Vitreoretinal Complications of the Boston Keratoprosthesis

Abstract

The Boston Keratoprosthesis has allowed for visual restoration in patients with corneal blindness; however, vitreoretinal complications remain a significant cause of ocular morbidity. Retroprosthetic membranes, infectious endophthalmitis, sterile vitritis, vitreous hemorrhage, vitreous opacities, retinal detachment, cystoid macular edema, choroidal detachments, retinal vascular occlusion, and epiretinal membrane have all been described, may require the intervention of a vitreoretinal specialist, and are reviewed herein. A strong familiarity with associated posterior segment complications is important to maximizing patient outcomes.     

The Boston Keratoprosthesis in severe ocular trauma

BACKGROUND: In eyes with corneal disease and opacity so severe that standard corneal transplantation carries a poor prognosis, a keratoprosthesis (KPro) may still be successful in providing functional visual acuity. The purpose of this study was to determine the outcome of Boston KPro implantation in the rehabilitation of severe ocular trauma. METHODS: This is a retrospective study of 30 eyes (30 patients) with severe ocular trauma that underwent Boston KPro type I implantation at the Massachusetts Eye and Ear Infirmary. Of these 30 eyes, 6 had mechanical trauma, 21 had chemical burns, and 3 had thermal burns. The measures used in this review are 5-fold: (i) anatomic success; (ii) number of postoperative repair procedures performed; (iii) preoperative and postoperative visual acuity; (iv) number of eyes with concomitant preoperative retinal or optic nerve damage prior to KPro surgery; and (v) incidence of postoperative complications. RESULTS: Preoperative visual acuity ranged from counting fingers to light perception (median: hand motion). Best-corrected postoperative visual acuity ranged from 20/20 to no light perception (median: 20/80). Anatomic success was achieved in 5 out of 5 mechanically traumatized eyes, 14 out of 17 eyes with chemical burns, and 3 out of 3 eyes with thermal burns. Repair procedures were done in 8 of the 17 chemically burned eyes. The number of eyes with concomitant preoperative ocular disease was 2 out of 6 in the mechanical trauma group, 10 out of 21 in the chemical burn group, and 1 out of 3 in the thermal burn group. The incidence of postoperative complications was greater in the chemical burn group than in either the mechanical trauma or the thermal burn group. INTERPRETATION: The Boston KPro can provide considerable visual improvement and a long-term anatomic retention rate in severely traumatized eyes. The overwhelming danger in severe chemical burns is glaucoma progression despite a functioning tube implant and normal intraocular pressure.     

A Review of Corneal Melting after Boston Keratoprosthesis

Abstract

Use of the Boston Keratoprosthesis (B-KPro) has grown significantly, both in the United States and overseas over the course of the last decade. It is the most frequently employed keratoprosthesis for the management of complex corneal blindness. Improving outcomes and reductions in devastating complications such as corneal melting and infection have motivated this increase in use. We review the epidemiology and pathophysiology of corneal melting following B-KPro as well as the advances in B-KPro design and postoperative care that have halted the occurrence of melting. Eyes with autoimmune diseases such as Stevens-Johnson syndrome, toxic epidermal necrolysis syndrome, and mucous membrane pemphigoid remain particularly vulnerable to corneal melt, leak, and extrusion. The development of new strategies to prevent melting in eyes with autoimmune disease is crucial to improve the outcomes of this group of patients, as they are often those with the most desperate need for visual rehabilitation with a B-KPro.     

Pars plana vitrectomy through the Boston Keratoprosthesis type 1

Purpose

To ascertain the feasibility of pars plana vitrectomy (PPV) through a permanent Boston Keratoprosthesis type 1 (KPro) without the use of a temporary KPro.

Methods

A retrospective interventional case series. Eyes implanted with Boston KPro type 1 between 2008 and 2011 requiring PPV for vitreoretinal complications were included. Feasibility of PPV through the KPro, its anatomical and functional success were studied.

Results

Five out of 70 patients required PPV for vitreoretinal complications post-KPro surgery resulting in an incidence of 7%. PPV was feasible through the Boston KPro with no deleterious effects on the corneal carrier or the KPro itself. Repeat PPV was necessary in some cases. Although anatomical repair of the vitreoretinal complications was achieved in most cases, post PPV visual acuity remained poor in the majority.

Conclusion

Our study suggests that although PPV through the Boston KPro is a viable approach for vitreoretinal disease repair, visual rehabilitation remains poor.     

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。     

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.     

Importance of nutrition to corneal grafts when used as a carrier of the Boston Keratoprosthesis

PURPOSE: Necrosis, melt, and perforation have historically been frequent around a Keratoprosthesis (KPro), even resulting in extrusion or endophthalmitis. Autoimmune diseases such as Stevens-Johnson Syndrome (SJS) and Ocular Cicatricial Pemphigoid (OCP) have been notorious in this respect. The purpose of this study was to compare the frequency of tissue melt after implantation of two designs of the Boston KPro, one allowing much better access of nutrition from the aqueous humor to the carrier graft. METHODS: We retrospectively reviewed charts of 157 eyes implanted since 1990 with a poly (methylmethacrylate) Boston KPro, including 79 eyes implanted with the model having 8 small (1.3-mm diameter) holes in the back plate, and 78 eyes implanted with the older solid back plate. We compared the frequency of tissue melts between the two KPro designs, for all implants as well as for subgroups based on preoperative diagnosis. RESULTS: In total, 48/157 eyes (31%) developed some degree of tissue melt around the stem, including 8/79 eyes (10%) in the back plate with holes group and 40/78 eyes (51%) in the solid back plate group (P < 0.0001). Among the melts in the back plate with holes group, 4/8 (50%) suffered from an underlying autoimmune disease such as SJS or OCP. CONCLUSIONS: The Boston KPro design with a back plate containing holes protects the overlying corneal tissue from necrosis and melts. This improved situation is likely due to increased aqueous access and better nutrition to the corneal graft cells. In addition, this study confirms earlier work regarding the particular corneal fragility of patients with autoimmune diseases.