Evidence of cross-link formation of vitreous collagen during experimental ocular inflammation

Purpose: To determine the mechanisms of vitreous changes during ocular inflammation. Methods: We investigated vitreous changes, with special emphasis on collagen, in an experimental model of ocular inflammation induced by intravitreal injection of endotoxin (Escherichia coli) in rabbits. Results: Inflammation caused gel contraction and loss of elasticity, accompanied by release of a water-like liquid from the gel, and increases in the amount of insoluble material and highmolecular-weight components of vitreous collagen, presumably due to extensive cross-links of the collagen molecules. Those changes were partially inhibited by intravitreal injection of superoxide dismutase. Conclusions: The crosslinks of vitreous collagen may promote vitreous gel contraction and release of a water-like liquid from the gel. Superoxide anion may play a role in this process.     

The effect of nasolacrimal occlusion on drug-induced mydriasis

Background: Nasolacrimal occlusion has been shown to improve the efficacy of some topically applied ocular drugs. The aim of this study was to investigate the effect of nasolacrimal occlusion on tropicamide-induced mydriasis. Methods: We compared pupillary dilatation by 0.125% tropicamide with and without nasolacrimal occlusion in 40 healthy volunteers. Results: Analysis of variance with repeated measures failed to show any advantage due to nasolacrimal occlusion in drug-induced mydriasis. Conclusion: Nasolacrimal occlusion did not increase the mydriasis obtained with 0.125% tropicamide.     

Intracorneal bovine albumin: an immunologic model of corneal angiogenesis

Background: We characterized the neovascularization that follows the intracorneal injection of bovine albumin (BA) in rabbits as a model of corneal angiogenesis. Methods: New Zealand white rabbits received intracorneal injections of phosphate-buffered saline with and without various amounts of BA. The rabbits were co-sensitized or presensitized by intramuscular BA or were not sensitized. The corneal vascular response was quantified by ranking photographs taken periodically after the injection. Results: In pre-sensitized animals, blood vessels were apparent within 4 days and reached maximum intensity 14 days after the intracorneal injection. Corneas also vascularized in nonsensitized rabbits, but a larger dose (>0.2 mg BA) was required than in pre-sensitized animals (>0.02 mg BA). Vascularization began later in non-sensitized animals and was less extensive than in pre-sensitized animals. Conclusion: The intracorneal injection of BA is a reproducible model of corneal angiogenesis in rabbits and should allow the involved immunological mechanisms to be elucidated.     

Endophthalmitis after Lasiodiplodia theobromae corneal abscess

Background:Lasiodiplodia theobromae is an exceptional cause of human keratomycosis. Patient: We treated a 53-year-old man with fungal keratitis, which had been treated with topical betamethasone and gentamicin for 1 month, and endophthalmitis due toLasiodiplodia theobromae. Despite intensive systemic, topical and intravitreal fungicidal treatment, enucleation had to be performed. Results: The vitreous aspirate cultures were negative as of the second amphotericin intravitreal injection. However, histology revealed that the fungus was present in the cornea, ciliary body, iris and retina. Conclusion: The use of topical steroids may worsen the outcome of the infection.     

Hemoglobin exacerbates the ocular inflammatory response to endotoxin

Background: There is a clinical impression that bleeding into sites of inflammation exacerbates the inflammatory response. It has been hypothesized that hemoglobinic iron (Fe) contributes to this response by catalyzing free radical reactions. In the present study, the effects of autologous hemoglobin on the inflammatory response to endotoxin was determined. In addition, the possible contributions of Fe to this response was assessed by co-injection of either transferrin or desferrioxamine. Methods: A mild ocular inflammation was induced in rabbits by intravitreal injection of 0.25 ng endotoxin. In some animals apotransferrin, hemoglobin, hemoglobin + apotransferrin or hemoglobin + desferrioxamine were co-injected. Twenty-four hours later, anterior uveitis was quantified by slit-lamp examination and determination of protein concentration and infiltration of white cells into the aqueous humor. Results: Co-injection of autologous hemoglobin with endotoxin greatly exacerbated the ocular inflammatory response to endotoxin, especially the infiltration of white cells, which was increased 15-fold. Both apotransferrin, which binds Fe at high affinity, and desferrioxamine, which chelates Fe, greatly decreased the cellular response to the co-injection. Conclusions: It is likely that hemoglobinic Fe is responsible for the increased infiltration of white cells caused by the co-injection of autologous hemaglobin and endotoxin.     

