Implantation of an inactive epiretinal poly(dimethyl siloxane) electrode array in dogs

The aim of this study is to investigate the long-term, mechanical biocompatibility of a polymer microtechnology that can be used to position electrodes in close proximity to the retina. Poly(dimethylsiloxane) (PDMS) arrays were manufactured by soft-lithography at Lawrence Livermore National Laboratory. The PDMS implant measured 4 mm x 40 mm x 55-60 microm and included 4-8 electrodes. Micromolded ribs were placed at the perimetry for strength and ease of manipulation. The PDMS arrays were implanted epiretinally in four normal dogs, with a single retinal tack used in each case to hold the device on the retina. The mechanical effects of the implant were followed up after surgical implantation by photography, fluorescein angiography, optical coherence tomography (OCT), and electrophysiologic tests. An intraoperative retinal tear occurred in the first implanted dog, causing retinal detachment and necessitating termination. The remaining dogs experienced no gross complications secondary to the array implantation procedure. During the follow-up period of 2 months in one eye and 6 months in three eyes, OCT demonstrated that the arrays were in close contact with the retina. Fluorescein angiography showed good perfusion of the retina under the array. At the end of 6 months, there was no statistical difference from baseline in mean retinal thickness under the array (P=0.43) or peripapillary retinal nerve fibre layer thickness corresponding to the implanted area (P=0.34). The mean distance between the array and the retinal surface varied from 32 to 68 microm throughout the follow-up. Histopathologic evaluation of the retinal implantation site in eyes followed for 6 months showed a general preservation of the normal, layered retinal structure, except for some localized retinal thinning in two eyes, where the array frame had been in direct retinal contact. The PDMS substrate micro array is a new and promising technology that can be scaled to support a high-density retinal stimulating array. Its implantation and handling is surgically manageable, and it forms a mechanically stable, acceptable interface with the inner retinal surface.     

Intrusion of retinal tacks

We examined nine patients in whom retinal tacks intruded into the eye and lodged in the subretinal space, preretinal space, vitreous cavity, or anterior chamber. Complications included retinal pigment epithelium atrophy; retinal phlebitis; vitreous hemorrhage; focal corneal, iris, and retinal injury; and corneal edema. The intrusion of the retinal tacks did not apparently cause, but was associated with retinal redetachment in five patients. Factors associated with intrusion of the retinal tacks included absence of a barb at the end of the tack to anchor it to the sclera, absence of a groove in the tack, a short shaft, incomplete penetration of the retina, choroid, and sclera by the tack, self-inflicted trauma to the eye, placing a scleral buckle after inserting the tacks, and reproliferation of periretinal membranes. In four patients the intruded tacks did not cause any complications. In four patients the intruded tacks were removed without complications and in the remaining five patients, they were left in the eye.     

Fibrovascular response to retinal tacks in the rabbit and monkey eye

In order to evaluate the tissue response to metal retinal tacks experiments were carried out on 4 monkey eyes and compared to those on 4 rabbits. Non-magnetic retinal tacks (Grieshaber, Switzerland) and tacks made of 24 carat gold (our own brand) were inserted into the ocular fundus under microscopic control. The animals were kept for 3 months. In monkey eyes, histological examination disclosed a considerable fibrovascular proliferation around the retinal tack canal, including an inflammatory response, formation of collagenous tissue and glial proliferation. There was a local intra-retinal and epi-retinal neovascularization. In the rabbit retina, only a slight inflammation and thin collagenous tissue developed. Thus the tissue response was much more severe in the primate eye than in the avascular rabbit retina.     

Enucleated eye model for intraocular retinal prosthesis implantation.

An enucleated porcine eye model was developed to assess intraocular retinal prosthesis implantation surgery. The surgical technique consists of corneal and crystalline lens removal, keratoprosthesis replacement, and vitrectomy. To test the eye model, the scleral incision was increased to 5 mm and a 10-mm wide retinal prosthesis folded and inserted. One retinal tack was used to fix the prosthesis to the retina. A retinal prosthesis array was inserted without significant damage to the array and conformed to the curvature of the eye. Fundus photography and optical coherence tomography were performed at the end of surgery.     

