Recanalization of venule following experimental retinal branch vein occlusion

Wenderoth, Bray and Johnstone [(1988) Perception, 17, 81-91] measured motion aftereffects induced on stationary vertical sine-wave gratings by horizontally drifting two-dimensional patterns (plaids). The adapting plaid component gratings were simultaneously or alternately presented and were oriented left and right of vertical by 15, 45 or 75 degrees. It was found that aftereffects decreased linearly in the alternating conditions as the plaid component orientations changed but this was not the case in the simultaneous adaptation conditions, a finding taken to be consistent with the hypothesis that one-dimensional aftereffects have a low level site (possibly V1) whereas two-dimensional effects have a higher level site (possibly MT). In three experiments, we have examined in more detail the determinants of aftereffects induced by simultaneous and alternating plaid components. The data suggest that the mechanisms involved are more complex than those put forward by Wenderoth et al. and that plaid perception utilizes both higher and lower level processes which can be referred to, respectively, as an intersection of constraints algorithm and a moving "blob" detector.     

Reversal of blood flow in experimental branch retinal vein occlusion

BACKGROUND: The consequences and management of asymptomatic Actinomyces-like organisms detected on cervical cytologic smears continue to be controversial. CASE: A unilateral tuboovarian actinomycotic abscess was discovered in a woman who had undergone a hysterectomy for uterine leiomyomas. She had had an intrauterine device in place for many years without any symptoms of pelvic inflammatory disease. CONCLUSION: Ascending infection of the upper genital tract by Actinomyces may be clinically inapparent. When Actinomyces-like organisms aer detected on cervical cytologic smears, removal of an intrauterine device should be considered.     

Effect of isovolaemic haemodilution on visual outcome in branch retinal vein occlusion

The relationship between the activation of platelets (PLT) in urine and renal histological findings in children with IgA nephropathy (IgAN), thin basement membrane disease (TBMD), and minimal-change nephrotic syndrome (MCNS) was examined. The ratio of activated PLT to total PLT (activated and nonactivated PLT) was examined by double immunofluorescence using rhodamine-conjugated P selectin antibody (activated PLT) and fluorescein isothiocyanate conjugated PLT membrane glycoprotein antibody (GPIIb/IIIa, total PLT); the effect of urine on activation on PLT was also investigated. The number of activated PLT and the ratio of activated PLT to total PLT in urinary sediments were significantly higher in children with IgAN with diffuse mesangial proliferation than in those with TBMD or MCNS. PLT were activated by addition of urine in 13 out of 27 children with IgAN, and the activity was higher in the urine of those with active glomerular or interstitial lesions, while the urine of children with TBMD or MCNS had no effect. The presence of activated PLT and the effect of urine on PLT activation may be associated with the active glomerular or interstitial lesions in IgAN.     

Natural history of posterior vitreous detachment with early management as the premier line of defense against retinal detachment

PURPOSE: This study was designed to elucidate various aspects of the natural history of posterior vitreous detachment (PVD), in particular the relation between symptomatology and prognosis as it relates to management of patients with the earliest symptoms of PVD. METHODS: A prospective study of 350 consecutive patients with PVD was performed, excluding all patients referred from an ophthalmologist, those with symptoms of more than 3 months in duration, and those with a history of ocular trauma, except for cataract surgery. Aphakia was present in 21 eyes, and 50 patients were bilaterally involved. RESULTS: Of 163 patients who had one to two floaters as their presenting symptom, with or without light flashes, a retinal tear developed in 12 (7.3%). Of 31 phakic eyes with secondary retinal tears on initial examination, 9 (29%) had one to two floaters and light flashes as the only symptoms. Of eight phakic eyes that initially, or eventually, had a retinal detachment, three (37%) had an interval of 2 1/2 to 3 weeks before visual field loss, during which they noticed only one to three visual floaters plus light flashes as their only symptoms. This early stage in which symptoms are detectable is crucial in terms of providing an opportunity for early treatment that might prevent retinal detachments. CONCLUSIONS: The prompt and conscientious vitreoretinal examination of each patient older than 45 years of age who experiences vitreous floaters, even though limited to one or two, should be undertaken without delay. This practice, combined with expeditious treatment of any secondary retinal tears, provides the most effective known means of preventing rhegmatogenous retinal detachment, and currently it appears to be neglected. A national public educational effort should be pursued to publicize the importance of these symptoms.     

