J Herold

The osteo-odonto-keratoprosthesis (OOKP).

The osteo-odonto-keratoprosthesis (OOKP), although described over 40 years ago, remains the keratoprosthesis of choice for end-stage corneal blindness not amenable to penetrating keratoplasty. It is particularly resilient to a hostile environment such as the dry keratinized eye resulting from severe Stevens-Johnson syndrome, ocular cicatricial pemphigoid, trachoma, and chemical injury. Its rigid optical cylinder gives excellent image resolution and quality. The desirable properties of the theoretical ideal keratoprosthesis is described. The indications, contraindications, and patient assessment (eye, tooth, buccal mucosa, psychology) for OOKP surgery are described. The surgical and anaesthetic techniques are described. Follow-up is life-long in order to detect and treat complications, which include oral, oculoplastic, glaucoma, vitreo-retinal complications and extrusion of the device. Resorption of the osteo-odonto-lamina is responsible for extrusion, and this is more pronounced in tooth allografts. Regular imaging with spiral-CT or electron beam tomography can help detect bone and dentine loss. The optical cylinder design is discussed. Preliminary work towards the development of a synthetic OOKP analogue is described. Finally, we describe how to set up an OOKP national referral center.

Visual rehabilitation in end-stage inflammatory ocular surface disease with the osteo-odonto-keratoprosthesis: results from the UK

Aims: To report the long-term results of osteo-odonto-keratoprosthesis (OOKP) surgery in the visual rehabilitation of patients with corneal blindness from end-stage inflammatory ocular surface disease. Methods: A non-comparative retrospective case series of 36 consecutive patients treated at the National OOKP referral centre in Brighton, UK, between November 1996 and March 2006. Results: A total of 36 patients, with age ranging from 19 to 87 years (mean 51 (SD 19) years), were included in the analysis. The main preoperative diagnoses were Stevens–Johnson syndrome (n = 16, or 44%), severe thermal or chemical burns (n = 6, or 17%), and mucous membrane pemphigoid (n = 5, or 14%). The remainder of the cases comprised miscellaneous causes of dry eye (n = 9, or 25%), which included one each of graft versus host disease, ectodermal dysplasia, ionising radiation damage, cicatrising conjunctivitis from topical medication, trachoma, congenital trigeminal nerve hypoplasia, linear IgA disease, Sjögren syndrome and nutritional deficiency. Follow-up ranged from 6 months to 9 years (mean 3.9 (SD 2.5) years). Anatomical retention during the entirety of the follow-up period was seen in 72% of patients. The main factor resulting in anatomical failure was resorption of the OOKP lamina, which occurred in seven cases (or 19%). Predicted resorption in three cases resulted in successful planned exchange of the lamina, but two cases underwent emergency removal of the OOKP, and two cases developed endophthalmitis. Human leucocyte antigen-matched allografts suffered a higher rate of laminar resorption. Out of the entire cohort, 30 patients (or 83%) had some improvement in vision, 28 (or 78%) achieved vision of 6/60 or better, and 19 (or 53%) achieved 6/12 or better. The best-achieved vision was retained throughout the follow-up period in 61% of cases. Survival analysis suggested that the probability of retaining vision >6/60 5 years after surgery was 53 (10)%. Vision-threatening complications occurred in nine cases (or 25%) and included endophthalmitis, retinal detachment and glaucoma. De novo glaucoma occurred in six patients (or 24%) but was seen overall in 17 patients (or 47%), 10 of whom required surgical treatment. Conclusion: OOKP surgery can restore useful and lasting vision in patients suffering from end-stage ocular surface disease, for whom conventional corneal surgery is not possible. The main problems seen in this study were laminar resorption, particularly in allografts, and glaucoma.

Vitreoretinal complications of osteoodontokeratoprosthesis surgery.

