Retroprosthetic membrane: A complication of keratoprosthesis with broad consequences

Keratoprosthesis (KPro) devices have the remarkable ability to restore vision in patients suffering from corneal blindness who are poor candidates for traditional penetrating keratoplasty. However, eyes with KPro can experience various complications, including the development of retroprosthetic membrane (RPM). RPMs reduce visual acuity in patients due to physical obstruction of the visual axis, but studies have shown that RPM can also lead to a variety of other consequences, from melting of the corneal carrier graft to precipitating retinal detachments. Histopathologic studies have shown that RPMs are composed of elements from both the recipient and donor. The presence of myofibroblasts in RPMs imparts them with contractile properties, which can contribute to their downstream complications, including angle closure, hypotony, and retinal detachment. At present, there are limited treatments to combat the growth of RPM. Future therapies could include anti-metabolites and targeted anti-inflammatory treatments, as well as device coatings or textured device surfaces that can hinder RPM proliferation. The long-term success of KPro depends on devising an effective solution for preventing RPM growth.     

临时人工角膜用于玻璃体切除术

目的 探讨临时人工角膜（ＴＫＰ）用于玻璃体切除术治疗严重眼外伤的意义。方法 以ＴＫＰ取代浑浊角膜后，行闭合式玻璃体切除术。最后行穿透性角膜移植术，治疗外伤性玻璃体视网膜病变合并角膜浑浊８眼，结果首次手术成功率７／８，随访２至１０月，平均４月，视力进步７眼，下降１眼，最佳者随访半年维持０．３。结论 应用ＴＫＰ，一期重建眼球结构，恢复部分视功能，为此类病例的盲眼复明提供了新途径。     

Medium term results in keratoprostheses with biocompatible and biological haptic

Purpose Corneal grafts or limbal stem cell transplantation are often unsuccessful in patients with severe ocular surface disorders such as severe dry eye syndrome, symblepharon or diffuse vascularisation. In those patients, a keratoprosthesis (KPro) may be an alternative for the recovery of vision. Various KPro differ from each other in the material of the haptic that supports the optic cylinder. The haptic may be made of biocompatible or biological material such as tibia bone (TKPro) or dentine and alveolar bone (osteo-odonto-keratoprosthesis, OOKP). On the basis of our experience, we wanted to comment on the value of different KPro.Methods Over the last 10 years we have implanted a total of 35 KPro, 29 with biological haptic (25 OOKP and four TKPro), and six KPro with biocompatible haptic (one Legais KPro, five Pintucci KPro). A follow up examination was carried out approximately every6 months.Results The patients gained a visual acuity of ≥0.9 in 20.6%, of ≥0.5 in 52.9%, of ≥0.2 in 61.8% and a significant improvement in visual acuity in 76.5%, respectively. There was no significant difference between the various types of KPro concerning the best postoperative visual acuity. All patients showing poor improvement had a pre-existing end stage secondary glaucoma or other retinal damage. The median follow-up was 2.9 years (maximum 8) for OOKP, 1 year for TKPro, 1 year (maximum 2) for Pintucci Kpro and 6 month for Legeais KPro. During this period, only one of the KPro with biological haptic was lost (one TKPro after 1 year), compared with four out of six of the KPro with biocompatible haptic (P<0.0001).Conclusions Fixation of the KPro by a root of the patient´s own tooth (OOKP) leads to the best results in the long-term follow up, as our results as well as the literature demonstrate. As long as a KPro is in place, the visual acuity is as good as the retinal function. For the ranking of different types of KPro, the percentage and the duration of the anatomic success are most important. The comparability of the various KPro results may be limited, since the patients were not randomised and the four groups differ in number.Presented at the 102. Congress of the Deutschen Ophthalmologischen Gesellschaft, Berlin.     

