Safety of unwrapped spherical orbital implants

PURPOSE: To determine the exposure rate of unwrapped spherical orbital implants after enucleation surgery. METHODS: Retrospective review of consecutive case series. All patients undergoing orbital implantation during enucleation surgery from October 1999 to September 2003 were included. Charts were reviewed for preoperative diagnoses, type and size of implant, use of a wrapping material, and complications. RESULTS: Twenty-six consecutive patients underwent enucleation surgery without wrapping material. Nineteen patients received porous polyethylene, 5 patients received polymethylmethacrylate, and 2 received hydroxyapatite. Mean implant diameter was 21.03 mm. Mean follow-up was 17.1 months (range, 2 to 43 months). There were no complications of implant extrusion, exposure, infection, or migration. CONCLUSIONS: The use of unwrapped spherical orbital implants may be associated with a low rate of early exposure. Careful choice of implant type may help reduce the risk of implant exposure.     

Histologic evaluation of corneal stroma in rabbits after intrastromal corneal ring implantation

PURPOSE: Previous refractive corneal implants have produced histologic changes characteristic of nonspecific lipid keratopathy. Intacs intrastromal corneal ring segments are polymethylmethacrylate (PMMA) corneal inserts approved for the correction of low myopia by the U.S. Food and Drug Administration. The purpose of this study was to describe histologic changes associated with these corneal implants in rabbit eyes. METHODS: Two 150-degree PMMA arc segments, 0.30 mm thick, were surgically implanted through a single radial incision at two-thirds stromal depth in the mid-peripheral cornea of five New Zealand white rabbits. We collected corneas 6 months after implantation that were prepared for light and electron microscopy. We analyzed tissue with oil red O, filipin, and periodic acid-Schiff (PAS) staining. Additional studies with energy-dispersive x-ray analysis and autofluorescent microscopy were conducted. RESULTS: In all samples, we observed new collagen formation with lamellar organization adjacent to the implant and increased keratocyte density. Intracellular accumulations of osmophilic and saturated lipid material corresponded to stromal opacification visible by slit-lamp microscopy. These same regions were autofluorescent and stained positively with oil red O, and filipin but negatively with PAS. Granular lipid inclusions characteristic of lipofuscinosis were absent on transmission electron microscopy. Energy-dispersive x-ray analysis demonstrated elevated levels of calcium compared with adjacent tissue. CONCLUSION: Tissue response to these corneal inserts includes keratocyte activation, intracellular lipid accumulation, and new collagen formation. Our histologic findings suggest that these deposit formations are not lipofuscin accumulations.     

Comparison of the effect of polymethylmethacrylate and silicone intraocular lenses on rabbit corneal endothelium in vitro

An in vitro comparison of corneal endothelial damage caused by polymethylmethacrylate and by silicone intraocular lenses was made. Endothelial damage was assessed by vital staining of corneal endothelium immediately following direct contact with an intraocular lens. Silicone lenses produced less damage than polymethylmethacrylate lenses. The difference could be attributed to a specific type of damage-membrane stripping-seen only after contact with polymethylmethacrylate lenses.     

A tectonic keratoprosthesis using expanded polytetrafluoroethylene as a supporting skirt in humans.

A tectonic keratoplasty was performed with a keratoprosthesis using expanded polytetrafluoroethylene as a supporting skirt, on the left eye of a 23-year-old woman who needed an emergency corneal transplantation due to corneal perforation. The keratoprosthesis implanted, consisted of a supporting skirt which was made of expanded polytetrafluoroethylene (PTFE), and an optic portion which was made of polymethylmethacrylate (PMMA). The optic portion and the supporting skirt were attached by cyanoacrylate tissue adhesive (Histoacryl). Two months post-operatively, the keratoprosthesis was extruded, leaving an opacified, vascularized cornea. A penetrating keratoplasty was performed 1 month later. The excised cornea was composed of granulation tissue. To our knowledge, this is the first case of tectonic keratoprosthesis using expanded PTFE as a supporting skirt in humans.     

