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At least 127 records · Page 7Linked to original sources
PubMed1996

Modulation of retinal endothelial barrier in an in vitro model of the retinal microvasculature.

The prediabetic/diabetic condition functionally alters the microvascular bed of the eye and the breakdown in the transvascular barrier may be produced by changes in the retinal endothelial barrier. To better understand how retinal microvessel barrier is maintained and is altered in vivo this study applies and extends our previously described in vitro permeability technique to study retinal endothelial monolayers. The model of the retinal microvasculature consists of retinal capillary endothelial cells cultured on porous microcarrier beads and perfused in chromatographic 'cell-columns'. This model design relies on indicator-dilution techniques to measure the permeability of the retinal endothelial monolayer and detects small changes in retinal endothelial permeability produced by treatments. Bovine retinal capillary endothelial cells (RCE) were obtained using an endothelial selective media. RCE were seeded at 3 x 10(4) cells cm-2 of fibronectin-coated gelatin microcarriers. After 7 days of microcarrier culture, microcarriers were poured to form columns 0.66 cm in diameter and 1.6 cm in length. The cell-column elution patterns of coinjected optically absorbing tracers (blue dextran 2 x 10(6) Da; cyanocobalamin 1355 Da; sodium fluorescein 376 Da) were analysed to estimate the permeability of the RCE monolayers covering the microcarriers. Scanning electron microscopic examination showed complete monolayer formation on the surface of the microcarriers. We found that baseline monolayer permeability averaged 7.57 +/- 0.57 x 10(-5) cm sec-1 for cyanocobalamin and 9.29 +/- 0.78 x 10(-5) cm sec-1 for sodium fluorescein (mean +/- S.E.M., n = 39). Permeability did not increase over 2 hr of cell-column perfusion. Permeability was decreased by 1 micron isoproterenol (n = 3) and increased by 1 microgram ml-1 cytochalasin D (n = 5). This is one of the first reports of in vitro permeability values for the transport barrier formed by retinal microvascular endothelial cells. Furthermore, the endothelial component of the retinal barrier is dynamic, and is enhanced by isoproterenol and diminished by cytochalasin D.

Animals↗
PubMed1997

[Acute retinal necrosis. Silicon oil tamponade in retinal detachment].

BACKGROUND: Because retinal necrosis syndrome seldom occurs, we present our results of silicone oil tamponade for associated retinal detachment. PATIENTS AND METHODS: Thirteen eyes from 13 patients undergoing retinal reattachment surgery for retinal detachment associated with acute retinal necrosis in a consecutive series between January 1988 and June 1995 were followed up. Patients were 25 to 56 years of age. Four patients had acquired immune deficiency syndrome (AIDS). Five eyes that were operated on with cryopexy and scleral buckling received vitrectomy, membrane peeling, silicone oil tamponade and endolaser treatment in a second operation. Eight eyes were primarily operated on with cryopexy, encircling buckle, vitrectomy with membrane peeling, silicone oil tamponade and endolaser treatment. All patients were treated with acyclovir. RESULTS: Postoperative complete reattachment was observed in 12 eyes and persistence of a peripheral detachment in one eye. Vision improved in eight eyes, but only five eyes achieved 20/200 or better vision. Limited functional results in our series were caused by retinal ischemia, optic atrophy and macula scars. After a median of 9.3 months silicone oil was removed in nine eyes. No retinal redetachment or recurrent retinitis was observed during a follow-up time of at least 6 months. CONCLUSIONS: Vitrectomy and silicone oil tamponade allowed all cases of retinal detachment associated with acute retinal necrosis to be successfully repaired. Further studies must be conducted to find out how we can improve the visual outcome-perhaps by earlier therapy with acyclovir or earlier vitrectomy.

Acquired Immunodeficiency Syndrome↗
PubMed2004

Retinal vein cannulation with prolonged infusion of tissue plasminogen activator (t-PA) for the treatment of experimental retinal vein occlusion in dogs.