自体角膜为载体Boston人工角膜治疗复杂性角膜盲

目的评价复杂性角膜混浊患者使用自体角膜做载体的BostonI型人工角膜植入的临床效果。方法回顾性病例研究。10例角膜盲患者（10眼）,术眼病变严重,经至少2名以上国内著名角膜病专家会诊。无法通过角膜移植复明。其中严重碱烧伤7眼,爆炸伤1眼,角膜内皮失代偿多次角膜移植失败1眼．双眼病毒性角膜炎角膜严重血管化1眼。其中9例为双眼盲。术前视力光感或手动。所有病例均一期完成手术,术中使用8．0mm或8．5mm环钻钻取患者角膜,用患者混浊病变的角膜为载体。安装Boston人工角膜。形成患者角膜．人工角膜复合体,复合体作为植片如传统角膜移植实行角膜植床和植片缝合固定,术中常规行晶状体摘除术。结果术后观察1-12个月,平均（5．7±3．8）个月,除1眼视力光感外,其余裸眼视力为0．1～0．8。手术并发症包括角膜植床出血人玻璃体腔2例,继发性青光眼2例,人工角膜后膜4例。所有术眼均无术后漏水并发症发生。结论人工角膜特别适合于穿透性角膜移植难于成功的角膜盲患者,而且是目前对严重角膜瘢痕血管化、眼睑或泪液功能不良患者有效的复明手段。我国角膜供体严重匮乏,用自体角膜为载体可作为部分BostonI型人工角膜植入手术的可行方案。     

软性一体式 PHEMA人工角膜植入碱烧伤兔角膜的电镜观察

目的：研究与评估新型软性一体式PHEMA人工角膜与碱烧伤兔角膜生物愈合的电镜特点。方法制备兔角膜碱烧伤模型后,将软性一体式PHEMA人工角膜植入,分别于4周、8周、16周和24周后取裙边组织进行扫描电镜和透射电镜检查。结果4周时,即有新生组织长入孔隙之中,材料与角膜组织结合紧密;迁徙入材料内的角膜细胞胞浆富含粗面内质网等细胞器,显示旺盛的合成功能;其周围有胶原、蛋白多糖等细胞外基质的沉积,并且显示出从新生到成熟的动态变化。结论新型人工角膜的孔隙支架材料,能够允许角膜细胞及周围组织迁徙、增殖并分泌沉积细胞外基质,从而达到材料与组织的生物愈合。     

Boston Type 2 keratoprosthesis- mid term outcomes from a tertiary eye care centre in India

To analyse the anatomical and functional outcomes of Boston type II keratoprosthesis at a tertiary eye care centre in South India. Retrospective chart review of 10 patients operated with Boston keratoprosthesis Type 2 between Feb 2013 and June 2017 were analysed. Outcome measures analysed included, visual outcome, device retention and postoperative complications. The most common indication for surgery was SJS in 80% (8 of 10 eyes). Mean follow-up duration was 2.75 years (0.5–5 years, SD?-?1.71, median 32 months) Postoperative visual acuity improved to better than 20/200 in 7 eyes and better than 20/30 in 6 eyes with device retention in 9 eyes at last follow-up. Pre-existing glaucoma was noted in 1 eye. RPM was noted in 1 eye, retinal detachment in 1 eye, endophthalmitis in 1 eye and sterile melt requiring kpro replacement in 1 eye. No progression or development of glaucoma was noted postoperatively in any eye . Boston type 2 keratoprosthesis is a viable option to restore vision in patients with end stage ocular surface disorders. Though the procedure can be associated with complications, early as well as late, our midterm outcome appears to be encouraging.     

软性一体式PHEMA人工角膜植入碱烧伤兔角膜的电镜观察

目的 研究与评估新型软性一体式PHEMA人工角膜与碱烧伤兔角膜生物愈合的电镜特点。方法 制备兔角膜碱烧伤模型后,将软性一体式PHEMA人工角膜植入,分别于4周、8周、16周和24周后取裙边组织进行扫描电镜和透射电镜检查。结果 4周时,即有新生组织长入孔隙之中,材料与角膜组织结合紧密;迁徙入材料内的角膜细胞胞浆富含粗面内质网等细胞器,显示旺盛的合成功能;其周围有胶原、蛋白多糖等细胞外基质的沉积,并且显示出从新生到成熟的动态变化。结论 新型人工角膜的孔隙支架材料,能够允许角膜细胞及周围组织迁徙、增殖并分泌沉积细胞外基质,从而达到材料与组织的生物愈合。     

Predictive factors of Boston Type I Keratoprosthesis outcomes: A long-term analysis