Clinicopathologic correlation of explanted AlphaCor artificial cornea after exposure of implant

PURPOSE: To describe the clinical presentation and histopathologic findings in a case of explantation of an AlphaCor artificial cornea implant caused by exposure of the skirt. METHODS: We describe the case report of a 46-year-old man who suffered trauma to the right eye, resulting in 4 failed penetrating keratoplasties (PKPs). Subsequently, an AlphaCor implantation was performed with some visual improvement. Slightly more than 2 years after the implant, skirt exposure occurred, possibly secondary to infectious keratitis in an area of a ruptured bulla, and explantation was performed. Corneal stability was established with repeat corneal transplantation. RESULTS: Histopathologic evaluation of the surgical specimen revealed chronic nongranulomatous inflammation and fibrosis in the peripheral skirt, indicating that biointegration was maintained. However, peripheral corneal stromal melting led to skirt exposure. Focal calcification, as well as retroprosthetic membrane formation, was also identified. CONCLUSIONS: The AlphaCor implant is a viable method of treatment for multiple failed PKPs, but it may be associated with unique complications, including corneal stromal melting, focal calcification, and retroprosthetic membrane formation. Infectious keratitis may be a risk factor for corneal stromal melting and needs to be managed aggressively. Explantation of the implant is essential if the skirt is exposed.     

CxGELSIX: a novel preparation of type VI collagen with possible use as a biomaterial

PURPOSE: This study was initiated to evaluate tissue acceptance and stability of a novel type VI collagen preparation (CxGelsix) as a biomaterial in the rabbit corneal stroma. We hypothesized that CxGelsix, embedded intrastromally, does not have any adverse affect on surrounding corneal tissues, and remains intact in the presence of an acute inflammatory reaction during corneal wound healing. METHODS: Type VI collagen was extracted and purified from rabbit corneal stroma under nondenaturing conditions. This preparation, Gelsix, was concentrated and cross-linked with polyethylene glycol to produce a transparent film (CxGelsix). Discs of CxGelsix, 4.0-mm diameter, 9- to 35-microm thick were implanted intrastromally and clinically examined periodically for 4 months. In another experiment, implantation of CxGelsix, 2.0-mm-diameter, was followed by corneal wounding adjacent to the implant and examined clinically for 30 weeks. At the end of these periods, the tissues from these experiments were processed for light and transmission electron microscopy. RESULTS: An intralamellar 4.0-mm-diameter disc of CxGelsix does not alter the structure of corneal epithelium above the implant, suggesting normal transport of nutrients through CxGelsix. Moreover, no structural abnormalities were seen in the rest of the cornea, and the cornea remains transparent. Although the cornea accepts the presence of CxGelsix disc as judged by clinical criteria, gradual degradation of the implant is seen ultrastructurally. CxGelsix is remarkably stable despite its exposure to endogenous enzymes during inflammation and wound healing. Partial degradation of the implant occurs only after many months, and it is gradually replaced with bundles of fine collagen fibrils reminiscent of normal cornea. CONCLUSION: The results of this study suggest that CxGelsix is potentially useful as a biomaterial.     

Bilateral lagophthalmos in lepromatous leprosy. Case report

CASE REPORT: A case of bilateral facial palsy with paralytic ectropion, lagophthalmos and corneal damage secondary to corneal exposure in a long-standing patient with lepromatous leprosy is presented. Correction of paralytic ectropion was performed by medial cantoplasty, tarsal strip and Medpor lower eyelid spacer implantation. Lagophthalmos was corrected by gold weight implant in the upper tarsus. DISCUSSION: Ocular findings in leprosy appear in 72% of patients. Facial nerve palsy occurs in 3-19.8%, being bilateral in 5%. In long standing cases with corneal complications secondary to exposure, surgical treatment is required.     