Long-term histologic and electrophysiologic evaluation of the alloy retinal tack

The retinal tack is a useful adjunctive instrument in the repair of complicated retinal detachments. To examine the tissue response of chronically implanted alloy tacks, we implanted a series of tacks into rabbit eyes. Their effects were observed at 1 and 4 weeks, at 6 months, and at 2.5 years after insertion. Our observations indicate that the histology and electrophysiology of the retina was generally not affected. All tacks were surrounded by connective and/or glial tissue scar and induced firm retinal adherence. The retinal architecture was normal within 1 mm of the scar; indicating that these alloy tacks do not cause tissue damage outside the immediate area of the wound, even when left in place over a period of 2 years.Supported by Grieshaber and Company and by Research to Prevent Blindness, (Langhorne, Pa., New York, N.Y.) Offprint requests to: E. de Juan     

兔眼滤过性手术中植入硅凝胶膜的实验研究(英文)

目的:在兔眼行硅凝胶膜植入后,通过观察眼内压、滤过泡、病理组织检查结果评价硅凝胶膜植入的安全性和有效性。方法:共40只兔随机分为4组,每组10只。每只兔一眼行巩膜瓣下小梁咬切术,术中植入硅凝胶膜,对侧眼单纯行巩膜瓣下小梁咬切术作为对照。术后观察眼内压、滤过泡的变化,并且每只眼行组织病理学检查。结果:植入眼较对照眼低眼压和滤过泡维持时间长,光镜显示植入眼滤过道、咬切口区保持通畅。成纤维细胞增殖的活性与规律,在植入眼和对照眼是相似的。硅凝胶膜不会刺激成纤维细胞增殖的过度表达。结论:硅凝胶膜植入术作为一种新型引流术具有安全、有效、操作简单的优点。     

兔眼滤过性手术中植入硅凝胶膜的实验研究

目的：在兔眼行硅凝胶膜植入后，通过观察眼内压、滤过泡、病理组织检查结果评价硅凝胶膜植入的安全性和有效性。 方法：共40只兔随机分为4组，每组10只。每只兔一眼行巩膜瓣下小梁咬切术，术中植入硅凝胶膜，对侧眼单纯行巩膜瓣下小梁咬切术作为对照。术后观察眼内压、滤过泡的变化，并且每只眼行组织病理学检查。 结果：植入眼较对照眼低眼压和滤过泡维持时间长，光镜显示植入眼滤过道、咬切口区保持通畅。成纤维细胞增殖的活性与规律，在植入眼和对照眼是相似的。硅凝胶膜不会刺激成纤维细胞增殖的过度表达。 结论：硅凝胶膜植入术作为一种新型引流术具有安全、有效、操作简单的优点。     

Management of subretinal foreign bodies with a cannulated extrusion needle

We treated two patients who had nonmagnetic subretinal foreign bodies (metallic pellet and lens nucleus fragment) in the presence of a retinal detachment and a distant retinal break. After the pars plana vitrectomy, the soft, flexible tip of the cannulated extrusion needle was used to push the foreign object gently away from the posterior pole toward the retinal break where it was grasped and removed from the eye. This technique for subretinal foreign body removal is preferable to creating a large posterior retinotomy overlying the foreign body because of the potential risks of further macular trauma, hemorrhage, or proliferation of periretinal membranes from the retinotomy site.     

Long-term histological and electrophysiological results of an inactive epiretinal electrode array implantation in dogs.