Ophthalmological and neuro-ophthalmological involvement in Churg-Strauss syndrome: a case report

Background: It is well known that different types of eye involvement may develop during the course of systemic vasculitides. Methods: We report here a case of Churg-Strauss syndrome (allergic granulomatous angiitis) characterized by the presence of multiple ophthalmological and neuro-ophthalmological lesions, i.e., mononeuritis of the fourth cranial nerve, multifocal choroidal ischaemia, and bilateral ischaemic optic neuropathy. Results: Ischaemic lesions in the posterior ciliary plexus and chorio-retinal circulation, which appeared simultaneously after a phase of disease activity, were documented. Conclusion: The simultaneous occurrence of multiple ocular features in a patient with Churg-Strauss syndrome suggests that regional vasculitis may be the pathological mechanism underlying the multiple ophthalmological lesions in this disorder.     

HLA antigens in a Japanese family with Behçet's disease

Background: Familial Behçet's disease is rare. Methods: HLA antigens in a Japanese family with Behçet's disease were examined. Results: The affected patients had HLA B51, and unaffected family members also had the same antigen. Conclusion: It is likely that not only HLA B51 but also other factors may be involved in the pathogenesis of Behçet's disease in Japanese patients.     

Angiogenesis in early choroidal neovascularization secondary to age-related macular degeneration

Background: The morphological features of angiogenesis in early choroidal neovascularization secondary to age-related macular degeneration are yet to be fully described. Methods: Six eyes from five patients which on clinical and histological examination showed advanced age-related macular degeneration and early choroidal neovascularization have been studied by transmission electron microscopy. Results: Pre-existing choroidal capillaries and venules showed changes which included endothelial cell budding, pericyte enlargement, endothelial cell sprout formation and the development of intrachoroidal new vessels. In one case, an endothelial cell sprout continuous with an intrachoroidal vessel penetrated Bruch's membrane. Examination of early subretinal pigment epithelial new vessels showed them to spread between the inner layers of Bruch's membrane within the space usually occupied by the basal linear deposit and drusen. New vessel formation took place in blind pouches at the margins of new vessel networks, either in the absence of pericytes or in the presence of mainly myofibroblast-like pericytes. Conclusion: This ultrastructural study describes two phases of new vessel growth associated with the onset of choroidal neovascularization secondary to age-related macular degeneration. The initial intrachoroidal phase appears to be a low-turnover form of neovascularization which may lead to new vessels penetrating Bruch's membrane. Extensive subretinal pigment epithelial neovascularization, on the other hand, results from a high-turnover phase of neovascularization characterized by extensive endothelial cell proliferation and migration. Pericyte phenotypic changes associated with these different phases of neovascularization appear to relate to the dynamics of angiogenesis taking place in each process.     

Magnetic resonance imaging of cyclodialysis clefts

Background: Our purpose was to determine whether cyclodialysis clefts can be imaged with magnetic resonance imaging (MRI). Methods: Surgical cyclodialysis clefts extending approximately 3 clock hours were created in four New Zealand white rabbits. Eyes were scanned with an ocular MRI coil. Images obtained after intravenous gadolinium, topical godalinium, and gadolinium injected into the cleft were compared to images obtained without contrast. Two human eyes were also scanned for cyclodialysis clefts with MRI. Results: Direct injection of gadolinium into the suprachoroid space yielded definitive localization and delineation of the cyclodialysis cleft. Cyclodialysis clefts could also be imaged following enhancement with topical or intravenous gadolinium. Without contrast medium, the clefts could not be clearly identified in rabbits. In a patient with hypotony and choroidal effusion following cataract surgery, a cyclodialysis cleft and enhancement of the suprachoroidal space were found with intravenous administration of gadolinium. MRI from a patient with a trabeculo-suprachoroidal shunt also demonstrated gadolinium enhancement of the suprachoroidal space. Conclusion: Cyclodialysis clefts can be imaged using gadolinium-enhanced MRI in rabbits and humans.The authors have no proprietary interest in the companies or products mentioned in this articlePresented in part at the Annual Meeting of the Association for Research in Vision and Ophthalmology, Sarasota, Fla. 15 May 1995     

