Retinal and choroidal responses to panretinal photocoagulation: an ultrastructural perspective

Background: There have been few histological or ultrastructural studies of the outer retina and choriocapillaris following panretinal photocoagulation therapy. This investigation examines the long-term morphological effects of panretinal photocoagulation in two patients with type II diabetes who had received laser treatment more than 6 months prior to death. Methods: Regions of retina and choroid from each patient were fixed in 2.5% glutaraldehyde, dissected out and examined using light microscopy and scanning and transmission electron microscopy. Results: After removing the neural retina, scanning electron microscopy of non-photocoagulated areas of the eye cups revealed normal cobblestone-like retinal pigment epithelial (RPE) cells. Regions with laser scars showed little RPE infiltration into the scar area, although large rounded cells often appeared in isolation within these areas. Sections of the retina and choroid in burn regions showed a complete absence of the outer nuclear layer and photoreceptor cells, with the inner retinal layers lying in close apposition to Bruch's membrane. Non-photocoagulated regions of the retina and choroid appeared normal in terms of both cell number and cell distribution. The RPE layer was absent within burn scars but many RPE-like cells appeared markedly hypertrophic at the edges of these regions. Bruch's membrane always remained intact, although the underlying choriocapillaris was clearly disrupted at the point of photocoagulation burns, appearing largely fibrosed and non-perfused. Occasional choroidal capillaries occurring in this region were typically small in profile and had plump non-fenestrated endothelium. Conclusions: This study outlines retinal and choroidal cell responses to panretinal photocoagulation in diabetic patients and demonstrates an apparent reduction in the capacity of these tissues to repair laser damage.     

The use of tissue plasminogen activator in post-traumatic total hyphaema

Background: We wanted to evaluate whether intracameral injection of tissue plasminogen activator (tPA) is useful in managing traumatic hyphaema. Methods: Two eyes with total hyphaema after a severe penetrating injury were treated with a single intracameral injection of 25 g of tPA 5 and 14 days after the injury, respectively. Results: Most of the blood coagulum dissolved within 24 h, and in one of the two eyes the intraocular pressure decreased from 45 to 8 mmHg. The other eye was hypotonic. No re-bleeding or complications related to the use of tPA were noticed. Conclusion: The results in these two cases suggest that tPA is a useful adjunct in managing total hyphaema.     

Scanning laser ophthalmoscope imaging of fluorescein-labelled blood cells

Purpose: To demonstrate the feasibility of a technique for the visualization by scanning laser ophthalmoscope (SLO) of fluores cein-labelled autologous leukocytes and platelets in retinal vessels. Method: Individual blood samples from rats and rabbits were centrifuged to isolate platelets and leukocytes, then passively labelled with fluorescein and reinjected into the same animal. An SLO was used to visualize and record cell displacement in the retinal circulation. Labelled platelets were analysed by flow cytometry. Results: By SLO, platelets appeared as a heterogeneous particle flow, and individual leukocytes appearing as brighter spots could easily be traced. Flow cytometry showed that after labelling platelets were well individualized and their size was slightly increased. Conclusion: Circulating blood cells can be visualized in retinal vessels by a simple method consisting of passive labelling of autologous platelets and leukocytes by fluorescein. No platelet toxicity was detected. This method could be applied to the study of blood cell movement in human retinal vascular diseases.Proprietary interest category: N     

Efficacy of argon laser trabeculoplasty: 3-year preliminary results of a prospective placebo-controlled study

Background: It was the purpose of this study to evaluate the efficacy of argon laser trabeculoplasty (ALT) in controlling intraocular pressure (IOP) and avoiding surgical intervention. We also investigated whether topically applied diclofenac sodium eye drops had an influence on the success rate of ALT compared with placebo eye drops. Methods: The indication for ALT was progressive glaucoma uncontrolled by maximal tolerated medical therapy. Thirty-nine of 41 patients were available for follow-up after 1122±239 days. Results: Twenty-one of 39 eyes failed during the first 3 years of follow-up for one or more reasons: 11 eyes required additional laser treatment and/or filtration surgery because of progressive visual field loss or unacceptably high IOP, 9 eyes failed to have a final IOP 21 mmHg, and 7 eyes failed because of an increase in the number of the medications. This yields a success rate for ALT of 46% for 3-year follow-up. There was no significant difference between diclofenac sodium- and placebotreated eyes concerning the success rate after 3 years (P>0.05). Conclusion: We conclude that the use of ALT for the treatment of glaucoma is best reserved for cases in which medical avenues of treatment have been exhausted.     

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.     

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.     