Role of electroretinography in the prognosis of central retinal vein occlusion

The aim of the study is to evaluate the role of electroretinography in diagnosis of central retinal vein occlusion CRVO. There are two forms of this entity, each of them having a different prognosis. While haemorrhagic form has a better outcome, with fairly good prognosis for vision, ischaemic form usually develops many complications: macular oedema, neovascularisation of the retina or optic disk, neovascular glaucoma, and possible blindness. Three months after the onset, when oedema and retinal haemorrhages are usually resolved, it is possible to perform fundus fluorescein angiography (FFA) and make differentiation between the two forms of the disease. However, neovascular glaucoma may challenge the vision even before the diagnosis of ischaemic form becomes possible by observing the fundus or by performing FFA. Trying to foresee the course of the disease, and thus to help a patient with panretinal photocoagulation, we performed electroretinography (ERG) in each patient just after the onset of the disease. The prospective study included 40 patients with CROV which lasted less than three months and without any complication. Two parameters were examined: scotopic "b" wave and photopic b/a ration. By ERG action potentials from the retina after its stimulation with light, are recorded. Scotopic "b" wave generates in bipolar layer from Muller's and bipolar cells. Photopic b/a ratio is a ration of two waves, "b" and "a" in photopic conditions and is a good indicator of saturation of the retina with blood and oxygen. Visual acuity, applanation tonometry, examination of the fundus after dilatation of pupils with Sol. Mydriacili were performed in each patient. Each patient was examined by ERG in scotopic and photopic conditions. The results were as follows: Scotopic b wave per se could not indicate potential complications, while b/a ratio was a good predictor of possible complications when its value was less than 1.25. CONCLUSION: Electroretinography, which can be performed at any time after the onset of the disease may be a good indicator of retinal perfusion and oxygen saturation, by giving the ratio of b and a waves under photopic conditions. The status of Muller's cells and bipolar cells is reflected in the scotopic b wave. In a prospective study forty patients with CRVO of less than three months duration and without neovascularisation were studied with the use of ERG, both in scotopic and photopic conditions. Our results suggest that the b/a ratio may be a good predictor of the development of retinal, disk and iris neovascularisation by showing the degree of retinal ischaemia, while the scotopic b wave cannot be used for such evaluation. Predicting the new vessel development by ERG may save the useful vision and prevent a disastrous outcome, blinding and painful neovascular glaucoma by performing panretinal photocoagulation.     

Arteriolar constriction in the treatment of branch retinal vein occlusion. Initial experience

A clinically simple and logical classification of pronation deformity in cerebral palsy into four groups is presented. The appropriate procedure for each group is defined. The validity of this classification is documented with our results in 32 patients.     

The effect of retinal cryoapplication on the vitreous

Long-term clinical trials using bone mineral density (BMD) measurements are now commonplace. It is important to maintain a high standard of quality control. In this study two methods of monitoring quality control measurements of dual-energy X-ray absorptiometry (DXA) equipment have been compared using receiver operating curve (ROC) analysis: Shewhart multi-rule charts and Cusum charts. Computer-generated faults within daily spine phantom measurements were used. The Charts were then applied to 3 years of quality control data from one machine and the results related to hardware faults, random events and changes in the underlying BMD measurement. In the ROC analysis the Shewhart multi-rule chart performed as well or better than the cusum chart, but the stringency of the rules must be tightened to obtain optimal performance.     

Laser-induced chorioretinal venous anastomosis for nonischemic central or branch retinal vein occlusion

Sea urchin embryos have provided excellent material for experimental and molecular analyses of the processes of cell and axis specification during embryogenesis. These studies revealed the tremendous developmental plasticity of cells in early embryos and the roles that cell-cell interactions play in determining cell fates. Details concerning sea urchin development can be found in a number of excellent reviews. This review summarizes experimental and molecular studies relating to axis determination and cell fate specification in echinoid embryos. Correlations are drawn from research carried out on the development of axial systems in other organisms.     