Orbital exenteration: Surgical and reconstructive strategies

Background: Radical exenteration procedures, which include the removal of orbital content and eyelids, result in serious functional limitations, especially with respect to eating and speaking. Therefore we have recently changed our surgical concept. Methods: Seventy-seven patients underwent orbital exenteration during the 20-year period from 1974 to 1995 at the Department of Maxillofacial Surgery, Essen University. The simultaneous removal of periorbital bone was performed in 45 of these cases. Results: The 1-year survival rate was 89%, the 5-year rate was 63% and the 10-year rate was 48%. The surgical approach, the amount of resected orbital tissue and the reconstructive procedure have been adapted to the individual needs, depending on the location and extent of the tumor. Subsequently, the surgical morbidity has decreased. Discussion: Detailed consideration of all clinical and histological findings is essential before surgery, in order to prevent a higher rate of recurrence following these modified operations.     

Unusual retinal pigment epitheliopathy and choroidopathy in carcinomatosis: A rare case of cancer-associated retinopathy

Background: Cancer-associated retinopathy is a syndrome causing ocular symptoms. It is a rare entity and only a few cases have been reported. Methods: A 67-year-old woman with small-cell endometrial carcinoma suffering from deterioration of visual acuity is presented. Results: The patient presented with extensive mottled changes of the retinal pigment epithelium, accompanied by diffuse subretinal fluid in the posterior pole and exudative retinal detachments inferior in both eyes. Conclusion: This patient suffered from a rare variety of cancer-associated retinopathy.     

Collagen synthesis in lens epithelial cells on capsules containing intraocular lens implants in rabbits: immunolocalization of prolyl 4-hydroxylase

Background: We evaluated ultrastructurally the presence and distribution of lens epithelial cells and extracellular matrix on the posterior capsule after implantation of a silicone or a polymethylmethacrylate (PMMA) intraocular lens (IOL) in rabbits. The immunolocalization of prolyl 4-hydroxylase, an enzyme involved in procollagen synthesis, was also examined in such cells. Methods: Anesthetized adult albino rabbits (n=12) underwent phacoemulsification and aspiration (PEA) of the crystalline lens and implantation of a silicone or a PMMA IOL into the capsular bag of one eye. They were killed by an intravenous overdose of pentobarbital sodium. The lens capsules were processed for transmission electron microscopy and for immunohistochemical detection of the -subunit of prolyl 4-hydroxylase. Results: Ultrastructurally, lens epithelial cells on the posterior capsule evidenced an accumulation of collagenous extracellular matrix. Prolyl 4-hydroxylase immunoreactivity was detected in the cytoplasm of cells distributed on the capsules. Conclusion: Lens epithelial cells are involved in the production of collagenous matrix on lens capsules after PEA and implantation of IOL, resulting in a fibrotic process of the lens capsule.     

β-Galactosidase transgene expression in transplanted rabbit retinal pigment epithelial cells in vivo

Background: Intraocular transplantation of genetically modified cells that release a particular substance could have a major impact on the treatment of various ocular diseases. We studied the expression of the reporter gene -galactosidase (lacZ) in transplanted retinal pigment epithelial (RPE) cells in vivo Methods: RPE cells from pigmented rabbits were transduced with the -galactosidase gene in a retroviral vector. Cells were then assayed for gene expression and transplanted subretinally into the eyes of New Zealand White rabbits. RPE cells that were transduced with a similar vector without the -galactosidase gene were used as controls. Rabbits were killed on days 1, 7, and 21 and the eyes processed for transmission electron microscopy Results: Neomycin-resistant rabbit RPE cells that showed -galactosidase activity were generated within 2–5 weeks. After transplantation, viable RPE cells that expressed the transgene and that phagocytosed rod outer segments were observed on days 1, 7, and 21 Conclusions: The results show that generation of genetically modified RPE cells is feasible and that the transplanted cells remain viable and continue to express the transgene in the subretinal space of the host animal for at least 21 days. Transplantation of such genetically modified RPE cells could provide a new tool for studying retinal diseases and, potentially, for correcting metabolic abnormalities in retinal degenerations and dystrophies.     

