The retinal depression sign in diabetic retinopathy

Background: The retinal depression sign, an abnormal light reflex due to ischemia-induced focal inner retinal atrophy, was initially described in patients with sickle cell retinopathy. We undertook this study to characterize the finding in diabetic retinopathy. Methods: The fundus photographs of 97 consecutive patients with diabetic retinopathy seen in the Penn State University Ophthalmology Department were reviewed. We recorded age, sex, type of retinopathy, visual acuity and photographic details, including the presence or absence of the retinal depression halo. Results: The retinal depression sign was present in 9 of 22 patients age 45 years or under, versus 1 of 75 patients age 46 or older (P<0.0001, two-tailed Fisher's exact test). The presence or absence of retinal depression sign did not predict the type of retinopathy in a given patient. Eleven (70%) of the affected eyes had visual acuity 20/40. Conclusion: The retinal depression sign is common in younger patients with diabetes and should be distinguished from other macular lesions associated with diabetic retinopathy.     

Isovolemic hemodilution increases retinal tissue oxygen tension

Background: Therapeutic isovolemic hemodilution has been reported to improve blood flow and oxygen delivery. Few reliable measurements have been made, however, showing the effect of hemodilution on tissue oxygen tension. Methods: We measured retinal oxygen tension during experimental isovolemic hemodilution in normal cats. Polarographic oxygen microelectrodes were placed in the vitreous humor within 100–200 m of the retinal surface.Results: Tissue oxygen tension increased initially during isovolemic hemodilution to a maximum approximately 50% above baseline at approximately two thirds of the original hematocrit level. Hemodilution beyond this point to lower hematocrits caused a steady decline in tissue oxygen tension. Cardiac output measured in one cat undergoing isovolemic hemodilution increased as hematocrit was lowered, but the cardiac erythrocyte flux actually decreased steadily.Conclusion: The observed increase in tissue oxygen tension with hemodilution appears to be explained by a lesser reduction in capillary than in systemic hematocrit, coupled with an increased capillary blood flow. The increase in tissue oxygen tension we observed could in part explain the clinically beneficial effects of hemodilution.     

Retinopathy in diabetic hypertensive monkeys: a pathologic study

Background: No satisfactory primate model of diabetic retinopathy has been produced. The clinical picture of microangiopathic retinopathy in diabetic hypertensive monkeys has been previously reported. The present study describes the pathologic findings of these animals. Methods: Eleven eyes of six monkeys (five rhesus, one cynomolgus) were studied. Diabetes mellitus was either spontaneous or induced by streptozocin; mild arterial hypertension was either spontaneous or induced by fludrocortisone acetate. In two monkeys, the horseradish peroxidase tracer technique was employed. Trypsin flat preparations of the nasal retinal vasculature were prepared. The material was studied by light and electron microscopy. Results: We divided the development of the microangiopathic retinopathy into three stages. In the early stage, background retinopathy was characterized by microvascular abnormalities and capillary dropout. Massive vascular leakage, intraretinal exudates and hemorrhage, cystoid degeneration, and cotton-wool spots were features of an exudative retinopathy in the second stage. In the final stage, chronic ischemic retinopathy was characterized by vascular occlusions and areas of retinal atrophy. Conclusion: Microangiopathic retinopathy in diabetic monkeys with mild hypertension presented many features of human diabetic and hypertensive retinopathy, except vitreous neovascularization.     

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.     