PURPOSE: To evaluate the feasibility, safety, and efficacy of local thrombolytic agents directly injected into occluded retinal veins in an experimental animal model. DESIGN: Experimental animal study. METHODS: This experimental study was performed in two phases. In phase 1, 15 enucleated porcine eyes and 8 in vivo canine eyes were used for the development of the instrumentation and surgical technique required for retinal vein cannulation with prolonged intravascular infusion. In phase 2 of this study, experimental branch retinal vein occlusion was photo-chemically created using an intravenous injection of rose bengal followed by diode laser photocoagulation in eight eyes of eight dogs. Four eyes were treated by retinal vein cannulation and an injection of tissue plasminogen activator (t-PA) using a specifically designed microcatheter, while the remaining four eyes were untreated (control group). The total amount of t-PA injected intravenously ranged from 400 to 1000 mug, infused over a period ranging from 25 to 45 minutes with a mean pressure of 40 psi, resulting in a mean injection flow rate of 0.05 ml/min. The dogs underwent clinical examination, fluorescein angiography, and histologic examination. Main outcome measures were: Achievement of prolonged intravascular infusion of t-PA, changes in fundus appearance, fluorescein angiography, and histology. RESULTS: A microcatheter instrument and a surgical technique for retinal vein cannulation with prolonged intravascular infusion were developed. Cannulation and t-PA infusion for a period of at least 30 minutes was achieved in all four treated eyes with experimental branch retinal vein occlusion. No complications were recorded in all treated eyes. One week and 1 month postoperatively, treated eyes exhibited marked decreases in retinal hemorrhages, retinal vein dilation, and tortuosity, whereas nontreated eyes exhibited persistence of these findings. Fluorescein angiography demonstrated improved circulatory flow in treated relative to nontreated eyes. Histologic analysis confirmed the presence of thrombi in nontreated eyes only. CONCLUSIONS: Retinal vein cannulation with prolonged intravascular injection of t-PA is feasible and safe, and this may offer a new treatment option for retinal vein occlusion.

Animals↗
PubMed2005

Results of silicone oil removal in patients with cytomegalovirus retinitis related retinal detachments.

PURPOSE: To evaluate the percentage and risk indicators leading to retinal redetachment in HIV (human immunodeficiency virus) patients with CMV (cytomegalovirus) retinitis related retinal detachments that were repaired with silicone oil, and then subsequently underwent oil removal. DESIGN: Retrospective, noncomparative interventional case series. METHODS: The study cohort consisted of a series of 15 eyes in 14 patients with HIV and CMV retinitis with a retinal detachment (RD) repaired with silicone oil at a single center and followed from the time of the CMV retinitis diagnosis through the time of silicone oil removal. Patient- and eye-specific data regarding demographic and clinical characteristics were collected retrospectively and statistical analyses were performed to compare differences between the eyes that had retinal detachments versus the eyes that remained attached following removal of silicone oil. RESULTS: Eight eyes (53%) redetached after a median of 4.0 months following oil removal. Cataract surgery performed at the time of oil removal was a statistically significant risk factor for redetachment (P = .01). There was a trend for lower CD4 levels to be associated with a higher risk of retinal redetachment. The use of a scleral buckle at the time of surgery (initial RD repair or at the time of oil removal) did not reduce the risk of redetachment. CONCLUSIONS: Approximately half of the eyes with CMV related retinal detachment may safely undergo oil removal. The risk factor for redetachment was simultaneous cataract extraction at the time of silicone oil removal. There was also a trend for lower CD4 levels to be associated with a higher risk of retinal redetachment.

AIDS-Related Opportunistic Infections↗
PubMed2006

Retinal endovascular lysis in ischemic central retinal vein occlusion: one-year results of a pilot study.