Pressure sore in a patient who underwent repair of a retinal tear with gas injection

Purpose: To demonstrate a pressure sore following strict head positioning in a patient who underwent encircling band, vitrectomy and gas injection. Methods: A male patient was admitted to the hospital with a large posterior horseshoe tear in the inferior temporal retina with severe vitreous traction and retinal detachment. Encircling band, vitrectomy cryotherapy and gas injection was performed. After surgery the patient was instructed to sit in a facedown position. Results: A pressure sore resulted from prolonged immobility of the right elbow due to face-down positioning following encircling band, vitrectomy and gas injection. Conclusion: A patient injection. Conclusion: A patient may rarely have compulsive personality traits that result in extreme compliance to the physician's recommendations; therefore, general instructions given for head positioning should include permission for a change in position when required, at least for brief periods of time.     

A comparison of colour Doppler imaging of orbital vessels and other methods of blood flow assessment

Background: Comparison of the haemodynamic measurements obtained by colour Doppler imaging and other methods of ocular blood flow measurements was desired. Methods: The blood velocity findings from colour Doppler imaging of patients with central retinal vein occlusion were compared to the results of fluorescein video-angiography, continuous tonography and ophthalmodynamometry. Results: Patients with low or undetectable blood velocities in the central retinal vein had longer retinal dye transit times on fluorescein video-angiography. Tonography showed a positive correlation with the velocities in the ophthalmic artery, but ophthalmo-dynamometry showed a negative correlation with these velocities. Conclusion: The relationships between the blood velocities in orbital vessels and other blood flow measurements emphasise that there is a complex interaction of the blood flow parameters. Care must therefore be taken when interpreting the results of studies.     

Cellular fibronectin and tenascin in experimental perforating scleral wounds with incarceration of the vitreous

Background: Posterior perforating eye injury carries a high risk of visual loss due to the formation of intravireal and epiretinal scar tissue. Intraocular scar formation in patients with retinal detachment has been shown to be associated with elevated intravitreal FN levels. The extracellular matrix glycoproteins fibronectiu (FN) and tenascin (TN) have been located in epiretinal scar membranes. As both FN and TN are also involved in healing of cutaneous and corneal wounds, we undertook to study their expression in rabbit perforating scleral wounds with vitreous incarceration. Methods: A perforating scleral wound was produced and sutured without removal of vitreous from the wound in 18 pigmented rabbits. The rabbits were killed at various times (1 h to 21 days) after the operation, and the indirect immunohistochemical method was used for demonstration of FN and TN. Monoclonal mouse hybridoma antibodies 52 DH1 and 100 EB2, recognizing the cellular form of FN (cFN) and TN, respectively, were used. Results: During the first post-operative week immunoreaction for glycoproteins, both the locally produced cFN and TN, were observed at the scar tissue containing the prolabed vitreous and the adjacent sclera. Subsequently, the reaction gradually shifted to the vitreal side of the wound, and 3 weeks after the operation it was almost completely restricted to a separated mass of vitreous beneath the scar. Conclusion: The expression of cFN and TN in the scleral scar and vitreous is indicative of their local synthesis. The shift of the expression of those proteins to the vitreal side of the wound with time suggests that the scarring process in the vitreous is delayed compared to the sclera.     

Reattachment to a substrate prevents apoptosis of human retinal pigment epithelium

Background: Epithelial cells generally fail to survive in suspension. Harvesting human retinal pigment epithelium (RPE) for transplantation may separate the cells from their extracellular matrix and induce apoptosis. We investigated whether reattachment of RPE to a substrate will prevent apoptosis. Methods: Second-passage human RPE cells were plated onto tissue culture plastic precoated with extracellular matrix, fibronectin or laminin, uncoated tissue culture plastic, untreated plastic and untreated plastic coated with 4% agarose. Reattachment rates were determined for each substrate 24 h after plating. The TUNEL technique was used to determine apoptosis rates in attached cells, unattached cells and the entire cell population. Results: Attachment rates were as follows: ECM-coated tissue culture plastic fibronectin-coated tissue culture plastic laminin-coated tissue culture plastic uncoated tissue culture plastic untreated plastic agarose-coated untreated plastic. Apoptosis rates for the entire cell population increased as the RPE cell attachment rate decreased. The proportion of apoptotic cells in the entire population was inversely related to the percent attached cells (r = -0.95). Conclusion: Reattachment of harvested RPE to a substrate decreased the rate of RPE apoptosisin vitro. RPE cells which are removed from their substrate prior to transplantation must reattach rapidly to a substrate to prevent apoptosis.Presented in part at the Annual Meeting of the Association for Research in Vision and Ophthalmology, Fort Lauderdale, Florida, May 1996     