PURPOSE: Short-term pattern electrical stimulation of the retina via multielectrode arrays in humans blind from photoreceptor loss has shown that ambulatory vision and limited character recognition is possible. To develop an implantable retinal prosthesis that would provide useful vision, these results need to be sustained over a prolonged period of retinal electrical stimulation. As a first step toward this goal, the biocompatibility and the feasibility of surgically implanting an electrically inactive electrode array onto the retinal surface was tested. METHODS: A 5 x 5 electrode array (25 platinum disc-shaped electrodes in a silicone matrix) was implanted onto the retinal surface using retinal tacks in each of the 4 mixed-breed sighted dogs. Color fundus photography, fluorescein angiography, electroretinography, and visual evoked potentials were obtained preoperatively, at 1-week intervals for 2 weeks postoperatively, then at 2-week intervals up to 2 months postoperatively, and thereafter at 1-month intervals. One dog was killed at 2 months after implantation and a second dog after 3 months of implantation. Histologic evaluation of the retinas was performed. The remaining two dogs continue to be followed beyond 6 months after the implantation surgery. RESULTS: No retinal detachment, infection, or uncontrolled intraocular bleeding occurred in any of the animals. Retinal tacks and the retinal array remained firmly affixed to the retina throughout the follow-up period. Hyperpigmentation of the retinal pigment epithelium was observed only around the site of retinal tack insertion. No fibrous encapsulation of the implant or intraocular inflammation was visible. A- and b-wave amplitudes of the electroretinogram were depressed at the first postoperative week testing but recovered over the ensuing 1 week and were not statistically different from the normal unoperated fellow eye throughout the postoperative period. N1 and P1 wave amplitudes of the visual evoked potentials were not significantly different from the normal fellow eyes at any of the postoperative test intervals. Fluorescein angiography showed that the entire retina including the area under the electrode array remained well perfused. Similarly, histologic evaluation revealed near total preservation of the retina underlying the electrode array. CONCLUSIONS: Implantation of an electrode array on the epiretinal side (i.e., side closest to the ganglion cell layer) is surgically feasible, with insignificant damage to the underlying retina. The platinum and silicone arrays as well as the metal tacks are biocompatible. With the success of implanting an electrically inactive device onto the retinal surface for prolonged periods, the effects of long-term retinal electrical stimulation are now ready to be tested as the next step toward developing a prototype retinal prosthesis for human use.     

Two retinal vein occlusions in a patient with venous tortuosity at the optic disc

Background The aetiology of occlusion is thought to differ for branch retinal vein and central retinal vein types. This communication reports on an unusual presentation of two retinal vein occlusions in one eye of a patient with optic disc tortuosity where the occlusion was thought to occur at a site usually seen in central retinal vein occlusion. Methods An 88-year-old woman presented with sudden-onset painless loss of central vision. Fundal examination of the affected eye revealed one infero-temporal retinal vein occlusion affecting the macula and a second vein occlusion affecting the supero-nasal quadrant with associated optic disc tortuosity. She was investigated for cardiovascular risk factors. Results Treatment had already been started for systemic hypertension and blood markers were unremarkable. Conservative management was recommended. 12 weeks later, fluorescein angiography showed no ischaemia. Conclusion We report an unusual case of two co-existent and opposing retinal vein occlusions where obstruction was thought to occur at the trunk of the central retinal vein at or near the level of the lamina cribrosa, a site usually associated with the formation of hemi-vein or central retinal vein occlusion. This had occurred as a result of tortuous vasculature at the optic disc. This unusual case lends weight to previously suggested hypotheses of retinal vein occlusion. The authors have no financial or proprietary interest in any product mentioned in this article     

Retinal fixation of traumatic retinal detachment with metallic tacks: a case report with 10 years' follow-up