PURPOSE: Retinal endovascular lysis is a new therapeutic option for patients with central retinal vein occlusion (CRVO). In this procedure, a fibrinolytic agent is injected directly into a cannulated retinal vein after pars plana vitrectomy. DESIGN: Prospective interventional case series. PARTICIPANTS: Thirteen strictly defined patients with ischemic CRVO. METHODS: Patients with a decimal visual acuity (VA) of 0.2 or worse were scheduled for surgery within the first 5 months after onset of CRVO. A full ocular examination, determination of VA (Early Treatment Diabetic Retinopathy Study charts), and fluorescein angiography were done preoperatively and 6, 12, 26, and 52 weeks postoperatively. MAIN OUTCOME MEASURE: Visual acuity 1 year after retinal endovascular lysis. Secondary study end points were (1) correlation of VA and successful recombinant tissue plasminogen activator injection into a retinal vein, (2) complication rate, and (3) number of additional surgical procedures within the first year after retinal endovascular lysis. RESULTS: All patients had an ischemic CRVO and completed the 1-year follow-up visit. Preoperative decimal VA was 0.063 +0.025/-0.018 (VA range, light perception [LP]-0.2); 6-week postoperative VA, 0.049 +0.024/-0.016 (LP-0.4); 3-month postoperative VA, 0.043 +0.019/-0.014 (LP-0.3); 6-month postoperative VA, 0.035 +0.022/-0.013 (blindness-0.4); and 12-month postoperative VA, 0.04 +0.026/-0.016 (blindness-0.4). Visual acuity changed 1 year after retinal endovascular lysis by -1.923+/-1.619 lines (+6 to -16 lines; P = 0.258). We considered the retinal endovascular lysis procedure to have been technically successful in 10 eyes. Visual changes did not depend on successful lysis. Six eyes developed neovascular glaucoma, of which 2 globes ended up with painful phthisis and had to be removed. Retinal detachment was found in 3 eyes and cataract in 4. Together, the 13 eyes needed 22 additional surgical procedures. Preoperative and postoperative angiographic examinations showed no significant changes. CONCLUSION: Ischemic CRVO patients did not profit from retinal endovascular lysis in this pilot study. Visual results and the risk of developing iris neovascularization and neovascular glaucoma took the natural course. Although these results may be due to the overall bad prognosis of these particular ischemic eyes, the number of postoperative complications is unacceptably high.

Aged↗
PubMed1993

Risk factors for development of rhegmatogenous retinal detachment in patients with cytomegalovirus retinitis.

We studied 259 patients to determine the time-dependent risk and risk factors for the development of retinal detachment in patients with cytomegalovirus retinitis. The six-month and one-year retinal detachment rates (by eye) were 11% and 24%, respectively. Increasing retinal surface involvement outside of the posterior pole and the presence of retinitis activity were found to be the two covariates that best predicted retinal detachment. Eyes with peripheral involvement greater than 25% had a fivefold risk for detachment, compared to eyes with 10% involvement. If there was retinitis activity and more than 25% peripheral (external to major vascular arcades) involvement, the risk increased to 24-fold. The presence of a fellow eye with retinal detachment was not an independent risk factor. These observations should help in the design of a prophylactic trial intended to prevent retinal detachment and should also help ophthalmologists counsel patients with cytomegalovirus retinitis.

AIDS-Related Opportunistic Infections↗
PubMed1991

Antibody indications of secondary and superimposed retinal hypersensitivity in retinitis pigmentosa.

Antibody reactions with recognized retinopathy-inducing retinal antigens may be interpreted to reflect ongoing autoimmune events responsible for some forms of vision loss. We sought evidence of secondary and superimposed retinal hypersensitivity indicated by such antibody reactivity in a random group of patients with retinitis pigmentosa. We identified patterns of immunologic reactivity within members of a group of 52 patients with retinitis pigmentosa, which suggests some patients with retinitis pigmentosa may experience consequential superimposed retinal hypersensitivity. Identifying subgroups of patients with retinitis pigmentosa who exhibit indications of retinal hypersensitivity to known uveitopathogenic retinal proteins may permit the reduction of their rate of retinal degradation by immunomodulation.

