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      Keratoprostheses for corneal blindness: a review of contemporary devices

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          Abstract

          According to the World Health Organization, globally 4.9 million are blind due to corneal pathology. Corneal transplantation is successful and curative of the blindness for a majority of these cases. However, it is less successful in a number of diseases that produce corneal neovascularization, dry ocular surface and recurrent inflammation, or infections. A keratoprosthesis or KPro is the only alternative to restore vision when corneal graft is a doomed failure. Although a number of KPros have been proposed, only two devices, Boston type-1 KPro and osteo-odonto-KPro, have came to the fore. The former is totally synthetic and the latter is semi-biological in constitution. These two KPros have different surgical techniques and indications. Keratoprosthetic surgery is complex and should only be undertaken in specialized centers, where expertise, multidisciplinary teams, and resources are available. In this article, we briefly discuss some of the prominent historical KPros and contemporary devices.

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          Global data on visual impairment in the year 2002.

          This paper presents estimates of the prevalence of visual impairment and its causes in 2002, based on the best available evidence derived from recent studies. Estimates were determined from data on low vision and blindness as defined in the International statistical classification of diseases, injuries and causes of death, 10th revision. The number of people with visual impairment worldwide in 2002 was in excess of 161 million, of whom about 37 million were blind. The burden of visual impairment is not distributed uniformly throughout the world: the least developed regions carry the largest share. Visual impairment is also unequally distributed across age groups, being largely confined to adults 50 years of age and older. A distribution imbalance is also found with regard to gender throughout the world: females have a significantly higher risk of having visual impairment than males. Notwithstanding the progress in surgical intervention that has been made in many countries over the last few decades, cataract remains the leading cause of visual impairment in all regions of the world, except in the most developed countries. Other major causes of visual impairment are, in order of importance, glaucoma, age-related macular degeneration, diabetic retinopathy and trachoma.
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            Corneal neovascularization as a risk factor for graft failure and rejection after keratoplasty: an evidence-based meta-analysis.

            Preoperative corneal neovascularization (CNV) is thought to be associated with an increased rate of corneal graft failure and potentially also graft rejection. New therapeutic options that offer differential influence on the ingrowths or regression of either corneal blood or lymphatic vessels force us to re-evaluate the known data about the role of CNV in keratoplasty. Electronic databases and corneal registries were searched (up through September 2008). Results were reported both descriptively for each study and using random effects meta-analysis. Potential moderating factors for the association between vascularization and graft failure and rejection were examined using metaregression analysis. Nineteen studies reporting on a total of 24,944 grafts undergoing keratoplasty were included. An increase in the risk of graft failure and rejection in the presence of pathologic CNV was seen in studies with a pooled risk ratio of 1.32 (95% confidence interval [CI], 1.15-1.49) for graft failure and 2.07 (95% CI, 0.98-3.15) for graft rejection. There was evidence of incremental increase of risk for graft failure and rejection as more corneal quadrants were affected by neovascularization. The 2 factors predictive of increased risk of neovascularization and graft failure were increased recipient age (P = 0.003) and male gender (P = 0.046). Graft failure and rejection risk increase with an increasing number of corneal quadrants affected by neovascularization before keratoplasty. These data support the study of novel topical antiangiogenic therapies at the cornea to precondition such a cornea for future corneal grafting. Proprietary or commercial disclosure may be found after the references. Copyright 2010 American Academy of Ophthalmology. Published by Elsevier Inc. All rights reserved.
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              Long-term outcome of keratolimbal allograft with or without penetrating keratoplasty for total limbal stem cell deficiency.