Amniotic membrane to the rescue of partially necrosed dermis fat graft

A 25-year-old woman underwent dermis fat graft on the right side for persistent ocular pain with her polymethylmethacrylate (PMMA) spherical orbital implant. One week later she developed dermal necrosis of the dermis fat graft with potentially devastating fat atrophy if left uncovered. Amniotic membrane graft epithelial side up was sutured to the conjunctiva surrounding the fat. 2 weeks later the graft epithelialized with preservation of fat. Role of amniotic membrane graft as a routine lining over dermis fat grafts to promote conjunctival healing and prevent fat exposure needs to be studied in prospective studies.     

Histological study of graft failure in AlphaCor transplantation

To report clinical and histopathologic findings in a case of a failed AlphaCor artificial cornea explanted due to corneal stromal melting. We describe the case of a 77-year-old man who received multiple penetrating keratoplasties (PKPs) and subsequent placement of an AlphaCor artificial cornea. Examination showed total corneal infiltration as well as an AlphaCor that was partially dehisced from the host cornea. After explantation, the implant and adjacent host tissue underwent hematoxylin and eosin staining and high-resolution scanning electron microscopy (HR-SEM). Histopathologic analysis of the specimens revealed infiltration of the skirt pores by reactive corneal fibroblasts. Although the AlphaCor implant is an established method of treating multiple failed PKPs, in this case, HR-SEM imaging strongly suggests that the strength of the interface between the implant and corneal tissue is highly dependent on collagen deposition between the pores found in the implant skirt. Collagen deposition then increases the mechanical strength of the cornea–skirt interface.     

Effects of rigid contact lens truncation on oxygen access to the central cornea under static and dynamic conditions

Truncation is most commonly used for stabilization of bifocal and toric front surface lenses. Lenses with small edge defects also can be truncated and polished rather than being discarded. The purpose of this study was to determine whether corneal physiology is compromised when truncated lenses are worn. Contact lenses were manufactured with three amounts of truncation (0, 0.2, and 0.4 mm) in two contact lens materials (polymethylmethacrylate and itabisfluorofocon A). All lenses were fitted “on K” on the right eye of each of six subjects, with all other parameters kept constant. As expected, central corneal oxygen uptake rates measured with the itabisfluorofocon A material were significantly lower, indicating less hypoxic stress or oxygen deprivation, than those measured with polymethylmethacrylate across conditions (nonblink and blink) and amounts of truncation. No significant differences in central corneal oxygen uptake were found among amounts of truncation across conditions and materials.     

Behavior of various orbital implants under axial compression

PURPOSE: To determine and compare the amount of force required to disrupt the integrity of various orbital implants. METHODS: Compression tests were carried out by using a servo-electrical universal testing system on orbital implants including aluminum oxide (Bioceramic implant, FCI, Issy-Les-Moulineaux, France), coralline hydroxyapatite (HA) (Bio-Eye, Integrated Orbital Implants, Inc., San Diego, CA, U.S.A.), bovine HA (Molteno M-Sphere, IOP Inc., Costa Mesa, CA, U.S.A.), synthetic HA (FCI3, FCI, Issy-Les-Moulineaux, France), Chinese HA (H + Y Comprehensive technologies, Philadelphia, PA, U.S.A.), polylactic acid (Kinsey Nash Corporation, Duluth, MN, U.S.A.), porous polyethylene (Medpor, Porex Surgical Inc., College Park, GA, U.S.A.), and polymethylmethacrylate. RESULTS: Two basic groups of implants were identified: those that eventually reach a critical compression point and collapse (coralline HA, aluminum oxide, synthetic FCI3 HA, bovine HA, Chinese HA, and polymethylmethacrylate), and those that do not collapse but gradually compress with increasing load (porous polyethylene, polylactic acid). For similar-sized implants, the critical collapse point was earliest for the FCI3 HA implant, followed by the coralline HA, aluminum oxide, and polymethylmethacrylate implants. Smaller-sized collapsible implants showed earlier critical collapse points than larger-sized implants of similar material. CONCLUSIONS: A technique was established to assess the force required to disrupt the integrity of various orbital implants that is reliable, unbiased, and repeatable with any orbital implant. Orbital implants of different materials and sizes demonstrate different degrees of integrity. It is important to use similar-sized implants when comparing the integrity of different implant materials because size influences the force required to overcome the structural integrity of the implant.     