Adult↗
PubMed1997

Repair of retinal detachments due to herpes varicella-zoster virus retinitis in patients with acquired immune deficiency syndrome.

PURPOSE: The authors characterize surgical techniques and report results for repair of retinal detachments due to varicella-zoster retinitis in patients with acquired immune deficiency syndrome (AIDS). BACKGROUND: Varicella-zoster virus (VZV) retinitis is a distinctly aggressive infection in patients with AIDS. Retinal detachments occur in the majority of such patients, and contribute to their poor visual prognosis. METHODS: A case series of five eyes in four patients with AIDS and retinal detachments due to VZV retinitis is presented, highlighting surgical technique and results. Pars plana vitrectomy, silicone oil tamponade, and endolaser photocoagulation were used in all cases. RESULTS: Apparent contraction of the necrotic retina was observed, requiring large relaxing retinectomies to achieve retinal attachment in three of the five eyes. Follow up after surgery was 4, 6, 15, 29, and 30 months. Four eyes maintained ambulatory vision and the retinas remained attached. CONCLUSION: Vitrectomy with silicone oil tamponade may be used to preserve ambulatory vision in carefully selected patients with AIDS and retinal detachments due to VZV retinitis. Relaxing retinectomy is a useful technique to achieve and maintain retinal attachment.

AIDS-Related Opportunistic Infections↗
PubMed2006

[Treatment of retinal detachments with giant retinal tear. Retrospective study of 23 cases].

PURPOSE: Report of anatomic and functional results of retinal detachment with giant retinal tear. PATIENTS AND METHODS: Retrospective study of 23 cases of retinal detachment resulting from retinal tear of 90 degrees or more: five had a history of ocular trauma, 14 had myopia, and six had no risk for giant retinal tear. Episcleral surgery was performed on cases of giant retinal tear less than 180 degrees , with no advanced proliferative vitreoretinopathy and no inversion of the retinal flap. A vitrectomy was performed on other cases. Scleral buckle was associated with vitrectomy in cases of advanced vitreoretinopathy. RESULTS: The degree of success in the primary surgery was 50% in vitreoretinal surgery, 75% in vitreoretinal surgery with an encircling scleral buckle, and 86.4% in episcleral surgery. Of the seven failed cases, six patients underwent second-intention surgery: vitrectomy in four cases (primary surgery: the first case, episcleral surgery; the next two cases, vitrectomy; and in the fourth, vitrectomy with an encircling scleral buckle). In the last two cases, vitrectomy with scleral buckle was used (the primary surgery in both cases was vitreoretinal surgery). The final success rate was 78.2%, and the average follow-up was 32 months. Through the last test, postsurgery acute vision improved in 16 cases. CONCLUSION: Vitrectomy is often recommended to repair retinal detachment with giant retinal tear. However, episcleral surgery can be used if the giant tear is less than 180 degrees , the proliferative vitreoretinopathy is not advanced, and the retina flap is not inverted. The scleral buckle must be associated with the vitrectomy in cases of inferior giant retinal tear even if the proliferative vitreoretinopathy is not advanced.

Adolescent↗
PubMed2001

Retinal vascular architecture is maintained in retinal degeneration: corrosion cast and electron microscope study.

