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Glaucoma Management of Glaucoma Following Boston Keratoprosthesis Gargi Khare Vora and Kathryn A Colby Massachusetts Eye and Ear Infirmary, Department of Ophthalmology, Harvard Medical School, Boston, Massachusetts, US Abstract Boston keratoprosthesis (KPro) surgery has revolutionised the treatment of corneal and ocular surface disease. At present, glaucoma is the most important vision-threatening complication following KPro surgery. Diagnosis of glaucoma in KPro patients is difficult since the current method of determining intraocular pressure (IOP) by digital palpation is subjective and dependent upon the skill of the examiner. Optic nerve evaluation and visual field testing are important tools to follow glaucoma progression. Management of glaucoma following Boston KPro consists of medical therapy and surgical options. Glaucoma drainage devices are useful in this population but can have a variety of complications. Cyclophotocoagulation, either the non-invasive transscleral method or endocyclophotocoagulation, is also useful as an adjunctive measure in glaucoma management. Appropriate diagnosis and management of glaucoma is essential after KPro surgery to reduce the chance of vision loss. Keywords Keratoprosthesis, glaucoma, intraocular pressure, Ahmed valve Disclosure: The authors have no conflicts of interest to declare Received: 5 January 2012 Accepted: 5 March 2012 Citation: European Ophthalmic Review, 2012;6(4):214–7 Correspondence: Kathryn A Colby, Cornea and Refractive Surgery, Massachusetts Eye and Ear Infirmary, Department of Ophthalmology, Harvard Medical School, 243 Charles Street, Boston, MA 02114, US. E: KAColby@meei.harvard.edu The explosion of Boston keratoprosthesis (KPro) surgery over the last 10 years has revolutionised the field of cornea and ocular surface disease. Options for patients with severe inflammation of the corneal and conjunctival surface were limited prior to the development of the KPro surgical technique by Dohlman et al. 1 The Type 1 KPro, which is most frequently used, has a collar button design consisting of two plates joined by a stem, which forms the optical portion (see Figure 1). A fresh donor graft is used as a carrier for the device and a soft contact lens is placed over the ocular surface. The Type 2 Boston KPro is similar in design except that the 2 mm optical portion protrudes through a tarsorrhaphy. 2 The Boston KPro allows for dramatic and rapid visual improvement in patients whose ocular disease is confined to the anterior segment. 3 In the past, vision loss following Boston KPro could result from a number of complications including infection, corneal melting and retinal detachment. Modifications in device design and post-operative management have reduced the occurrence of these problems. At present, glaucoma is the most important threat to long-term preservation of vision following Boston KPro surgery. 4–6 Appropriate diagnosis and management of glaucoma following Boston KPro is vital to ensure the best outcomes. Pre-operative Glaucoma Many patients who are candidates for Boston KPro surgery have pre-existing glaucoma. Previous case series from multiple institutions have shown a prevalence of pre-operative glaucoma of between 36 and 76 %. 5–10 This is not surprising since patients who need a Boston KPro have often had multiple prior corneal surgeries or have diseases that cause intraocular inflammation, necessitating topical, subtenon 214 or systemic glucocorticoids. 2 Steroid-response ocular hypertension is prevalent among these patients, which can contribute to the development of glaucoma. 11 In addition, various ocular diseases have individual factors that can contribute to ocular hypertension and glaucomatous optic neuropathy. Akpek et al. reported a case series of 15 patients with aniridic keratopathy who underwent KPro placement in which 14 patients (93 %) were diagnosed with glaucoma pre-operatively. 12 Aniridic patients have abnormal angle structures that predispose the eye to glaucoma. Iris stubs can contribute to secondary angle closure, further increasing intraocular pressure (IOP). In a case series of 17 eyes with herpetic keratitis, Khan et al. found that 66 % of eyes had pre-operative co-morbid glaucoma. 13 Herpes simplex virus can cause trabeculitis, which also contributes to elevated IOP. Sayegh et al. reported 75 % of their patients with Stevens-Johnson syndrome (SJS) undergoing KPro placement had pre-operative glaucoma. The authors hypothesised that damage to the anterior segment structures by inflammation and scarring from SJS contributed to glaucoma development. 14 The most severe cases of pre-operative glaucoma are caused by chemical burns. In a series of 28 eyes with chemical burns, 21 eyes (75 %) had evidence of pre-operative glaucoma or ocular hypertension. 15 Alkali burns penetrate deeper than acidic burns, and cause scarring in the drainage angle, and even injury to the retina. Progressive optic nerve damage typical of glaucoma has even been reported in patients with normal IOP, thought to be secondary to ganglion cell layer damage due to alkali. 15 Harissi-Dagher et al. observed that there is often risk of advancing glaucoma even after © TOUCH MEDICAL MEDIA 2012