Susceptibility of human retinal pigment epithelial cells to different viruses

Background Different viruses have been reported to be involved in retinal diseases in animalsystems. In humans, herpes simplex virus and cytomegalovirus have been found to cause retinal disease. Most of the studied viruses are neurotropic. In this study, the in vitro susceptibility of human retinal pigment epithelial cells (RPEC) to representative members of different groups of human pathogenic viruses was investigated. Methods Early cultures of RPE C — after two or three passages — were infected with the following viruses: herpes simplex virus (HSV) type 1, human herpesvirus 6 (HHV-6), Epstein-Barr virus (EBV), cytomegalovirus (CMV), adenovirus types 1 and 7, measles virus, parainfluenza virus and coxsackie virus B3. Results Cultures of RPE C could be infected with neurotropic viruses like HSV or measles virus as well as with typical respiratory viruses like parainfluenza or adenoviruses. Coxsackievirus, an enterovirus, replicated as well as human CMV whereas EBV and HHV-6, two lymphotropic viruses, failed to infect RPE. Conclusion These findings suggest that a variety of viruses, including those causing rather common illnesses, might be capable of inducing retinal lesions under certain circumstances due to haematogenous spread during the course of viraemia.     

Optic disc morphology in diabetes mellitus

Background: Diabetes mellitus is a systemic disease affecting multiple tissues throughout the body. This study was performed to evaluate intravitally the diabetic changes of the optic disc Methods: Color photographs of 115 eyes with varying severity of diabetic retinopathy and of 29 normal eyes were morphometrically examined Results: We found that the size and shape of the optic disc, the neuroretinal rim and the parapapillary atrophy did not differ significantly between the diabetic eyes and the normal eyes. These variables were independent of the degree of diabetic retinopathy. There was a tendency toward decreased visibility of the retinal nerve fiber layer and increased optic disc pallor in the diabetic eyes Conclusion: The results indicate that the area and form of the optic disc, the neuroretinal rim and parapapillary atrophy are not altered by diabetes mellitus. This is important for the diagnosis of glaucoma in diabetic patients, since glaucoma leads to a decrease of rim area and an enlargement of parapapillary atrophy. The reduced visibility of the retinal nerve fiber layer, the increased optic disc pallor and the unchanged size of the neuroretinal rim and parapapillary atrophy suggest that diabetes mellitus may be associated with nonglaucomatous optic nerve atrophy.     

Morphometry of the optic nerve and retinal vessels in children by computer-assisted image analysis of fundus photographs

Background: The retinal fundus in childhood has a different morphology than in adulthood. Existing methods are not suitable for evaluation of fundus photographs from children. Therefore, a new method for quantitative analysis of fundus morphology utilizing a personal computer-assisted digital mapping system was developed. Methods: A CCD flatbed scanner is used to digitize fundus photographs, producing computer images which are analyzed on an IBM/AT computer. Area measurements of the optic disc, excavation and peripapillary crescent are made, as well as determinations of the length, branching, tortuosity and distribution of the retinal vessels on the fundus surface. Results: Determination of the inter-and intra-observer variability of the computer-assisted image analysis technique demonstrated good reproducibility. The method is demonstrated using fundus photographs of six normal children and six children with the fetal alcohol syndrome. Typical variations in appearance of optic disc and retinal vessels are seen. Conclusion: The system is unique in measuring both the optic nerve head and the retinal vessels and is therefore especially useful for detailed studies of normal and abnormal development of these structures in children.     

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.     

Protective role of excitatory amino acid antagonists in experimental retinal ischemia

Background: Excitatory amino acids and their analogues (NMDA, kainate and AMPA) are implicated in the pathogenesis of ischemic brain injury. In order to fully understand their involvement in the pathogenesis of retinal ischemic injury, we studied the electrophysiological and histopathological effects of two excitatory amino acid antagonists, cis-PDA and MK 801, in an experimental retinal ischemia model. Methods: The two antagonists were injected intravitreously 15 min before ischemia was induced by elevatory intraocular pressure caused by external compression. Electrophysiological and histopathological evaluation was made 48 h after 45 min transient ischemia. Results: The excitatory amino acid antagonists cis-PDA and MK 801 can partially protect against retinal ischemic injury; whereas the mean post-ischemic b-wave amplitude corresponded to 41% of the pre-ischemic value in the control group, it was 64% (P=0.003) and 59% (P=0.005) following administration of cis-PDA and MK 801 respectively. Histopathological study corroborated these data, showing significant differences for morphometric parameters (P=0.011 and P=0.007 respectively). Conclusion: These preliminary results suggest the possibility of limiting excito-toxicity, one of the lesion-forming mechanisms in ischemic retinal injury.     

