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J. C. Talajic, F. Costescu, S. Gagne, M. Harissi-Dagher; The Prevalence and Impact of Glaucoma on Visual Rehabilitation Following Boston Keratoprosthesis Type 1 Surgery. Invest. Ophthalmol. Vis. Sci. 2010;51(13):1149.
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The Boston Keratoprosthesis Type 1 (KPro) is an increasingly accepted treatment for corneal blindness. However, in this subset of patients with severe anterior segment disease, glaucoma, an irreversible optic neuropathy, may compromise visual rehabilitation despite successful surgical outcome.This study aims to 1) determine the prevalence of glaucoma and 2) evaluate the impact of glaucoma on visual rehabilitation post KPro.
A review was conducted on 39 patients having undergone KPro surgery since October 2008. Pre-operative assessment, operative protocol, and progress notes were reviewed regarding ophthalmic diagnosis, pre- and post-operative visual acuity (VA), intraocular pressure (IOP), visual fields (VF), optic disc examination, and glaucoma-related complications. The impact of glaucomatous damage on visual potential, the progression of glaucoma and the need for its medical and surgical treatment were studied.
Average post-Kpro follow-up was 7.1 months. Pre-KPro, 76.9% of patients were known to have glaucoma - 35.9% had had previous glaucoma surgery and 43.5% were on glaucoma medication. Post-Kpro, 84.6% of patients were deemed to have glaucoma, whether progressive or static, and 79% of patients were on IOP-lowering medication. 3 patients necessitated surgical treatment of uncontrolled IOP; 2 underwent Ahmed tube implantation followed by pars plana vitrectomy combined with endocyclophotocoagulation, while the third underwent transcleral cyclophotocoagulation. 9 of the 33 patients with glaucoma (27.2%) had progression of glaucoma post-operatively. 14 patients (35.8%) had VA limited to some extent by glaucoma, 6 of which had a VA of counting fingers (CF) or worse; of these, 2 patients had good VA initially (20/40 and 20/50), then progressed to end-stage glaucoma, whereas the other 4 patients already had end-stage glaucoma with poor vision.
Most KPro candidates are known to have preoperative glaucoma. Extent of visual improvement post-KPro is therefore often unpredictable. Good initial visual outcome does not preclude the need for rigorous monitoring for glaucoma progression. Patients require tight control of IOP, which is complicated by a lack of objective tonometry, leaving clinicians to rely on digital palpation to monitor pressure. Serial VFs are therefore paramount, as is repeat optic nerve examination with serial stereoscopic photographs when possible. The incidence of glaucoma progression has led us to conclude that a very low threshold should be used to treat suspicion of even slightly elevated IOP.
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