Retinal toxicity and ocular kinetics of 1-β-D-arabinofuranosyl-E-5-(2-bromovinyl)uracil in rabbits

The intraocular penetration of 1--d-arabinofuranosyl-E-5-(2-bromovinyl)uracil (BV-araU), a new antiviral drug, after oral administration, the effects of non-toxic intravitreal doses of BV-araU, and the intraocular kinetics of BV-araU after intraocular injection were studied in rabbits. The intravitreal penetration of BV-araU after oral administration was very poor: 0.11 ± 0.13 g/ml and 0.20 ±0.02 g/ml respectively in albino and pigmented rabbits 2 h after 30 mg/kg. An intravitreal injection of 200 g BV-araU caused transient electroretinographic (ERG) changes, whereas a 100-g injection and intravitreal irrigation with 20 g/ml BV-araU caused no ERG and histologic changes over the 4-week follow-up period. The half-life of the intravitreal concentration of BV-araU after an intravitreal injection was short (2.4 h). The results suggest that an intravitreal injection of 100 g BV-araU or an intravitreal irrigating solution containing 20 g/ml BV-araU is nontoxic to the retina and may be used for treatment of retinitis caused by varicella-zoster virus or herpes simplex virus type 1.     

Interpretation of high-pass resolution perimetry with a probability plot

Background: The interpretation of high-pass resolution perimetry (HRP) fields can be difficult. An age-related probability plot was derived from a known data base to determine whether this improved specificity and sensitivity in early glaucoma detection Methods: Forty glaucoma patients with minor field loss and 40 normals of equivalent age and sex underwent HRP. All had previous Humphrey field data available for comparison. The detection of previously confirmed field defects by HRP was examined using different parameters. Results: Using the age-corrected 95% confidence levels gave the best results, with sensitivity of 82.5% (33/40) and specificity of 85% (34/40). Using the contour plot yielded lower sensitivity (67.5%), while subjectively eyeballing the ring printout gave higher sensitivity (90%), but led to poor specificity (72.5%). Conclusion: The use of a probability plot enhances the performance of HRP. A certain proportion of cases may be missed using one criterion alone, but combining the information with other indices can increase the yield.The authors have no proprietary interest in the equipment and technique described herein     

Production of neocollagen by cells invading hydrogel sponges implanted in the rabbit cornea

Background Poly(2-hydroxyethyl methacrylate) sponges are artificial tissue-equivalent matrices with potential value as materials for the peripheral zone of artificial corneas. A keratoprosthetic device was developed incorporating a poly(HEMA) spongy skirt which allowed cellular invasion. The present in vivo study investigated the biosynthetic activity of stromal fibroblasts growing within a poly(HEMA) sponge implanted into the rabbit cornea. Methods A porous poly(HEMA) hydrogel was synthesized by polymerization in a large excess of water. Specimens with a pore size larger than 10 m were impregnated with collagen type I and then implanted into the limbal region of cornea in four rabbits. The animals were followed clinically for 28 days, when they were anaesthetized and new sponge specimens were implanted in their second eye. After 2 h, both eyes were enucleated. The 28-day and 2h explants were subjected to autoradiographic analysis following labelling with tritiated proline and to an immunostaining technique using antibodies to collagen types I–VI. Results The autoradiographic analysis showed that the fibroblasts within the 28-day explants continued to be synthetically active and deposited proteins. Using the immunostaining technique, the deposition was most clearly demonstrated by the localization of collagen type III in the tissue invading the sponge. Both techniques failed to indicate any cellular activity in the short-time implants. Conclusions The presence of collagen type III is consistent with a normal healing response of the stromal fibroblasts and indicates that poly(HEMA) sponges are able to function as tissue-equivalent matrices.