PURPOSE: To demonstrate the changes of the retinal vascular architecture in the diffusely degenerated thin retina. METHODS: Three-week-old weanling Wistar Kyoto rats were divided randomly into two groups. One group (n = 20) was fed a vitamin E-deficient solid diet and the other group (n = 20) was fed a solid rat chow diet. Rats were maintained on their respective diets for 14 months and then killed for scanning electron microscopy of vascular corrosion casts, light and electron microscopy and biochemical determinations. RESULTS: The serum level of vitamin E in the E-deficient rats was 1.0 +/- 0.49 microg/ml, while that in the rats fed a normal diet was 13.7 +/- 1.0 microg/ml (Student's t-test, p = 0.0001). In vitamin E-deficient rats, light microscopy showed degenerated retinas only half as thick as normal. Corrosion casts and scanning electron microscopy revealed that the retinal capillaries of the entire retina were decreased in number and scattered with localised narrowing, calibre irregularity and frequent loop formation. In the posterior pole of the retina, some capillaries clustered into small tortuous knots. However, the two-layered architecture of the capillary network in the retina was maintained. The differences in calibre of retinal capillaries between the vitamin E-deficient and normal rats were statistically significant (p < 0.0001). No remarkable abnormal changes were observed in the large retinal vessels other than arterial calibre differences (p < 0.022). No arteriovenous shunts, crossing defects or microaneurysms were seen. Transmission electron microscopy revealed complete disappearance of the photoreceptor outer and inner segments and nuclei. The retinal pigment epithelium contained lipofuscin granules and retinal capillaries with narrow lumens. The capillary endothelial cells were thickened and had scarce cytoplasmic components with vacuoles and irregularly thickened basement membranes. The capillary pericytes had vacuoles. No abnormalities were seen in the control normal rats. CONCLUSION: These findings indicate that the decrease in retinal capillaries in vitamin E-deficient rats is secondary to retinal degeneration. It was assumed that the morphological changes in the capillary network reflected structural damage to the retinal vascular cells caused by free radicals and lipid peroxides generated by oxidation. However, even in such severe degeneration the retinal vascular architecture, including the main artery and vein and two-layer capillary networks, was maintained. This is may be because of the basic anatomical arrangement of the blood vessels.

Animals↗
PubMed2005

Retinal vascular development and pathologic retinal angiogenesis are not impaired in matrix metalloproteinase-2 deficient mice.

PURPOSE: Earlier studies have suggested a role for metalloproteinase-2 (MMP-2) in retinal angiogenesis. To investigate this further, we have studied retinal vascular development and pathologic ischemia-induced retinal angiogenesis in MMP-2-deficient and wild-type mice. METHODS: Vascular development of the retina was studied in retinal flatmounts, whereas pathologic retinal angiogenesis was analyzed in retinal flatmounts and on histologic sections using a model of ischemia-induced retinopathy. The time course of MMP-2 mRNA expression was determined by in situ hybridization and real-time polymerase chain reaction (PCR). RESULTS: Formation of the retinal vascular plexus was not significantly different in MMP-2-deficient mice as compared to wild-type mice. In ischemia-induced retinopathy, there was an increased formation of extraretinal neovascular tufts in the MMP-2-deficient mice (p < 0.05). MMP-2 mRNA expression did not correlate to either retinal vascular development or to ischemia-induced formation of extraretinal vascular tufts. CONCLUSIONS: The current data suggest that MMP-2 is not essential for either retinal vascular development or pathologic retinal neovascularization in the mouse.

Animals↗
PubMed1996

Retinal detachments with crescent-shaped retinal breaks in patients with atopic dermatitis.

BACKGROUND: There has been increasing number of reports of retinal detachments associated with atopic dermatitis. However, little is known about the etiology of these rhegmatogenous detachments. The authors encountered two patients with retinal detachments associated with a crescent-shaped retinal break combined with another break located at or anterior to the ora. METHODS: Preoperative and intraoperative findings in these cases were evaluated. RESULTS: In both cases, vitreoretinal adhesions were observed on the anterior and posterior edges of a crescent-shaped retinal break. Vitreous traction between the crescent-shaped retinal break and the break located at or anterior to the ora was also observed. No abnormalities were detected in the choroid in either case. A possible causative factor for the retinal detachments in these patients was the habit of rubbing and slapping their faces, apparently to alleviate extreme itching. CONCLUSION: Crescent-shaped retinal breaks, which were different from conventional horseshoe tears or atrophic retinal holes, were an interesting and unusual feature of two patients with atopic dermatitis and rhegmatogenous retinal detachments. These crescent-shaped retinal breaks may have been caused by ocular contusion.

Adolescent↗
PubMed1998

Cyanoacrylate glue in the repair of retinal detachment associated with posterior retinal breaks in infants and children.