Purpose: To describe the vitreoretinal complications in a cohort of patients with osteoodontokeratoprosthesis (OOKP) and discuss surgical management. Methods: Review of notes of 35 OOKP cases performed at the Sussex Eye Hospital (Brighton, United Kingdom) between January 1999 and December 2005 was performed. Results: The overall incidence of vitreoretinal complications was 22.8%, which included vitreous hemorrhage (3 patients), rhegmatogenous retinal detachment (3 patients), endophthalmitis with retinal detachment complicating lamina resorption and optic extrusion (2 patients), and intraoperative choroidal hemorrhage (1 patient). Preexisting aphakia was associated with rhegmatogenous retinal detachment (P < 0.05, &khgr;2 = 4.36). Five patients required pars plana vitrectomy, which was performed either endoscopically (two cases) or using a binocular indirect viewing system (three cases) with one case requiring removal of the OOKP and insertion of a temporary keratoprosthesis. Retinal detachment repair was attempted on four of five patients but was successful for only one. Vitreous hemorrhage without retinal detachment required vitrectomy in one case, while two cases cleared spontaneously. Conclusions: Eyes receiving OOKP are prone to vitreoretinal complications, with retinal detachment associated with a poor prognosis. Thicker OOKP laminae and lamina bulk screening will hopefully reduce the risk of endophthalmitis due to unexpected resorption.

Serial 3-dimensional computed tomography and a novel method of volumetric analysis for the evaluation of the osteo-odonto-keratoprosthesis.

Purpose: To assess the use of serial computed tomography (CT) in the detection of osteo-odonto-lamina resorption in osteo-odonto-keratoprosthesis (OOKP) and to investigate the use of new volumetric software, Advanced Lung Analysis software (3D-ALA; GE Healthcare), for detecting changes in OOKP laminar volume. Methods: A retrospective assessment of the radiological databases and hospital records was performed for 22 OOKP patients treated at the National OOKP referral center in Brighton, United Kingdom. Three-dimensional surface reconstructions of the OOKP laminae were performed using stored CT data. For the 2-dimensional linear analysis, the linear dimensions of the reconstructed laminae were measured, compared with original measurements taken at the time of surgery, and then assigned a CT grade based on a predetermined resorption grading scale. The volumetric analysis involved calculating the laminar volumes using 3D-ALA. The effectiveness of 2-dimensional linear analysis, volumetric analysis, and clinical examination in detecting laminar resorption was compared. Results: The mean change in laminar volume between the first and second scans was −6.67% (range, +10.13% to −24.86%). CT grades assigned to patients based on laminar dimension measurements remained the same, despite significant changes in laminar volumes. Clinical examination failed to identify 60% of patients who were found to have resorption on volumetric analysis. Conclusions: Currently, the detection of laminar resorption relies on clinical examination and the measurement of laminar dimensions on the 2- and 3-dimensional radiological images. Laminar volume measurement is a useful new addition to the armamentarium. It provides an objective tool that allows for a precise and reproducible assessment of laminar resorption.

Imaging of osteo-odonto-keratoprosthesis by electron beam tomography

Aim: To describe the experience of using electron beam tomography (EBT) in imaging of osteo-odonto-keratoprosthesis (OOKP) to identify early bone and dentine loss which may threaten the viability of the eye. Methods: Seven patients with an OOKP in one eye underwent EBT. The OOKP lamina dimensions were measured on EBT and compared to the manual measurements at the time of surgery. Results: There was a high degree of resolution of the OOKP lamina noted with EBT. In particular, it identified three patients with a marked degree of thinning of the lamina edges. Two of these patients had OOKP that were allografts. The mean time from surgery to examination was 3.6 years (range 1.2–5 years) while the mean age of the patients was 56 years (range 31–79 years). Conclusions: It is important to monitor regularly the dimensions and stability of the OOKP lamina as it will help detect cases that are at risk of extrusion of the optical cylinder and consequent endophthalmitis. Prophylactic measures can then be taken to prevent such serious complications from occurring. In this series, the authors found EBT to have excellent resolution and speed and they would support regular scanning of the OOKP lamina in all patients.

