Glaucoma after corneal replacement

Glaucoma is a well-known complication after corneal transplantation surgery. Traditional corneal transplantation surgery, specifically penetrating keratoplasty, has been slowly replaced by the advent of new corneal transplantation procedures: primarily lamellar keratoplasties. There has also been an emergence of keratoprosthesis implants for eyes that are high risk of failure with penetrating keratoplasty. Consequently, there are different rates of glaucoma, pathogenesis, and potential treatment in the form of medical, laser, or surgical therapy.     

Experimental study on the biocompatibility of keratoprosthesis with improved titanium implant

AIM: To investigate whether hydroxyapatite (HAp) coating can improve keratoprosthesis (KPro) implant biointegration, ultimately to decrease the risk of implant-associated complications. METHODS: The modified titanium implant was designed and prepared for artificial cornea. The titanium implant was treated with sandblasting and hydroxyapatite coating by acid-base two-step method. Surface was analyzed by scanning electron microscopy (SEM), KPro implants coated with HAp and KPro implant sandblasted were implanted in rabbits. Tissue adhesion to the implant was assessed and compared to an unmodified implant by histopathology (HE), transmission electron microscopy (TEM) and SEM. RESULTS: SEM demonstrated successful deposition of HAp on titanium implant sandblasted (HA/SB-Ti). The hydroxyapatite coatings caused enhancement of keratocyte proliferation compared with unmodified implant surfaces. HAp coating significantly increased adhesion forces. HAp coating of implants reduced the inflammatory response around the KPro implants in vivo. CONCLUSION: HAp-coated surfaces for use in titanium KPro implant greatly enhanced adherence of the titanium KPro implant in the rabbit cornea.     

A novel temporary keratoprosthesis technique for vitreoretinal surgery

AIM: To investigate the safety of vitreoretinal surgery when using a soft contact lens as a temporary keratoprosthesis (TKP) in patients with severe corneal opacifications. METHODS: Three patients with simultaneous corneal and vitreoretinal pathology were treated with a soft contact lens that was used as a TKP to facilitate vitreoretinal surgery. The soft contact lens was fixated with sutures onto the globe so that no leakage was possible. RESULTS: Vitreoretinal surgery with excellent fundus view was possible in all cases. The soft contact lens allowed safe central and peripheral vitrectomy. Surgery was successful in all cases. CONCLUSION: A soft contact lens properly fixated on the globe can successfully replace a TKP. This surgical procedure has several advantages like one size fits all, low costs, and easy access to the material.     

Clinical Features and Prognosis of Boston Type I Keratoprosthesis-associated Corneal Melt

Purpose: To describe the clinical features and outcomes of corneal melt associated with Boston type I keratoprosthesis (KPro) implantation.

Methods: Medical records of patients who experienced corneal melt following KPro implantation were reviewed retrospectively.

Results: Sixty-six adult patients had KPro implantation from January 2004 to November 2010. Six patients had an underlying inflammatory ocular surface disorder. Four experienced corneal melt (6.1%) 5–42 months after the initial surgery. One patient was diagnosed with Sjögren’s syndrome as a result of diagnostic workup following melt. Three patients were treated with systemic immunomodulatory therapy; two experienced fungal keratitis and subsequent endophthalmitis. KPro had to be explanted and replaced with donor cornea in all cases.

Conclusions: KPro-associated corneal melt is uncommon and appears to occur in patients with preexisting inflammatory disorders, which might not have been previously diagnosed. Timely explantation of KPro and replacement with donor cornea may prevent a poor outcome.     

Boston keratoprosthesis and Ahmed glaucoma valve for visual rehabilitation in congenital anterior staphyloma

Congenital anterior staphyloma entails grave visual prognosis. The majority of reported patients have undergone enucleation. We report a promising result of staphylectomy with implantation of a keratoprosthesis and a glaucoma drainage device in a seven-month-old child with a large, congenital anterior staphyloma.     