Effect of oxygen on relaxation of retinal pericytes by sodium nitroprusside

Background: This study addresses whether oxygen modulates the relaxation induced in retinal pericytes by sodium nitroprusside (SNP), a nitric oxide (NO) donor that stimulates the NO/guanylate cyclase pathway. Methods:Bovine retinal pericytes were cultured on silicone. On the silicone surface, basal pericyte contractile tone induces wrinkles. Drug-induced changes in pericyte contractile tone were assessed by changes in the number of wrinkles. The effects of 100% nitrogen (hypoxia) and 100% oxygen (hyperoxia) were studied on: (a) the basal tone of quiescent pericytes, (b) the relaxation to 3 and 10 M SNP or 1 M forskolin, and (c) the recontraction that followed the washout of 3 M SNP or 1 M forskolin. Results: Neither hypoxia nor hyperoxia had any apparent influence on pericyte basal tone, on forskolin-induced relaxation, or on pericyte recontraction after a forskolin-induced relaxation. In hypoxia, relaxations to SNP 3 M (P<0.05) and 10 M (P<0.01) were significantly more pronounced than in hyperoxia. Hypoxia also reduced the recontraction after an SNP-induced relaxation (P<0.001). Conclusion: Oxygen modulates the relaxation of bovine retinal pericytes evoked by SNP (guanylate cyclase-mediated), but not the relaxation induced by forskolin (adenylate cyclase-mediated). These results suggest that in the retinal capillary circulation an interaction between oxygen and the NO/guanylate cyclase pathway modulates pericyte tone, and thus potentially blood flow.     

Anterior segment findings in AIDS patients with cytomegalovirus retinitis

Background: Anterior segment findings in AIDS patients presenting with cytomegalovirus (CMV) retinitis have not been specifically addressed in the American literature. Methods: Our study evaluated 21 AIDS patients with CMV retinitis. Results: Nineteen (90%) of these patients exhibited corneal endothelial deposits concurrent with CMV retinitis. The endothelial deposits were microscopic, opaque, linear flecks arranged in a reticular-like fashion. Of 42 eyes evaluated, 32 (76%) demonstrated active CMV retinitis. Corneal endothelial deposits were noted in 26 (81%) of the 32 eyes with retinitis. These corneal endothelial deposits were absent in the eyes which did not have CMV retinitis. Conclusion: Meticulous examination of the retina of an HIV-positive or AIDS patient who presents with reticularly arranged, linear, flecked corneal endothelial deposits should be performed to ensure that the diagnosis of CMV retinitis can be ruled out.     

Familial exudative vitreoretinopathy: surgical intervention and visual acuity outcomes

Background: Familial exudative vitreoretinopathy (FEVR) is a hereditary condition that may lead to vitreous hemorrhage and traction retinal detachment necessitating surgical intervention. In this paper we review the results of surgery on seven such patients (eight eyes). Methods: Seven patients (eight eyes) were followed up after surgery that had been performed because of vitreous hemorrhage and/or traction retinal detachment due to FEVR, in an effort to evaluate outcomes. Parameters that were noted were the current age, gender, age at the time of first surgery, length of follow-up and postoperative retinal status and visual acuity. Results: Seven patients (eight eyes) ranging in age from 6 months to 44 years with a mean of 24.7 and a median of 26 years were followed. There were three females and four males. The lowest age at which surgery was first performed was 6 months and the highest was 28 years, with a mean of 14.7 and a median of 17 years. Six of the 8 eyes were reattached following surgery, although some required multiple procedures. Conclusion: Vitreoretinal surgery may be of benefit in helping to preserve some degree of vision in eyes of patients with FEVR who develop vitreous hemorrhage and/or retinal detachment.Presented at the combined meeting of the Club Jules Gonin and the Retina Society, 3 September 1996     

Expression of mRNA coding for TNFα, IL-1β and IL-6 by cells infiltrating retinal membranes