BACKGROUND: Retinal rupture and detachment caused by traumatic ocular perforation has a poor prognosis without extensive repair procedures. The authors describe the phases of treatment of a complex injury in a 21-year-old man with a traumatic retinal rupture in whom metallic tacks were used for retinal fixation. The report does not include histopathology. METHODS: Observational case report and literature review. The outcome of a 10-year follow-up is evaluated at the latest visit by determining the visual acuity (VA) and by observing the state of retina and tacks. RESULTS: A traumatic retinal rupture with detachment was treated with titanium tacks for retinal fixation. By inserting a total of 13 metallic tacks for the repair of a temporal postequatorial retinal rupture and adjacent retinal detachment a successful outcome was achieved. Two additional operations were performed to reattach the retina of nasal hemisphere in the same eye. One dislodged tack was removed at the final operation. Ten years later, at the last intervention, VA was 12/20 in the injured eye. The retina was completely attached, and the remaining 12 tacks were in place, although six of them were partially pushed up by an encircling band. Proliferative vitreoretinopathy (PVR) was absent, and a relatively narrow circumferential zone of scar tissue adjacent to the row of tacks was visible. The patient occasionally experienced glare in the affected eye, but was otherwise symptom-free. CONCLUSION: Reports of long-term experiences with mechanical retinal refixation with metallic tacks are scarce. Especially in extended use, the tacks are claimed to cause several complications, including PVR. Although modern ophthalmic surgery offers a variety of methods for retinal reattachment, the complexity of the damage caused by trauma may lead to a dead end in refixation attempts. Nevertheless, retinal tacks may represent an adjunctive remedy in complex retinal detachment cases.     

Macular rotation with and without counter-rotation of the globe in patients with age-related macular degeneration

· Background: Macular rotation to treat exudative age-related macular degeneration (AMD) involves translocation of the fovea to a site with intact retinal pigment epithelium. To avoid the inevitable postoperative cyclotropia we combined this procedure with torsional muscle surgery. · Patients and methods: In 30 eyes the macula was rotated upward by 30–50° following complete artificial retinal detachment and a 360° retinotomy. Simultaneous torsional muscle surgery was not carried out in the first 8 eyes; in the remaining 22 eyes surgery of the oblique muscles was performed alone or in combination with surgery of two or four rectus muscles. Simultaneously or later, muscle surgery was performed on the fellow eye in 17 of these patients. Three of the eight patients who had no primary muscle surgery were operated on later. They had muscle surgery on the macular-rotated eye and on the fellow eye. · Results: Postoperatively, the silicone oil was removed from all but one eye and an intraocular lens implanted in all but two eyes. Five eyes developed a postoperative retinal detachment, three of them with proliferative vitreoretinopathy. Three other eyes developed a recurrence of the choroidal neovascularization. At last examination, 18 of the 30 eyes (60%) had a near vision of 0.4 or better, sufficient for the reading of normal newsprint. Six of the eight patients who did not undergo muscle surgery reported considerable disorientation caused by the postoperative diplopia and cyclotropia. The muscle operation, which has been performed in a total of 25 patients, conferred complete freedom from complaints in all but one patient. · Conclusion: Macular rotation succeeded in restoring reading vision in about half of cases of exudative AMD, at least in the short term. The most serious complication was the development of a retinal detachment. The extremely disorienting side effects of diplopia and tilted image could be prevented or effectively treated by muscle surgery for counter-rotation of the globe, if need be also in the fellow eye. Received: 16 September 1998 Revised version received: 27 November 1998 Accepted: 30 November 1998     

Experimental posterior penetrating eye injury in the rabbit. II. Histology of wound, vitreous, and retina.

The histological findings of the wound, the vitreous, and the retina in the rabbit eye with experimental posterior penetrating injury are described. Wound healing had just begun at 3 days after injury and was well established by 9 to 12 days. It involved proliferation of cells from the episclera and from the choroid. The progression to a fibrous ingrowth from the wound occurred only in eyes with blood in the vitreous. The intravitreal fibroblastic proliferation had begen at 6 days after injury and seemed to be derived from the choroid, the nonpigmented ciliary epithelium and, posteriorly, from the optic nervehead. During the development of retinal detachment the configuration of the peripheral and posterior retina, together with the orientation of vitreous strands, suggested the presence of vitreous traction. We postulate that the presence of contractile fibroblasts (myofibroblasts) in the vitreous may provide the mechanism for vitreous traction. The retinal detachments were also characterised by epiretinal and subretinal membranes, but these were not prominent. The end-stage appearance of a soft, shrunken eye with cyclitic membrane formation and retinal detachment resembles the outcome in many human eyes after severe penetrating injuries.     