羟基磷灰石表面修饰人工角膜钛支架的生物相容性：电镜观察

背景：人工角膜是双眼角膜盲患者复明的希望,提高人工角膜材料的生物相容性使人工角膜与宿主角膜达到生物愈合是目前人工角膜的研究方向。 目的：扫描电子显微镜观察经羟基磷灰石表面修饰能否增加人工角膜纯钛支架的生物相容性。 方法：采用酸碱两步预处理法在人工角膜钛支架表面快速沉积羟基磷灰石涂层。将第4~6代兔角膜基质成纤维细胞直接接种于羟基磷灰石修饰的钛支架、纯钛支架及玻璃表面,3,24,48,72 h后,扫描电子显微镜观察材料表面的细胞黏附,伸展及增殖情况;将18只正常新西兰白兔随机分为2组,于右眼角膜基质层内分别植入羟基磷灰石修饰的钛支架、纯钛支架,术后6,12周取出人工角膜支架,扫描电子显微镜观察材料表面角膜组织贴附生长状态。 结果与结论：体外实验显示,细胞接种3 h和24 h后,细胞扩展面积及细胞张力丝长度：羟基磷灰石修饰的钛支架>玻璃>纯钛表面,羟基磷灰石修饰的钛支架表面的活细胞数多于其他材料表面(P < 0.05)。72 h后,羟基磷灰石修饰的钛支架表面完全被胶原覆盖。体内实验显示,扫描电子显微镜观察羟基磷灰石修饰的钛支架表面细胞外基质生长良好,与羟基磷灰石贴附紧密。而纯钛支架仅为角膜组织简单包裹。说明人工角膜纯钛支架经羟基磷灰石表面修饰后,其生物相容性增加。 关键词：人工角膜;羟基磷灰石;钛;表面改性;生物相容性;扫描电子显微镜 doi:10.3969/j.issn.1673-8225.2010.29.007     

In vivo biological stability of chemically pretreated silicone gel inserts intended for use in keratoprostheses

Background The previous study showed that pretreatment with chemical agents could alter the surface chemistry of the silicone gel making it suitable for epithelial migration onto its surface and enhancing the cytobiocompatibility. The Purpose of this study was to evaluate the biological response of the cornea stroma to porous silicone gel pretreated with different chemical agents in vivo. Methods The porous silicone gels were treated with mixed acid solution containing 23.2% H2SO4 and 0.8% K2Cr2O7 for 10 or 15 minutes or with 30% H2O2 for 15 minutes. Discs (4 mm in diameter) were inserted into interlamellar stromal pockets of New Zealand white rabbits and followed for a period of 3 months. Clinical evaluations such as corneal infiltration, oedema and neovascularisation were performed daily. At 3 months, the fibroplasias and collagen deposition were examined under light and scanning electron microscopy (SEM) and by immunohistochemical analysis. Results Pretreatment of the discs obviously decreased conjunctival congestion, discharge, cornea oedema, and the extent of neovascularization. More fibroblasts migrated into the pretreated discs than into the control, and collagen was deposited, indicating that the biocompatibility of the corneal replacements was enhanced by the chemical pretreatments. From immunohistochemical analysis, Type I collagen deposition in the pretreated silicone discs was greater than that in the control. Conclusions Chemical treatment of silicone gel is effective in decreasing rabbit corneal inflammation, encouraging fibroblast ingrowth and enhancing tissue compatibility, thus the pretreated gels show good biological stability when used as a skirt material in Keratoprosthesis (Kpros).     

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.     

Keratoprosthesis: preliminary results of an artificial corneal button as a full-thickness implant in the rabbit model

Purpose: To develop a prototype artificial cornea and evaluate it in the rabbit model.
Methods: Hydrogel core-and-skirt keratoprostheses were made and were inserted as full-thickness implants covered with conjunctival flaps in the right eyes of eight rabbits.
Results: Peroperative complications related to inadequate mechanical strength led to failure in the early postoperative period in three animals, one was euthanased for an unrelated reason and the remaining four have been successful for up to 16 weeks' follow-up.
Conclusions: Full-thickness implantation of an artificial cornea; analogous to penetrating keratoplasty, has been achieved in the rabbit model. Histological findings confirm that integration of the prosthesis with host tissue occurs. The main complications encountered in this preliminary series were related to inadequate strength of the sponge skirt of this prototype device. Work in our laboratories is now concentrated upon improving the mechanical qualities of the hydrogel skirt and on the enhancement of biointegration.