PURPOSE: To share the authors' experience with cyanoacrylate glue in posterior retinal breaks associated with retinal detachments in infants and children. METHODS: A retrospective study was performed of four consecutive pediatric patients who underwent vitreoretinal surgery for retinal detachment associated with posterior retinal breaks, for which cyanoacrylate glue was used. RESULTS: In three of the four patients, successful retinal reattachment with visual function was achieved by vitreoretinal surgery and cyanoacrylate placed on the apposed edges of posterior retinal breaks or used to plug a break (postoperative follow-up was 1.5-2 years). In two successful cases, the glue was applied onto the break while the retina was detached, which resulted in closure of the retinal breaks and reattachment of the retina in both cases. CONCLUSIONS: Cyanoacrylate creates a permanent closure of retinal breaks and may be useful in select cases of infant retinal detachment with posterior retinal breaks in which current available treatment failed or would fail.

Administration, Topical↗
PubMed1997

Retinal detachment caused by retinal dialysis.

PURPOSE: To determine the characteristics of patients developing retinal detachment secondary to retinal dialysis in Western Australia and to confirm the clinical impression that these patients had a low rate of proliferative vitreoretinopathy (PVR). METHODS: A retrospective analysis of the records of 1601 consecutive patients with rhegmatogenous retinal detachment identified 71 patients in whom the retinal detachment was caused by a retinal dialysis. RESULTS: The majority of these patients were young adults (mean age of 30 years) and the male to female ratio was 1.3:1. Seventy per cent of patients provided a history of significant trauma to the affected eye. Sporting injuries, assault, and motor vehicle injuries together accounted for 72% of identifiable trauma. Examination revealed a dialysis of the inferotemporal quadrant in 75% of cases and despite obvious signs of chronicity of the associated retinal detachment (such as intraretinal macrocysts and demarcation lines) in approximately one-third of the eyes, only 5.6% developed grade CI PVR either pre- or postoperatively. CONCLUSION: The present study supports the view that it is the low rate of PVR that explains the good prognosis and high surgical success rate for retinal detachments caused by retinal dialysis. It is postulated that a major reason for the low rate of PVR is that the vitreous base attachment to the posterior margin of a retinal dialysis acts as a significant barrier to the migration of potentially proliferative retinal pigment epithelial cells. This may lead to containment of the responsible proliferative cells within the loculated subretinal space.

Adolescent↗
PubMed2005

[The characteristics of retinitis pigmentosa with retinal vascular occlusion].

OBJECTIVE: To observe clinical features of Retinitis pigmentosa with retinal vascular occlusion and its prognosis. METHODS: To analyze the clinical Data in 18 cases retrospectively using fundus examination, fundus fluorescein angiography, indocyanine green angiography, electroretinogram, visually evoked potential etc. Gene screening was performed in 3 cases. RESULTS: the major clinical manifestations of the disease were optic atrophy, vascular attenuation to obliteration, widespread retinal pigment epithelium atrophy with depigmentation and/or fine pigment spots, total or nearly total a and b wave were extinct in the examination of electroretinogram. All this manifestations were compatible with that of typical Retinitis Pigmentosa (tapeto-retinal dystrophy). It also had its unique features, such as total or nearly total vascular obliteration, marked optic atrophy in later stage, and choroidal vessels abnormal. Gene mutation was not found in gene encoding area of RHO gene of No: 3 chromosome and of RLBPI gene of No: 15 chromosome. vision loss in this kind retinitis pigmentosa is much faster than that of typical retinitis pigmentosa. CONCLUSION: Retinitis pigmentosa with retinal vascular occlusion may belonged to a kind of tapeto-retinal dystrophy, vascular progressive obliteration was probably its associated disease.

Adolescent↗
PubMed1991

[Retinal nerve fiber layer photography in retinal vein occlusion].