Blindness due to the IgA variant of epidermolysis bullosa acquisita, and treatment with osteo-odonto-keratoprosthesis.

neoplasm, our patient as well as several previously reported cases clearly demonstrate that in patients with autoimmune blistering diseases such figurate erythema may occur in the absence of neoplasia. Irrespective of its clinical manifestation, EBA is associated with autoantibodies to type VII collagen. Patients’ autoantibodies belonging to different IgG subclasses mainly target epitopes within the NC1 domain of type VII collagen. IgG autoantibodies to type VII collagen mainly belong to the IgG1 and IgG4 and to the IgG3 subclasses in EBA and IBD, respectively. Consistent with these findings, our patient presented IgG1, IgG3 and IgG4 autoantibodies to type VII collagen. While the blister-inducing potential of autoantibodies to type VII collagen is established, their contribution to the pathogenesis of IBD and EGR-like lesions is still unclear. IBD occur in approximately 30% of patients with EBA. Thus EBA is mainly associated with Crohn’s disease, but rarely with UC. The causes and pathomechanisms underlying the association of EBA with IBD are poorly understood. The detection of type VII collagen expression in the colonic mucosa led to the hypothesis that, in the context of chronic inflammation and damage to the overlying mucosa, antigenic epitopes of the type VII collagen molecule are exposed. These newly exposed antigenic epitopes may invoke production of autoantibodies, which, in some patients, also cross-react with type VII collagen and trigger blister formation in the skin. Why EBA associates more often with Crohn’s disease compared with UC is even less clear. When IBD and EBA are associated, the onset of IBD usually precedes by several years the first manifestations of the blistering disease. Interestingly, in our patient, the onset of EBA clearly predated the manifestations of UC. In conclusion, we report that an EGR-like eruption may occur in EBA associated with UC. Our results emphasize the notion that EBA is clinically a heterogeneous disease and suggest EGR to be one of its possible manifestations. Therefore, the differential diagnosis in patients with EGR-like eruptions should also include EBA and other autoimmune blistering skin diseases.

Mitomycin-C for mucous membrane overgrowth in OOKP eyes.

Purpose: The aim of this study was to report the use of mitomycin-C (MMC) in the treatment of mucous membrane overgrowth in eyes with osteo-odonto-keratoprosthesis (OOKP). Methods: Records of 4 cases with mucous membrane overgrowth after stage 2 OOKP surgery were reviewed. Results: All the patients had undergone a mucous membrane trimming procedure followed by MMC application. None of the patients had any episode of recurrence of the mucous membrane overgrowth after a single application of MMC in the follow-up period that ranged from 1 to 11 years. Conclusions: MMC can successfully arrest mucous membrane overgrowth in OOKP-implanted eyes including refractory cases.

Unusual variant of chorda tympani syndrome, its management, and a proposal on the nervous pathways involved

Chorda tympani syndrome is an uncommon condition with similarities to Frey syndrome. We describe a variant of chorda tympani syndrome and its management, and put forward a hypothesis for the nervous pathways involved; something that seems to be lacking in published material.

A study of the real life performance of OOKP optical cylinders

Purpose To evaluate the optical and visual functional characteristics of the Osteo‐Odonto‐Keratoprosthesis (OOKP)

Advances in imaging of the OOKP lamina

Purpose The anatomical integrity of an eye bearing an OOKP depends on the integrity and dimensions of the OOKP lamina itself. The lamina is anchored onto the corneo‐scleral envelope initially through suturing. Later on, the overlying buccal mucous membrane graft adheres onto the soft tissues invested into the bone of the lamina, retaining it and providing a seal to guard against entry of microbes into the eye. The integrity and dimensions of the lamina is ascertained clinically at each hospital visit, and this is aided by periodic radiological imaging.