The ultrastructure of parapapillary chorioretinal atrophy in eyes with secondary angle closure glaucoma

Background: The present study was performed to investigate the ultrastructure of deep retinal layers and choroid corresponding to the parapapillary chorioretinal atrophy in eyes with secondary angle-closure glaucoma. Methods: The glaucomatous eyes included two eyes enucleated due to iris ring melanoma with high intraocular pressure and one eye with neovascular glaucoma enucleated due to ocular pain. The control eyes included one eye enucleated due to choroidal malignant melanoma with normal intraocular pressure and one eye enucleated during surgery for supramandibular carcinoma. These eyes were studied with light and electron microscopy. Results: In the region of parapapillary chorioretinal atrophy of glaucomatous eyes, the retinal pigment epithelial cells showed degenerative changes, such as loss of basal in foldings and microvilli, degenerated mitochondria, vacuolar degeneration and irregular distribution of melanin granules. The photoreceptors were decreased in number in this area of glaucomatous eyes. The lumen of the choriocapillary vessels adjacent to the optic nerve was collapsed. Conclusion: These results elucidate the fine structures of deep retina and choroid in the region of parapapillary chorioretinal atrophy of glaucomatous eyes, and suggest that the reduced choroidal perfusion might be the pathogenetic mechanism of glaucomatous parapapillary chorioretinal atrophy.     

Employment of bioluminescence for the quantification of adenosine phosphates in the human cornea

Background: Quantification of adenosine phosphates in human corneal extracts has been performed using spectrophotometry. We employed the bioluminescence technique to obtain a more sensitive assay for adenosine phosphates and to reduce the volume of the test sample. Methods: The bioluminescence assay for ATP, already known from sterility control, was modified and expanded. Standard curves were established using a standard solution with equimolar concentrations of ATP, ADP and AMP. To monitor the method, adenosine phosphates were measured in 35 human corneal extracts using both spectrophometry and bioluminescence. Results: Linear standard curves ranging from 1 to 45 pmol were established. The two methods yielded comparable results despite the use of a basic dilution of 1: 100 for the new technique. Conclusion: Bioluminescence provides a highly sensitive quantification of adenosine phosphates in the human cornea and facilitates an extremely detailed evaluation of the metabolic status of the cornea.Dedicated to Prof. Martin Reim on the occasion of his 65th birthday     

Corneal neovascularization in rats as a model for photothrombotic therapy using bacteriochlorin a and an argon laser

Background: The presence of vessels has a negative influence on corneal transplant survival. Closure of such vessels prior to transplantation may improve the transplant results, and this might be achieved by irradiating the vessels with argon laser light after intravenous administration of a photosensitizer, e.g. bacteriochlorin a (BCA). A suture-induced corneal neovascularization model in rats was set up to test this hypothesis. Methods: Suture-induced vessels in the cornea of male Wistar rats were irradiated with argon laser light after intravenous administration of BCA. We applied irradiation of varying energy levels and duration and assessed the changes in the vessels by slit-lamp examination, fluorescein angiography and histology. Results: Suture-induced corneal vessels in the rat could be used effectively to study photothrombosis therapy. Intravenous administration of BCA prior to irradiation (=514.5 nm) of the corneal vessels led to vessel closure at lower energy levels and of longer duration than occurred with laser treatment alone. Conclusion: Suture-induced corneal neovascularization in the rat can be used as a model to study the efficacy of photothrombosis therapy. BCA can be used to enhance the rate and duration of vessel closure.     

Cell death and disposal in retinoblastoma: an electron microscopic study

Background: Tumor necrosis and cell death are common features of retinoblastoma. In non-malignant retinal cells after ischemia, as well as in many nonretinal tumors, cell death occurs in at least two ways. We investigated whether similar patterns of cell death could be demonstrated in retinoblastoma cells. Methods: Nine globes with retinoblastoma from eight patients were studied. Paraffin sections stained with HE or the Feulgen method were examined by light microscopy. Several samples from each tumor were selected for electron microscopic study. Results: Ultrastructurally, two main types of cell death were identified. Type I was characterized by progressive lysis of the cytoplasm and karyoplasm. Nuclear chromatin either dissolved or was transformed into compact clumps becoming extracellular dense bodies. Phagocytosis of cell remnants by neighboring tumor cells, or occasional macrophages, was common. Type II was characterized by progressive condensation and shrinkage of the cytoplasm and nucleus. Type II was subdivided in two forms distinguished mainly by characteristic patchy vs crescentic chromatin condensation. Small parts of condensed cytoplasm were engulfed by neighboring tumor cells. Compact cell remnants then underwent either phagocytosis by neighboring retinoblastoma cells or progressive intercellular disaggregation. Conclusion: Retinoblastoma cells may undergo at least two types of cell death. Type I fits the definition of necrosis, while both forms of type II exhibited several features consistent with apoptosis. The types of cell death observed in retinoblastoma exhibited similarities to patterns observed in ischemic retina, as well as in other malignant tumors. Type II cell death (apoptosis) may play a role in limiting tumor growth.Presented in part at the 1993 ARVO Meeting in Sarasota, Fla., USA     

Retinal neovascularization in a case of macular branch retinal vein occlusion

Background. Retinal neovascularization (RNV) has never been described in cases of macular branch retinal vein occlusion (MBRVO), due to the limited amount of ischemia in this form of retinal vein occlusion. Ischemic areas as wide as 5–10disc diameters were required by previous studies to count as ischemic cases of central or major branch retinal vein occlusion. Case report. A 56-year-old woman who had been suffering from MBRVO for 3 years presented at the posterior pole a zone of non-perfusion, extending over 7.5disc areas, and three small tufts of RNV. RNV regressed after two subsequent laser treatments of the ischemia. Retrohyaloid hemorrhage was observed 2 months after the first treatment. Conclusion. Since the average diameter of the non-perfused area was about 2.75disc diameters, this case demonstrates that small RNVs can appear in less extensive areas of ischemia than is generally believed.     