Background: Cellular mechanisms of inflammation are thought to be involved in the pathogenesis of proliferative vitreoretinopathy, and cytokines, which are products of cell activation, are known to play an important role in the development and maintainance of inflammatory reactions. It was the aim of this work to investigate the presence of cells expressing cytokine mRNA within retinal membranes. Methods The presence of mRNA coding for the cytokines interleukin 1 (IL-1), interleukin 6 (IL-6) and tumour necrosis factor (TNF) was investigated in 19 epiretinal membranes obtained from eyes undergoing vitrectomy for the treatment of retinal detachment complicated by proliferative vitreoretinopathy. Results Cells expressing mRNA for IL-1 were observed in 7 membranes, cells positive for IL-6 mRNA were seen in 12 membranes, and cells exhibiting mRNA for TNF were present in 9 specimens. Only three membranes contained cells expressing mRNA for all the cytokines investigated. Four membranes possessed positive cells for IL-6 and TNF, two contained cells expressing mRNA for IL-6 and IL-1, and two others exhibited cells expressing mRNA for TNF and IL-1. Five membranes contained IL-6 mRNA-positive cells only, whilst two exhibited cells expressing mRNA for IL-1, or TNF only. Conclusion The present findings indicate that cellular activation may occur during the development of PVR, and suggest that these cytokines may be locally produced by cells infiltrating epiretinal membranes. The presence of IL-1, IL-6 and TNF mRNA-positive cells within retinal membranes provides further evidence of a pathogenic role of these cytokines in proliferative vitreoretinopathy.     

An immunocytochemical study of isolated human retinal Müller tells in culture

Background: We report a modified method for the isolation and propagation of adult human Müller cells in culture. Methods: The retina of postmortem human eyes was mechanically dissociated and cultured. Using immunocytochemical techniques, these cells were stained with monoclonal antibodies specific for Müller cells, glial fibrillary acidic protein (GFAP), vimentin, glutamine synthetase (GS) and keratin. Transmission electron microscopy (TEM) was also performed. Results: The dissociated and cultured cells expressed vimentin and GS, but not GFAP. At least 85% of these cells stained with a Müller tell-specific monoclonal antibody. Using TEM, flat cells containing 13-nm intermediate filaments and glycogen were identified. Conclusion: Human retinal Müller cells tan be isolated and propagated in culture. Purified cell cultures are required for controlled studies of the normal physiology and pathologie responses of Müller cells.     

Visualization of retinal and choroidal blood flow with fluorescein leukocyte angiography in rabbits

Purpose: To visualize the retinal and choroidal leukocytes in rabbits with a new technique, fluorescein leukocyte angiography using a scanning laser ophthalmoscope. Methods: Blood was withdrawn from an ear vein of a rabbit (New Zealand White), mixed with fluorescein dye in a test tube and centrifuged. The yellow-brown coat layer containing fluorescein-stained leukocytes was collected and injected into the ear vein of the same rabbit while performing fluorescein angiography with a scanning laser ophthalmoscope. The angiographic image displaying circulating fluorescent leukocytes in retinal and choroidal vessels was recorded on a videotape. Results: Fluorescent leukocytes were clearly visible in the retinal arteries, capillaries, veins and choroidal vessels for more than 1 h. Plugging of leukocytes was seen throughout this period of time in choroidal vessels, while plugging was rare in retinal vessels. Conclusions: Fluorescein leukocyte angiography is a new technique which can be used for visualization of the leukocytes in retinal and choroidal vessels non-invasively and in vivo.Presented in part at the 5th International Meeting on Scanning Laser Ophthalmoscopy, Tomography, and Microscope, San Antonio, Texas, 26–28 October 1995; Presented as a video presentation at the 76th meeting of the Korean Association of Ophthalmology (Seoul, 15–16 May 1996     

Retinal pigment epithelial cells: autocrine and paracrine stimulation of extracellular matrix contraction