              To evaluate the long-term outcome of ocular surface reconstruction, including keratolimbal allograft (KLAL) and amniotic membrane transplantation (AMT) with or without penetrating keratoplasty (PKP), in patients with nonambulatory vision secondary to total limbal stem cell deficiency (LSCD). Retrospective, non-comparative interventional case series. Thirty-nine eyes in 31 consecutive patients with total LSCD, as defined by impression cytology, who had a preoperative best-corrected visual acuity of less than 20/200 and a minimum follow-up of 12 months. Patients were divided into three groups: group 1 (16 eyes) with chemical burns, group 2 (9 eyes) with Stevens-Johnson syndrome (SJS), and group 3 (14 eyes) with other causes of LSCD, including ocular cicatricial pemphigoid, atopic keratoconjunctivitis, and aniridia. All patients underwent KLAL and AMT by one surgeon (SCGT). If needed, PKP was performed at the same surgical setting using tissue from the same donor. Cumulative rates of survival of ambulatory vision (> or = 20/200), survival of KLAL, survival of PKP, and incidence of complications. Fifty-three KLAL with AMT procedures were performed in 39 eyes, of which 23 eyes received simultaneous PKP at the time of the first KLAL. The mean follow-up was 34.0 +/- 21.5 months (range, 12-117.6). The mean period of ambulatory vision was 23.9 +/- 20.9 months (range, 0-104). The overall survival of ambulatory vision was 53.6% at 3 years and 44.6% at 5 years. The survival of ambulatory vision was significantly worse in SJS compared with other causes (67%, 81%, and 92% for groups 1, 2, and 3, respectively; P = 0.06 for group 1 versus 2, P = 0.0008 for group 1 versus 3). KLAL performed alone resulted in higher survival of ambulatory vision at 2 years (86.1% +/- 9.1%) compared with KLAL with PKP (46.9% +/- 10.6%, P = 0.100). The survival of PKP was significantly worse in SJS compared with the other causes (20.0% +/- 17.9% compared with 55.6% +/- 11.7%, respectively, P = 0.028). After 2 years, the survival of the second KLAL was better than that of the first: 68.2% +/- 15.4% compared with 27.3% +/- 13.4%, respectively (P = 0.041). Ambulatory vision for a period of more than 2 years can be achieved by KLAL with or without PKP in eyes with severe ocular surface disorders caused by total LSCD. However, a progressive decline of the visual outcome and graft survival is evident with time. Performing PKP simultaneously with KLAL may be associated with a less favorable outcome. The failure of KLAL is associated with the loss of donor cells in the recipient. Augmentation of ocular surface defense is essential in securing the success of KLAL and PKP. Future modifications of the surgical procedure and of the immune suppressive protocols may improve survival of the allogeneic grafts and the final visual outcome.
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                Author and article information

                Journal
                Clin Ophthalmol
                Clin Ophthalmol
                Clinical Ophthalmology
                Clinical Ophthalmology (Auckland, N.Z.)
                Dove Medical Press
                1177-5467
                1177-5483
                2015
                16 April 2015
                : 9
                : 697-720
                Affiliations
                [1 ]Sussex Eye Hospital, Brighton, UK
                [2 ]Brighton and Sussex Medical School, Brighton, UK
                [3 ]Tongdean Eye Clinic, Hove, UK
                Author notes
                Correspondence: Christopher Liu, Sussex Eye Hospital, Eastern Road, Brighton BN2 5BF, UK, Tel +44 1273 606126, Fax +44 1273 693674, Email cscliu@ 123456aol.com
                Article
                opth-9-697
                10.2147/OPTH.S27083
                4406263
                25945031
                97574e35-f24c-42c2-ad90-d2fb5f1ce3b9
                © 2015 Avadhanam et al. This work is published by Dove Medical Press Limited, and licensed under Creative Commons Attribution – Non Commercial (unported, v3.0) License

                The full terms of the License are available at http://creativecommons.org/licenses/by-nc/3.0/. Non-commercial uses of the work are permitted without any further permission from Dove Medical Press Limited, provided the work is properly attributed.

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                Review

                Ophthalmology & Optometry
                keratoprosthesis,ookp,kpro,boston kpro,cornea,ocular surface
                Ophthalmology & Optometry
                keratoprosthesis, ookp, kpro, boston kpro, cornea, ocular surface

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