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.     

Cytochemical localization of guanylate cyclase in photoreceptor cells of the mouse

Background: Light-stimulated excitation causes a decrease of the cGMP concentration in vertebrate photoreceptor cells. The cGMP content is restored by the catalytic action of a guanylate cyclase (EC 4.6.1.2). Methods: The spatial distribution of guanylate cyclase was determined cytochemically in rod visual cells of the mouse. Results: In retinal tissue of the mouse guanylate cyclase was found throughout the photoreceptor cells, in the outer and the inner segments, and was especially prominent in the cilia and in elongations of cilia extending into the outer segments. A reaction product of adenylate cyclase (EC 4.6.1.1) could not be demonstrated in vertebrate rod outer segments. Conclusion: The relatively high amount of guanylate cyclase in the inner segments and the cilia may contribute — at least in part — to the actual concentration and the time course of concentration changes of the cGMP concentration in rod outer segments.     

Blood-retina barrier in acute retinal branch vein occlusion

Background: Extensive clinical studies on retinal branch vein occlusion have not yet been able to clarify its pathogenesis. A study designed to look at the associated blood-retina barrier changes may contribute to a better understanding of the different forms of evolution of this pathology. Methods: A prospective study was done in seven patients with recent large temporal branch vein occlusion. Vitreous fluorophotometry, fluorescein angiography and retinal colour photography were performed within the 1st week after the onset of symptoms, 1 week later, and at 12 and 24 weeks. Results: A more marked blood-retina barrier breakdown was found at 1, 2, 12 and 24 weeks in the eyes that later developed extensive capillary non-perfusion. Conclusions: Our results suggest that the breakdown of the blood-retina barrier may play an important role in the subsequent development of retinal nonperfusion in eyes with large branch vein occlusion. We postulate that the eyes that will present later extensive capillary nonperfusion develop, from the initial stages of the disease, a progressive ischaemic capillaropathy characterized by blood-retina barrier breakdown. Retinal pigment epithelium degeneration and arterial lumen narrowing, secondary to the vein obstruction, may help to increase and perpetuate the blood-retina barrier breakdown during the first 6 months after the occlusion.     

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.     

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.     

Ocular blood flow velocity reduction after buckling surgery

Background: It has been reported that scleral buckling reduces the blood flow velocity in retinal vessels. Blood flow changes may also appear in other ocular and extraocular vessels. This study describes the blood flow velocity changes in the ophthalmic artery (OA) after performing this procedure. Methods: The study was carried out in 12 patients (12 eyes) with rhegmatogenous retinal detachment. Color Doppler imaging was used to measure the peak and average blood flow velocity in the OA. Measurements were taken 1 day before and 2 days after scleral buckling surgery was performed. Intraocular pressure (10P) was measured prior to each ultrasound study. Results: We found that statistically significant reductions in the peak flow velocity (33%) and average flow velocity (31%) occur in the OA after scleral buckling. All patients showed an increase in IOP after surgery. Conclusion: Buckling surgery reduces the blood flow velocity in the OA. Since the OA is the origin of the arterial branches that supply blood to the eye, our results suggest that scleral buckling may decrease not only retinal but also choroidal blood perfusion. Some extraocular structures might also be affected.     

Surgical risk factors for severe postoperative proliferative vitreoretinopathy (PVR) in retinal detachment with grade B PVR

Background: Previous studies have shown that grade B proliferative vitreoretinopathy (PVR) is a considerable risk factor for the development of severe postoperative PVR. We conducted a prospective study to elucidate which surgical procedures used in retinal detachment management may stimulate the PVR process in such eyes. Materials and methods: The study included 156 eyes of 152 consecutive patients with rhegmatogenous retinal detachment complicated by grade B PVR referred before any failed surgery and operated on between 1983 and 1993. The parameters evaluated by multivariate statistical analysis included the cumulative circumferential extent of the retinal tears, the extent of the scleral buckle, gas injection, vitrectomy, the method used for retinopexy, and the time of surgical management during the period of the study. Results: The incidence of severe postoperative PVR was 25.8% in eyes managed with cryotreatment versus 2.2% in eyes managed with argon laser photocoagulation (P=0.001). The rate of severe postoperative PVR was not influenced by the other surgical variables. Conclusion: We conclude that cryotherapy may be a risk factor for the development of severe postoperative PVR in retinal detachments associated with grade B PVR.     

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     

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.