In six eyes we found typical signs that could serve as criteria for the differentiation of ischemic from non-ischemic retinal branch vein occlusion. Perimetry showed a mean defect (in the affected area) of more than 10 dB in eyes with defects in the retinal nerve fiber layer in contrast with 5 dB on one eye without nerve fiber defects. Secondly, fluorescein angiography showed ischemic areas in all eyes examined with localized defects in the photographs of the retinal nerve fiber layer. Damage of the retinal nerve fiber layer was observed before capillary obliteration could be detected by fluorescein angiography. Thirdly, semiquantitative optic disc morphometry demonstrated that using the difference between pallor and excavation as the only sign in ascending optic atrophy is not always useful. Fourthly, photography of the retinal nerve fiber layer showed that there is no correlation between the extension of the ischemic area and the sector angle of the defect of the retinal nerve fiber layer. Photography of the retinal nerve fiber layer can differentiative ischemic from non-ischemic retinal branch vein occlusion because of the qualitative detection of localized retinal nerve fiber layer defects. Consequently, this method is not only of great clinical importance for the diagnosis of different optic lesions, but is also useful for the prognosis and management of occlusion of the retinal branch vein.

Female↗
PubMed1997

The effect of acute experimental retinal vein occlusion on cat retinal vein pressures.

PURPOSE: Retinal ischemic damage associated with retinal vein occlusion is exacerbated by fluid extravasation and hemorrhage, which may be caused by increased permeability, elevated intravascular pressure, or both. Direct measurement of the retinal vein pressure in the cat after acute experimental retinal vein occlusion may define the role of intravascular pressures in fluid extravasation associated with this condition. METHODS: Intravenous retinal pressure measurements were obtained using a micropipette connected to a servonull device and positioned by a robot micromanipulator, while a major retinal vein near the optic disc was occluded by argon laser radiation delivered through an optical fiber positioned by a manual micromanipulator. After occlusion, retinal vein pressures were measured on both sides of the occlusion site at a controlled intraocular pressure of 20 mm Hg. RESULTS: Upstream of the occlusion site, the retinal vein pressures were not greatly elevated, although they were significantly different from controls. Downstream vein pressures were significantly lower than controls, but vascular collapse near the optic nerve was not observed. CONCLUSIONS: In retinal vein occlusion, venous pressures in a segmental retinal circulatory bed are not substantially elevated, thus implying the presence of a pressure-release mechanism and implicating vascular damage for the increased transvascular fluid flux. The lack of vascular collapse downstream of the occlusion site suggests collateral communication before a large intraocular pressure-dependent resistance segment that lies between the intraocular and extraocular vessels.

Acute Disease↗
PubMed1998

[Measurement of retinal blood flow velocity by scanning laser ophthalmoscopic fluorescein fundus angiography in experimental retinal vein obstruction].

To study the role of arterial blood dynamics in the thrombogenesis of thrombin-induced experimental retinal vein obstruction, the retinal blood flow velocity was evaluated using scanning laser ophthalmoscopic fluorescein videoangiography in an experimental rabbit retinal vein obstruction model. Retinal vein obstruction was made by transadventitial direct instillation of thrombin to the retinal vessels from the vitreous side. The blood flow velocity in the retinal artery and vein was estimated by measuring the passing velocity of the flow head of the dye bolus and venous filling time, respectively. 23 animals were treated with thrombin and compared with 18 controls not treated. In the control group retinal artery blood flow velocity and retinal venous fluorescein filling time was 5.3 +/- 1.1 mm/sec (mean +/- standard deviation) and 6.2 +/- 1.2 sec, respectively. In the treated group the values were 5.7 +/- 1.3 mm/sec and 5.8 +/- 1.0 sec before the thrombin administration, and 3.0 +/- 0.9 mm/sec at 24 hours after its administration, and 5.7 +/- 2.0 sec and 4.0 +/- 1.5 mm/sec and 4.5 +/- 1.4 sec at 48 hours after the administration. These results indicate that a decrease in retinal artery blood flow velocity is strongly involved in the thrombogenesis in thrombin-induced experimental retinal vein obstruction.

Animals↗