Management of retinal vein occlusion

Retinal vein occlusion is a common cause of visual loss. The clinical features, pathogenesis, aetiology and management of this condition are presented and discussed. It is an advantage to involve both the physician and the ophthalmologist in the management of the condition.     

Acute posterior multifocal placoid pigment epitheliopathy with bilateral central retinal vein occlusion

This study utilised autoradiography to examine [125I]-Bolton Hunter substance P (BHSP) binding in postmortem human visual cortex. In the primary visual area, layers I-III, IVC and VI exhibited low levels of BHSP binding, while high levels were observed in layers IVB and V. Because cells in layers IVB and V are known to be involved in processing direction-specific stimuli, it is possible that SP plays a role in modulating this visual process.     

Fluorescein angiography versus ERG for predicting the prognosis in central retinal vein occlusion

Dr. Roa was the first professor of the Faculty of Medicine of the University of Chile to give an ethics course to medical students, even when the importance of formal teaching of medical ethics was not yet recognized internationally. His efforts contributed to the creation of the Center for Bioethical and Humanistic Studies in 1988 and to the creation of official ethics courses for first and sixth year medical students in 1993. During 20 years, be chaired the Ethics Committee of the Faculty of Medicine of the University of Chile. He also promoted a diffusion program about medical ethics through meetings, conferences and symposia. He was responsible for the Ministry of Health's decision to create ethics committees in public hospitals in 1988 and for the Presidental decision about organ transplantation in 1995. He carried out anthropology courses and gave numerous lectures on humanistic aspects of medicine. His ethical principles are resumed in what he called the "ethics of generosity", in which the dignity of human beings is respected above all, in his opinion, the way civilizations see goodwill has been preponderant in the course of history. The recent proposal to teach humanistic fundamentals to medical students is a tribute to the memory of Professor Roa.     

Decreased nitric oxide production accounts for secondary arteriolar constriction after retinal branch vein occlusion

PURPOSE: After retinal branch vein occlusion (BVO), the arteriole crossing the occluded territories is often constricted. This constriction persists up to several weeks and is correlated with the development of extended territories of nonperfused capillaries. These are results of an investigation supporting the hypothesis that decrease in the production of nitric oxide (NO) accounts for the observed arteriolar constriction. METHODS: Preretinal [NO] was measured using an NO microprobe in the anesthetized miniature pigs, before and during the first 4 hours after experimental branch vein occlusion. Modifications of arteriolar diameter were correlated to preretinal [NO] changes. The retinal arteriolar sensitivity to constitutive NO was checked by applying preretinal puff injections of nitro-L-arginine (L-NA) after both systemic hypoxia and branch vein occlusion. RESULTS: Two hours after branch vein occlusion there was a 73.7 +/- 4% decrease in preretinal [NO] and a simultaneous 25.4 +/- 3.4% decrease in the diameter of the arteriole in the affected territory. Both persisted for at least 4 hours after branch vein occlusion. Applying a puff of L-NA to an arteriole previously dilated by systemic hypoxia induced a vasoconstriction. However, no arteriolar constriction was observed when a puff was applied to an arteriole after branch vein occlusion. CONCLUSIONS: These results show that experimental branch vein occlusion induces in the affected retina an impairment in the release of constitutive NO and an arteriolar constriction, which, in turn, contributes to the development of hypoxia in tissue and neuronal swelling and death in the inner retina.     

Experimental retinal branch vein occlusion. 4. Pathological changes in the middle and late stage

Retinal branch vein occlusion in macaca monkeys (Macaca irus) was produced by dye laser photocoagulation, and observed histopathologically from five days to one year after photocoagulation. Ten days later, retinal edema and hemorrhage observed at an early stage gradually decreased. Two weeks later, capillary bed closure areas were observed in fluorescein angiography. The capillary closure was not reversible when disturbance of the retinal circulation continued for more than three or four days after photocoagulation. Three months later, dry retina was observed in the capillary bed closure areas. One year later, the retina was severely degenerated and thinned. In these retinal areas, capillary lumens observed microscopically were occluded by cellular components. Sheathing of large veins was observed in these retinal areas. The walls of these large veins were thick and fell into hyaline degeneration. Their lumens were narrowed or obstructed. During the period of observation, retinal neovascularization was not observed.     