Hard contact lens-induced corneal neovascularization treated by oxygenation.

A 39-year-old man suffered from corneal neovascularization, through to result from hypoxia caused by improper use of polymethylmethacrylate (PMMA) hard contact lenses. The condition was successfully treated by oxygenation of the corneas under swimming goggles.     

New Dacron tissue colonisable keratoprosthesis: clinical experience.

BACKGROUND--Keratoprostheses (KPs) are made of an optical cylinder integrated with a supporting element which conditions their biocompatibility. A new KP with a Dacron tissue colonisable support has been designed in order to reduce significantly the complication rate. METHODS--This new KP was implanted into 20 eyes of 20 patients with bilateral corneal blindness unsuited to a corneal implant. The follow up ranged from 24 to 96 months. RESULTS--All 20 patients had some improved visual acuity with 13 retaining this improvement for more than 2 years. CONCLUSION--These favourable results may be indicative of the reliability of the new KP.     

组织工程角膜基质的体外构建及移植的实验研究

目的探讨利用组织工程技术体外构建角膜基质进行板层角膜移植的可行性和有效性。方法将猪角膜基质去细胞处理后制备成组织工程角膜基质载体;取幼兔角膜基质细胞体外培养,将其种植在载体上,体外构建成组织工程角膜基质,用PKH26荧光标记兔角膜基质细胞示踪角膜基质的构建;将16只兔的角膜基质内植入壳聚糖膜使之形成无菌性角膜溃疡,随机从16只兔中选8只,进行组织工程角膜基质移植;另外8只作为对照组,进行新鲜的同种异体兔板层角膜移植。术后对角膜进行裂隙灯、光学显微镜、透射电镜观察。结果体外构建的组织工程角膜的基质细胞具有活性,其结构与正常角膜基质相近。移植治疗无菌性角膜溃疡术后,1~2周有新生血管侵入组织工程角膜基质植片边缘,植片为灰白色半透明状;3~4周随着新生血管减退,组织工程角膜基质植片局部开始透明变薄;术后8~10周角膜溃疡完全修复,角膜恢复透明性,角膜神经可再生;观察最长达10月,角膜仍保持透明,无免疫排斥发生,与对照组疗效相同。结论体外构建的组织工程角膜基质无免疫原性、具有良好的生物相容性,可作为临床治疗角膜溃疡的移植材料。     

Corneal edema and permanent blue discoloration of a silicone intraocular lens by methylene blue.

BACKGROUND AND OBJECTIVE: To report a silicone intraocular lens (IOL) stained blue by inadvertent intraoperative use of methylene blue instead of trypan blue and the results of experimental staining of various lens materials with different concentrations of the same dye. MATERIALS AND METHODS: A "blue dye" was used to enhance visualization during capsulorhexis in a patient undergoing phacoemulsification with implantation of a three-piece silicone lens. Postoperatively, the patient presented with corneal edema and a discolored IOL. Various IOL materials were experimentally stained using methylene blue. Sixteen lenses (4 silicone, 4 hydrophobic acrylic, 4 hydrophilic acrylic, and 4 polymethylmethacrylate) were immersed in 0.5 mL of methylene blue at concentrations of 1%, 0.1%, 0.01%, and 0.001%. These lenses were grossly and microscopically evaluated for discoloration 6 and 24 hours after immersion. RESULTS: The corneal edema resolved within 1 month after the initial surgical procedure. After explantation, gross and microscopic analyses of the explanted silicone lens revealed that its surface and internal substance had been permanently stained blue. In the experimental study, all of the lenses except the polymethylmethacrylate lenses were permanently stained by methylene blue. The hydrophilic acrylic lenses showed the most intense blue staining in all dye concentrations. CONCLUSIONS: This is the first clinicopathological report of IOL discoloration due to intraocular use of methylene blue. This and other tissue dyes may be commonly found among surgical supplies in the operating room and due diligence is necessary to avoid mistaking these dyes for those commonly used during ocular surgery.     

