Following the Rome-Vienna protocol [2], MOOKP is performed in two stages, ten to sixteen weeks apart. Recent modifications by Iyer et al. to the technique included a preliminary stage, termed Stage 1A [22,46], which is performed one month before the first stage to make the second stage safer and less time-consuming (Table 5). In addition, it allows direct intraoperative visualization of the fundus to estimate visual potential. In certain instances, with a doubtful optic nerve or retinal status,
Data analysis from MOOKP procedures
Retrieval of all published case series of MOOKP was performed in the National Library of Medicine's PubMed, SCOPUS, and Google Scholar databases. Search terms included “osteo-odonto-keratoprosthesis (OOKP)” and “modified osteo-odonto-keratoprosthesis (MOOKP).” No date or language restriction was applied. The last search on the databases was performed in January 2022. Fig. 6 summarizes the search strategy and the results. Thirty-six case series, complication reports, and case reports in English
Future directions and conclusion
Close to five million patients are estimated to have bilateral corneal blindness worldwide, and most of them are from underdeveloped countries [105]. In the US, keratoprosthesis development and adaptation have considerably increased in the past three decades. Nonetheless, KPro implantation has remained a reasonably uncommon procedure, accounting for only 0.6% of yearly corneal transplant surgeries since 2009 [106]. In our search for the literature, we could only find one institution in the US
Methods of literature search
An extensive literature search was performed in the National Library of Medicine's Pubmed, Scopus, Web of Science, and Google Scholar databases for all articles published until January 2022 in any language. The following search terms were used: keratoprosthesis, osteo-odonto-keratoprosthesis, and modified osteo-odonto-keratoprosthesis. Case reports, case series, letters to the editor, review articles, and original articles were included.
Funding
No funding or grant was received for the development of this article.
Declaration of competing interest
None of the authors hold proprietary or commercial interest in any concept or product discussed in this article.
Acknowledgments
None.
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