Clinical study of laminar resorption: Part 1 – Factors affecting laminar resorption
Introduction
Osteo-odonto-keratoprosthesis (OOKP) is a unique device among the keratoprostheses (KPros) in having a biological haptic and a synthetic polymeric optic. Its success is hard earned and multiple factors such as case selection, surgeon's experience, the surgical technique used, and most importantly post-operative care and timely intervention are crucial to the success and longevity of the device. Hence, OOKP is only offered to one eye at a time and should be the last resort attempt for visual rehabilitation of eyes with end-stage ocular surface disease (OSD).
Understanding the anatomical and functional changes of the eye after OOKP surgery is essential for the comprehension of clinical signs of resorption. After implantation of the OOKP device, the structure of the anterior segment changes significantly. OOKP involves a multi-stage procedure, the details of the OOKP surgical technique were given in our previous publication [1]. The skirt is made from an alveo-dental tissue composite, the osteo-dento-acrylic lamina (ODAL), which is prepared from the root of a tooth along with its adjoining bone fragment (Fig. 1 top left). In this procedure, the ocular surface is layered with a thick patch of buccal mucosa. During the stage 1 operation of OOKP, the buccal mucosa is grafted over the surface of the eye, and the lamina is prepared and inserted into the contralateral sub-orbicularis pouch for connective tissue ingrowth (Fig. 1 top right). Mucosal maturation and vascular investment of the lamina generally requires a waiting period of 2–4 months. The lamina is attached to the surface of the cornea under the mucosa, but the long optical stem traverses through the mucosa, lamina and anterior chamber. The distal end of the cylinder projects outwards beyond the mucosal surface (Fig. 1 bottom left). The acrylic optical cylinder has a broader end, which projects through the alveolar surface, and a narrower end which is inserted into the anterior chamber (Fig. 1 bottom right). The dentinal surface of the lamina is directly opposed to the cornea and sclera, and the alveolar surface has a connective tissue covering through which it connects to the inner side of the buccal mucosa (Fig. 1 bottom right). In patients without suitable teeth, laminae can be constructed from tooth allografts from living related or unrelated donors, and autologous tibial cortical fragments (osteo-keratoprosthesis or OKP).
A variety of complications can occur after OOKP such as those related to the mucosa, eyelids, glaucoma and retina. A specific complication of the lamina is resorption, which can reduce the life span of the lamina. This can lead to serious sight-threatening complications such as endophthalmitis, loss of vision, loss of lamina and even eye. Therefore, the OOKP surgeons should be constantly vigilant about the development of resorption. Its incidence has been variably reported in the literature without a definitive clinical description [2]. Tan and colleagues identified that lamina survival is reported between 0 and 43% in published studies [3]. In this paper (part-1) we presented the factors affecting laminar resorption and in the subsequent paper (part-2) we report on the detection and outcomes of laminar resorption.
Section snippets
Methods
This study was conducted at the Sussex Eye Hospital in Brighton, UK, from the cohort of patients who underwent OOKP and OKP between 1996 and 2014. This study was approved by the institutional research department. A retrospective review of case records and prospective assessment and documentation of the findings from the patients under follow-up was conducted. Patient data was collected on Microsoft Excel and Word (Microsoft, Redmond, WA, USA). The data was analysed and statistical tests were
Results
When reporting the findings of resorption, as a standard each lamina was treated as an independent case. The tibial laminae showed effects of resorption similar to the allografts, and some patients received both allo and tibial laminae in succession; hence, these two laminae were studied as one group to avoid confounding factors. In this study, 64 patients (25 females and 39 males) were included and in total 74 laminae were employed, which consisted of 3 tibial grafts, 11 tooth allografts and
Discussion
The success of the OOKP is due to excellent biocompatibility, integration and durability of the lamina, which is protected and nourished by a sturdy biological membranous cover made of the buccal mucosa. The lamina is a composite of two layers: dentine and alveolus, which are conjoined by a connective tissue layer called alveo-dental ligament. The alveolar segment is derived from the connecting wall of the tooth socket, called alveolus, with the root of the tooth. The alveo-dental or
Declaration of competing interest
None.
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