Topographic changes in contact lens-induced corneal warpage

Twenty-one eyes of 12 patients with contact lens-induced corneal warpage were followed prospectively using computer-assisted topographic analysis. Sixteen eyes had worn rigid contact lenses (13 eyes, polymethylmethacrylate; three eyes, gas-permeable), and five eyes had worn soft contact lenses. Initial corneal topographic patterns were characterized by the presence of central irregular astigmatism, loss of radial symmetry, and frequent reversal of the normal topographic pattern of progressive flattening of corneal contour from the center to the periphery. A correlation was noted between the initial corneal topography and the resting position of the contact lens on the cornea for nine of the 16 eyes with rigid contact lenses. Initial topography for each of these corneas showed relative flattening of the corneal contour underlying the resting position of a decentered contact lens. Superior-riding lenses produced a topography that simulated early keratoconus. After cessation of contact lens wear, 16 of 21 eyes had a change in corneal shape to a topography that was consistent with a normal pattern. Five corneas stabilized with an abnormal topographic pattern. A much longer time without contact lenses than had been previously reported, up to 5 months, was required for a return of a stable corneal topography in eyes with contact lens-induced corneal warpage caused by rigid lenses.     

Post-septal upper eyelid loading for treatment of exposure keratopathy secondary to non-cicatricial lagophthalmos

Exposure keratopathy may result in ocular surface dryness, pain, corneal ulceration and loss of vision. Upper eyelid loading is an effective surgical treatment for paralytic lagophthalmos but has been criticised for complications of implant exposure and poor cosmesis. We therefore reviewed the safety and efficacy of our technique of upper eyelid post-septal loading for exposure keratopathy in this context. A retrospective case notes analysis was undertaken of 38 patients who had upper eyelid loading, all with post-septal weight placement, for correction of lagophthalmos. Patient demographics, indications for surgery, outcomes and complications were analysed. The mean age of all patients was 59.6 years. Exposure keratopathy was secondary to facial nerve paralysis in all but two patients, with tumor excision being the commonest underlying aetiology (63.8%). The mean implant weight used was 1.4 grams. Pre-operatively, all 38 patients had ocular discomfort despite maximal use of lubricating eye drops but post-operatively, 29 patients (76.3%) were comfortable without any such drops. Mean lagophthalmos on blink and gentle closure improved from 7.42mm and 5.47mm pre-operatively to 2.18mm and 1.18mm post-operatively (p < 0.001). Similarly, before surgery all patients had some corneal staining but after surgery 37 patients (97.4%) had none. The gold weight was removed in four patients (10.5%), due to chronic inflammation in three and due to mild astigmatism in one. No patient had exposure of the weight and one patient had a ptosis repair 6 months after surgery. Upper eyelid loading was effective in reducing both signs and symptoms of exposure keratopathy related to lagophthalmos in our series. Patients were very satisfied with the surgical outcome and complications related to exposure and cosmesis were very rare.     

The effects of high-Dk rigid contact lens center thickness, material permeability, and blinking on the oxygen uptake of the human cornea.

