Evaluation of bone reduction in osteo-odontokeratoprosthesis (OOKP) by three-dimensional computed tomography

Purpose. To study the stability and preservation of the osteodental lamina in osteo-odontokeratoprosthesis (OOKP) according to Strampelli with spiral computed tomography (CT). Methods. Computed tomography of the orbit was performed in nine patients after successful OOKP surgery. Indications for surgery included ocular pemphigoid (three patients), Lyell's syndrome (two patients), graft versus host disease (one patient), and severe chemical bums (three patients). In four eyes, the osteodental lamina was covered with a buccal mucosa graft; in five eyes, a "transpalpebral" approach with the placement of the optical cylinder through the patient's own lid skin was used. The mean time from surgery to examination was 4 years. The age of the patients ranged from 32 to 75 years (mean, 52). Spiral CT in the transaxial plane was performed, followed by three-dimensional (3D) surface reconstruction of the OOKP. The dimensions of the osteodental lamina were measured and compared with measurements taken at the time of surgery. Results. A minor reduction of the lamina, mainly in the anterior and inferior part, could be found in all the patients without loss of stability and integrity of the lamina cylinder complex in seven patients. One patient showed complete resorption of the inferior half of the osteodental lamina, and another patient demonstrated "moth-eaten" dissolution of dentine and bone tissue. No correlation between the degree of reduction in the dimensions and patient age, diagnosis, or length of follow-up could be found. Conclusion. Osteo-odontokeratoprosthesis shows good results in patients with corneal blindness not amenable to keratoplasty. Nevertheless, the surgeon must be aware of eventual signs of dissolution of the osteodental lamina, making close follow-up mandatory. Because ultrasound biomicroscopy cannot be used in these cases, spiral CT with 3D reconstruction seems to be a good diagnostic alternative.