PurposeTo study the long-term visual- and device retention-related outcomes and complications of the Boston Type I Keratoprosthesis (KPro).MethodsSingle-center, retrospective cohort study of all patients undergoing KPro implantation from February 2007 to April 2014 with at least 5 years of follow-up.Results68 eyes from 65 patients underwent KPro implantation during the study period. At 5 and 10 years, the probability of maintaining or improving visual acuity (VA) was 75.0% and 66.7%, respectively, and the probability of KPro retention was 89.2% and 89.2%, respectively. Initial device retention rate at 10 years was significantly lower in those with underlying ocular surface disease (46.8% [30.6–63.2] vs 75.8% [61.0–90.7], P = 0.03), while other baseline characteristics showed no significant association. Final VA was more likely to be stable or improved in patients with fewer failed grafts (2 [1–6] vs 3 [1–6], P < 0.01), and a final VA of 20/200 or better was more likely in primary KPro eyes (44.8% [26.7–62.9] vs 19.4% [6.5–32.3], P = 0.03). Combined KPro-vitrectomy eyes were more likely to have stable or improved final VA than non-vitrectomy eyes (88.5% [76.2–100.0] vs 64.1% [49.1–79.1], P = 0.04). All complications had increasing incidence beyond 5 years; in particular, corneal melt, surgical glaucoma interventions, and endophthalmitis tended to have late presentations, with 79.0%, 78.6%, and 88.9% of these complications occurring beyond one year, respectively.ConclusionsKPro devices show favorable long-term visual and retention outcomes in select patients. Careful long-term, multidisciplinary follow-up is warranted to address potential complications.     

The evolution of the modified osteo-odonto-keratoprosthesis,its reliability,and long-term visual rehabilitation prognosis: An analytical review

An exhaustive search of the world's literature was performed to analyze all case reports and series on the modified osteo-odonto-keratoprosthesis (MOOKP) published up to January 2022. The demographic profile, the primary indication for surgery, surgical technique variations, postoperative medical management, long-term functional and anatomical outcomes, and intra- and postoperative complications were analyzed and compared. Additionally, some of the authors' (GI, VP, and GA) unpublished MOOKP cases were studied. An extensive literature search yielded 37 case series and case reports. Overall, 958 patients were analyzed. The most common indication for surgery was autoimmune disease (39.1%), closely followed by chemical injury (38.8%). The most common intraoperative complications (21.67%) included maxillofacial, vitreous hemorrhage/vitritis, and mucosal. The most common postoperative complications (78.4%) were lamina and oral mucosa-associated, secondary glaucoma, and choroid/retinal detachment. Follow-up periods ranged from one to 364 months (median: 36.7 months). Altogether, 78% of patients achieved a visual acuity of 20/400 or better at the end of the follow-up period, and 91.2% improved at least temporarily after MOOKP surgery. Mean anatomic success at the end-of-follow-up for all patients was 88.25% (range, 50–100%). The long-term anatomic and functional success of the MOOKP makes it a reliable option for visual rehabilitation in patients with bilateral corneal blindness and end-stage ocular surface disease. This review aims to describe the evolution of the MOOKP procedure, analyzing all published case series for its long-term reliability, visual and anatomical outcomes, complications, and future directions.     

Long-term functional and anatomical results of osteo- and osteoodonto-keratoprosthesis

PURPOSE: To analyse the functional and anatomical results of keratoprosthesis using tooth and tibial autograft. METHODS: We reviewed 227 charts of patients that underwent osteo-keratoprosthesis (OKP) (n = 82) or osteo-odonto-keratoprosthesis (OOKP) (n = 145) at the Centro de Oftalmología Barraquer. Mean follow-up time was 8.4 years for OOKP and 3.5 years for OKP. Kaplan-Meier survival curves with 95% confidence interval (CI) were calculated for functional success, defined as BCVA >0.05. Anatomical success was defined as retention of the keratoprosthesis lamina. Visual Acuity by Time (VAT) Index with 95% CI was calculated for up to 2 years post-OKP and up to 6 years post-OOKP. Maximum visual acuity ever reached after the last step of the implantation of the keratoprosthesis was used as an indicator for the potential of the retina. RESULTS: Based on Kaplan-Meier analyses, 10-year anatomical survival was 66% (CI 57-76) for OOKP and 47% (CI 27-67) for OKP. Two-year functional survival was 63% (CI 55-71) for OOKP and 49% (CI 37-60) for OKP, and 10-year functional survival was 38% (CI 29-48) for OOKP and 17% (CI 5-28) for OKP. Multivariate analysis showed that neither surgical technique (OOKP or OKP), primary diagnosis nor age had a significant influence on the functional survival. However, a high maximum visual acuity ever reached post-op decreased the risk for functional failure. According to the VAT Index calculations, mean BCVA 2 years after OOKP was 0.33 (CI 0.28-0.41) and after OKP was 0.28 (CI 0.20-0.36). CONCLUSION: Although we found a tendency that OOKP had better anatomical results than OKP, this difference was not statistically significant up to 10 years post-op. Functional results for both techniques were not significantly different at the 2-year follow-up, but at 10 years they were. However, this difference was influenced by the retinal potential and not by the technique itself.