Massive retinal gliosis: an unusual case with immunohistochemical study

Massive retinal gliosis (MRG) is a rare, benign intraocular condition that results from the proliferation of well-differentiated glial cells. Immunohistochemically, these cells show positivity for glial fibrillary acid protein (GFAP), neuron specific enolase (NSE), and S-100 protein. We encountered a case of a 45-year-old female with loss of vision in the left eye. She had a history of trauma to that eye two years ago. Enucleation was carried out, because malignancy was suspected due to retinal calcification. On the basis of light microscopy and immunohistochemistry (IHC) performed on the enucleated eye, it was diagnosed as massive retinal gliosis.     

Phacoemulsification of the crystalline lens and implantation of an intraocular lens for the correction of moderate and high myopia: four-year follow-up

PURPOSE: To assess the safety of lens extraction and intraocular lens (IOL) implantation in patients with high myopia treated for initial lens opacity and/or refractive indications. SETTING: Instituto de Microcirugía Ocular de Barcelona, Barcelona, Spain. METHODS: This retrospective nonrandomized case series study comprised 44 eyes of 30 consecutive myopic patients who had surgery because of initial lens opacity and/or refractive indications during a 2-year period. In each case, phacoemulsification was performed using an ultrasonic technique and an IOL was implanted in the capsular bag. The patients were seen preoperatively to evaluate retinal pathology. They also had a complete ophthalmologic evaluation that included detailed indirect ophthalmoscopy. All patients were followed at regular intervals. The main outcome measures were preoperative and postoperative spherical equivalent (SE), the incidence of posterior capsule opacification (PCO) and the need for capsulotomy, and the incidence of retinal complications. RESULTS: In all eyes, the surgery was uneventful. The mean patient age at surgery was 42.83 years; the mean preoperative SE was -15.77 diopters (D) and the mean postoperative SE, -1.05 D. No eye required preoperative peripheral retinal photocoagulation. Twenty-five eyes (56.8%) had PCO and had a neodymium:YAG laser capsulotomy. One eye had a retinal tear 14 months after surgery and was treated with focal photocoagulation. The mean endothelial cell loss was 2.1% during the first postoperative year. Two eyes had an immediate postoperative intraocular pressure (IOP) rise, 1 with an inflammatory membrane and the other with corneal edema; both resolved with topical treatment. One eye with elevated IOP and a bad response to medical treatment had argon laser trabeculoplasty. No eye had a retinal detachment during the follow-up. CONCLUSION: With a thorough preoperative ophthalmologic evaluation and uneventful surgery, patients who have phacoemulsification and IOL implantation for the correction of myopia have a satisfactory chance of obtaining good visual results with few complications.     

Retinal angiomatous proliferation responds safely to a double dose (1.0 mg) of ranibizumab

A 77‐year‐old man presented with sudden foggy central vision in the right eye. The visual acuity (VA) was 6/60 (R) and 6/6 (L). Funduscopy revealed superficial macular haemorrhage in the right eye. Using fluorescein angiography and indocyanine green angiography, retinal angiomatous proliferation was confirmed. Two intra‐vitreal injections of bevacizumab were given but the VA did not improve. Following this, he received an intra‐vitreal injection of ranibizumab. Regression of the retinal angiomatous proliferation was observed and the VA of the right eye returned to 6/10. Simultaneously, his left eye suffered from sudden visual loss and retinal angiomatous proliferation was diagnosed. Three intra‐vitreal injections of ranibizumab were given. Regression of the retinal angiomatous proliferation was observed and the VA of the left eye was stabilised. Another 80‐year‐old man complained of sudden distorted vision in his left eye. Funduscopy and optical coherence tomography (OCT) revealed superficial macular haemorrhage and retinal pigment epithelial detachment (RPED). The VA was 6/12 and retinal angiomatous proliferation was diagnosed. He received an intra‐vitreous injection of bevacizumab followed by photodynamic therapy (PDT). The RPED was resolved; however, the VA dropped to 2/60. Optical coherent tomography, fluorescein angiography and indocyanine green angiography were used to indentify retinal angiomatous proliferation. Intra‐vitreal injection(s) of a double dose (1 mg) of ranibizumab is a worthwhile treatment, as it can stabilise and even improve the VA without significant side effects.     