PURPOSE: The human corneal oxygen uptake responses associated with the static (nonblinking) and dynamic (blinking) wear of five rigid gas-permeable materials with high oxygen permeabilities were determined for three different center thicknesses and compared with the responses for the normal open eye and severe hypoxic stress (static wear of polymethylmethacrylate). METHODS: Corneal oxygen uptake rates were measured with a Clark-type polarographic electrode during two sessions with each of 10 human subjects. Measurements were made on the right eye for the normal open eye (air) and after 5 minutes of static and dynamic wear of polymethylmethacrylate and five rigid gas-permeable contact lens materials: Fluoroperm 92 (paflufocon A, Dk = 92), Fluoroperm 151 (paflufocon D, Dk = 151), 1992 Menicon SF-P (melafocon A, Dk = 102), 1995 Menicon SF-P (melafocon A, Dk = 159), and Menicon Z (tisilfocon A, Dk = 163-250). Lenses were manufactured in three different center thicknesses (0.12, 0.16, and 0.20 mm), with all other parameters remaining constant. Repeated-measures analysis of variance was used and included lens material (five levels), blinking condition (two levels), and lens thickness (three levels) as within-subject effects. RESULTS: Significant differences were found in corneal oxygen responses to lens material (p < 0.001) and lens thickness (p < 0.001), with lenses of lower oxygen permeability and thicker lenses being associated with higher oxygen uptake. No statistically significant differences were noted between static or dynamic wear of the lens materials (p = 0.59). CONCLUSIONS: For those very high Dk rigid lens materials studied here, moderate changes in lens thickness or material permeability may result in modest differences in corneal hypoxic relief, whereas blinking results in no significant improvement to corneal oxygenation.     

Posterior auricular muscle patch graft for exposed orbital implant

The purpose of this article is to describe a surgical technique to repair an exposed orbital implant by posterior auricular muscle autograft. A retrospective review was conducted of four patients with an exposed orbital implant that were treated with a posterior auricular muscle graft. Four patients received posterior auricular muscle patch graft to the exposed orbital implant. The donor site healed with minimal scarring and remained well hidden. The graft incorporated fully into surrounding orbital tissue with no recurrent exposure at average of 13 month follow-up. The posterior auricular muscle autograft is a viable technique for repairing an exposed orbital implant.     

环孢素A缓释系统植入前房抑制鼠角膜移植免疫排斥反应机制的研究

目的　探讨前房植入环孢素A(cyclosporineA ,CsA)缓释系统抑制鼠角膜移植免疫排斥反应的机制。方法　 (1)环孢素A缓释系统的制备 :为CsA粉剂与已交酯 丙交酯 已内酯的三元共聚物混合体 ,每粒含环孢素A 0 5mg。 (2 )对 90只 (90只眼 )BALB c鼠 (受体 )行穿透性角膜移植术 ,将其分为A、B、C组 ,每组 30只。供体为C5 7BL 6鼠。A组术中鼠前房植入CsA缓释系统 ;B组术中鼠前房植入不含CsA的空白缓释系统 ;C组术后不作任何处理作为正常对照组。术后 3d用裂隙灯显微镜观察角膜植片情况 ,记录角膜植片免疫排斥反应发生的时间和程度。各组分别于术后 1、2、4及 6周随机取 2只鼠眼行组织病理学检查 ,并用CD4、CD8及CD11B单克隆抗体行免疫组织化学染色 ,观察各组T淋巴细胞的迁移和数量。结果　A组鼠角膜植片排斥时间平均 (35± 3)d ,较B、C组 (14± 3)d明显延长 (P <0 0 0 1)。前房植入的CsA缓释系统体积缩小前 ,A组角膜植片均保持透明 ;当前房植入的CsA缓释系统消失后 ,角膜出现免疫排斥反应 ,植片逐渐混浊、增厚、血管化。B、C组免疫排斥反应均在术后 2周发生。组织病理学和免疫组织化学检查 :A组在术后 14d仅于植床角膜可见少量CD+ 4 　和CD+ 8　细胞浸润 ,在虹膜和睫状体中未见CD+ 11B、CD+ 4 、CD+ 8　T淋