Precipitation of hard exudate after resorption of intraretinal edema after treatment of retinal branch vein occlusion

BACKGROUND: The use of centrally positioned venous catheters plays an indispensable role in the care of infants and children. METHODS: Since 1992 the authors have seen nine patients who experienced fragmentation and migration of catheter fragments into the central circulation. The patients ranged in age from 6 days to 15 years. RESULTS: Sites of migration included pulmonary artery (five patients), superior vena cava (two patients), hepatic vein and innominate vein (one patient). The elapsed time from recognition of retained catheter fragments until retrieval ranged from a few hours to 6 weeks. CONCLUSION: All retained fragments were successfully removed during cardiac catheterization without complications.     

Outcome after vitrectomy in rhegmatogenous retinal detachment and dense vitreous opacities

To more efficiently reduce the risk of coronary heart disease with lipid lowering therapy, cost effectiveness analysis offers an important tool to best determine how to allocate inherently limited resources to improve the health of both individuals and society. Formal economic analysis of the most recent clinical trials with the 3-hydroxymethylglutaryl coenzyme A reductase inhibitors (statins) suggest that secondary prevention of coronary heart disease is very cost effective compared to existing treatment and prevention strategies. Primary prevention is also cost effective but has a much wider range of cost effectiveness depending on an individual baseline risk. Cost effectiveness can be better maximized in primary prevention by treating patients at the highest absolute risk of coronary heart disease. The debate about lipid lowering therapy will now shift from that of efficacy and safety, to that of cost and cost effectiveness. Defining the optimal treatment thresholds for intervention in primary prevention will become a major focus of investigation.     

A case of retinal detachment in Kniest dysplasia treated with vitreous surgery

We report a case of retinal detachment with Kniest dysplasia for which vitreous surgery was effective. The patient was a 7-year-old female who had the typical ocular and physical findings of this disease. Visual acuity was light perception alone due to a hypermature cataract and bullous retinal detachment. We performed cataract surgery and pars plana vitrectomy, and used silicone oil tamponade. After seven months, the silicone oil was removed, and visual acuity improved to 0.09. We conclude that bullous retinal detachment with Kniest dysplasia can be treated by vitreous surgery in combination with the use of silicone oil tamponade.     

Thrombin-antithrombin III complex in acute retinal vein occlusion

PURPOSE: To determine whether quantitative differences in systemic hypercoagulable state could be identified among patients with retinal vein occlusion at various sites of occlusion. METHODS: The value of thrombin-antithrombin III complex was determined in 57 patients with retinal vein occlusion within 1 month after the subjective onset of retinal vein occlusion and in 15 age-matched normal controls. RESULTS: Levels of log thrombin-antithrombin III complex were significantly higher in the patients with proximal retinal vein occlusion in which the occlusion site is at the optic disc (mean +/- SD, 0.493 +/- 0.389) than in those with distal retinal vein occlusion in which the occlusion site is away from the optic disc (0.312 +/- 0.150, P = .025) and in the normal controls (0.294 +/- 0.151, P = .020). There was no significant difference between the distal retinal vein occlusion and the normal controls (P = .720). More patients with proximal retinal vein occlusion showed elevated thrombin-antithrombin III complex values more than 3.9 ng/ml than those with distal retinal vein occlusion (8/29 vs 1/28, P = .025). Of nine patients showing an initial value of thrombin-antithrombin III complex of more than 3.9 ng/ml, repeated measurements were obtained in eight patients, who showed reduced value of thrombin-antithrombin III complex in the normal range in several months. CONCLUSIONS: A systemic hypercoagulable state, which could be demonstrated with the elevation of thrombin-antithrombin III complex value, may contribute more to the development of retinal vein occlusion with thrombus at or near the trunk of the central retinal vein than those with thrombus at branch veins away from the optic disc in the retina.