Panretinal photocoagulation aggravates experimental proliferative vitreoretinopathy

The effects of panretinal photocoagulation (PRP) on intravitreal proliferation were evaluated in an experimental model for proliferative vitreoretinopathy (PVR). Thirty-three pigmented rabbits underwent argon laser PRP in one eye. Cultured fibroblasts (2 x 10⁵ or 4 x 10⁵ cells) were implanted into the intact vitreous of both eyes of each animal either 3 days after PRP (when acute laser lesions were present) or 4 weeks after PRP (scarred laser lesions). PVR was assessed by indirect ophthalmoscopy for 4-8 weeks. Histological examination included staining with monoclonal antibodies against glial fibrillary acidic protein (GFAP). In both groups significantly more severe stages of PVR developed after PRP than in the controls. Total retinal detachments ensued in 13 photocoagulated eyes versus five controls. PRP induced invasion of macrophages, proliferation of retinal pigment epithelium and a conspicuous Müller cell response, enhancing intraocular inflammation, which stimulated intravitreal proliferation and aggravated PVR.Presented in part at the annual meeting of the Association for Research in Vision and Ophthalmology, Sarasota, Florida, 2 May 1989     

Fat adherence syndrome after retinal surgery treated with amniotic membrane transplantation

PURPOSE: We present favorable results with amniotic membrane transplantation in a patient who developed fat adherence syndrome after retinal surgery. DESIGN: Interventional case report. METHODS: A 37-year-old man had diplopia resulting from hypotropia of the left eye after retinal detachment surgery. Removal of a previously implanted silicon sponge had little effect because of fibrous adhesion between the inferior rectus muscle and adjacent periorbital fat. We performed amniotic membrane transplantation combined with conventional extraocular muscle surgery. RESULTS: Postoperatively, supraduction of the left eye became almost full. The field of binocular vision was extended markedly by treatment, both in the primary position and with downward gaze. These improvements remained stable over 1 year of follow-up. CONCLUSION: Amniotic membrane transplantation appears to be effective for preventing regrowth of restrictive scar tissue in the fat adherence syndrome.     

Control of experimental massive periretinal proliferation by daunomycin: dose-response relation

A condition similar to massive periretinal proliferation in man can be produced in rabbits by injecting homologous fibroblasts into the vitreous. We have studied the effect of daunomycin, a cytotoxic drug, in this model to determine a dose which would not be toxic to the retina but would be effective in preventing proliferation of the injected fibroblasts and eventual retinal detachment. The results of this study demonstrate that daunomycin at a dose of 9 nmol per eye reduces the incidence of retinal detachment by over 50%. Doses higher than 30 nmol per eye are toxic to the retina.     

Intraocular cilia associated with perforating injury

PURPOSE: To report a case series of penetrating injury complicated by occurrence of intraocular cilia. METHODS: Retrospective analysis of charts of 11 eyes of 11 patients with penetrating injury and intraocular cilia, presenting between September 1978 and November 1998. Ten eyes underwent surgery for trauma-related problems such as cataract, vitritis, retinal detachment etc., at which time intraocular cilia were removed. One eye did not have surgery and continues to harbour cilia at the posterior perforation site. RESULTS: Metallic wire was responsible for injury in 6 of 11 eyes with intraocular cilia. Five eyes had significant intraocular inflammation. The cilia were located in the anterior segment in 4 eyes; in the posterior segment in 6 eyes and in both in one eye. At the last follow up, 72.7% had 6/18 or better vision. Poor vision in the rest was due to recurrent retinal detachment (2 eyes) and macular scarring (1 eye). CONCLUSION: Intraocular cilia are more commonly associated with injury by a metallic wire. The presentation and management of an injured eye does not seem to be influenced by the presence of cilia in the eye.