Background: This study was carried out to examine the biological activity of contraction promoters produced by dedifferentiating retinal pigment epithelial cells (RPE) and to evaluate the importance of autocrine and paracrine effects within a semi-closed environment like the vitreal cavity. Methods: RPE at different stages of dedifferentiation in culture were examined for their ability (a) to generate tractional forces in vitro, with and without serum stimulation, and (b) to produce and release contraction-stimulating proteins. Autocrine versus paracrine effects of cell-secreted promoters were tested by using RPE or human dermal fibroblasts (HDF) as target cells. The contraction-stimulating activity of the cell-secreted promoters was partially characterized and compared to the activity of defined promoters. Results: Our study confirmed that RPE can synthesize and secrete cell-contraction-promoting factor(s) active in stimulating the development of tractional forces by RPE as well as HDF. The quantity of biological activity secreted per cell decreases with progressive dedifferentiation, yet the responsiveness of the cell to contraction promoters increases. The contraction promoter(s) synthesized by RPE is partially distinct from the promote rs in serum, TGF-1 and 2, IGF-1, ET-1 and PDGF. The contraction-promoting effects of the RPE product(s) can be completely blocked by staurosporine. Conclusion: Dedifferentiation of RPE is characterized by increasing capacity to generate tractional forces and decreasing synthetic capacity. RPE within a semi-closed system like the vitreal cavity can, theoretically, act both as promoting and active component of traction-related events (tractional retinal detachment).     

Tolerance of human fetal retinal pigment epithelium xenografts in monkey retina

Background: RPE transplantation offers the possibility of treating certain forms of retinal degeneration. Understanding how to optimize the surgical technique for performing RPE transplantation, especially in primates, is therefore of considerable interest. Methods: Fifteen patch RPE transplants were performed in six monkeys. The transplant sites were examined at follow-up by ophthalmoscopy, biomicroscopy, fluorescein angiography and histology. Foveal and peripheral retinal transplants were compared. Results: Human fetal RPE xenografts can survive without rejection for at least 6 months after transplantation in monkey retina. Such grafts form a basal lamina and make intimate contacts with the outer segments of the host. Both rods and cones retain a normal appearance when in contact with unrejected transplants. Rejection occurred in only 30% (3/10) of the peripheral but in 60% (3/5) of the foveal transplants. Conclusions: Cultured human fetal RPE patch transplants can survive and maintain local photoreceptor integrity for relatively long periods of time in monkey subretinal space without immunosuppression. Rejection, when it occurs, is more frequent near the fovea.     

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.     

Ocular findings in Japanese women with nevus of Ota

Background: Nevus of Ota is common in Japanese women, but most patients are not examined ophthalmologically. Methods: We performed ophthalmologic examinations on 16 Japanese women who had had bluish pigmentation in the periorbital region, sclera, and conjunctiva since birth. Results: Fifteen patients had unilateral involvement, and one had bilateral lesions. The visual acuities were good, and the intraocular pressures were within normal range. All patients had a negative family history. Three patients had light pigmentation in the optic disc in the affected eye. Conclusion: We believe that optic disc pigmentation associated with nevus of Ota, as found in these three patients, may be common but have been rarely described.     

How often do patients need visual field tests?

Background: This study was undertaken to determine whether the interval between visual field tests affects the ability to detect progres sive glaucomatous field loss. Methods: One hundred and nineteen retinal locations which were deteriorating significantly by 1 dB/year (untreated normal tension glaucoma patients: 6 eyes) were studied. Analysis was repeated using thinned visual field tests: one test per year instead of the complete three per year over a period of 4 years. Results: The thinned tests identified only 45.4% of the deteriorating points over the 4-year period. Furthermore, there was a mean delay of 1.10 years in detection (P<0.01). Conclusions: Less frequent visual field testing detects fewer progressing locations and detects them later.Presented in part at the Association for Research in Vision and Ophthalmology Annual Meeting, May 1995 and at the American Academy of Ophthalmology Meeting, October 1995.The authors have no proprietary interest in any of the materials used in this study.