NO donors and experimental retinal vein occlusion]

PURPOSE: The development of extended territories of nonperfused capillaries after branch vein occlusion (b.v.o.) is correlated to the secondary constriction of the arteriole crossing the occluded territory. Local NO release is impaired soon after b.v.o. and accounts for the secondary arteriolar constriction. In this report we present evidences showing that administration of an NO donor can reverse the secondary arteriolar vasoconstriction observed after b.v.o. MATERIAL AND METHODS: Simultaneous preretinal NO profiles and arteriolar diameter measurements were performed in miniature pigs after experimental b.v.o. The effect of preretinal microinjections of the NO-donor Sodium Nitroprusside on the arteriolar diameter was studied. RESULTS: A significant arteriolar vasoconstriction occurring in parallel with a pre-retinal [NO] decrease was observed 4 hours after b.v.o. Microinjection of the NO-donor SNP caused a segmental, reversible arteriolar dilatation. CONCLUSION: The present results, suggest that local NO supply in the first hours following b.v.o. may contribute to protect the retina against ischemic injury.     

Capillary blood flow in acute branch retinal vein occlusion

PURPOSE: To study retinal capillary blood flow during the acute stage of induced branch retinal vein occlusion (BRVO) in the feline retina and the effect of systemic blood pressure during this event. METHODS: Known fractions of the animal blood cells were labeled by a fluorescent marker and tracked by an electro-optical device as they flowed within the retinal microcirculation. Branch retinal vein occlusion was induced by photocoagulation of a large vein at the optic disk rim. The findings were video recorded and analyzed by computerized image processing. RESULTS: Reversed capillary blood cell flow from the blocked vein was noted immediately following occlusion of the vein. Two patterns of reversed capillary flow were identified: one from the blocked vein to a terminal arteriole and the other from a blocked vein to another vein via a junction with a terminal arteriole. Increased systemic blood pressure decreased the reversed flow in both flow patterns. CONCLUSIONS: 1) Flow deviation to nearby retinal arterioles or veins (shunting) through the normal capillary system is an immediate hemodynamic event following acute BRVO. 2) The reversed capillary flow is affected by the systemic blood pressure.     

Changes of retinal capillary blood flow in age-related maculopathy

Background: To investigate retinal capillary blood flow characteristics in patients with age-related maculopathy (ARM). Methods: Retinal capillary blood volume (VOL), blood flow (FLOW), and velocity (VEL) were measured in four macular sectors (I, II, III, IV) and in two areas beyond the temporal superior and inferior major vessel arcades (V and VI) in: 10 eyes with early ARM (drusen ≥63 μm and/or atrophy of the retinal pigment epithelium, RPE, <175 μm and/or proliferation of RPE), 13 with late ARM (exudative), 10 with late ARM (fibrotic), 14 normal eyes of 14 children of patients with ARM, and in 4 age- and sex-matched control groups using the Heidelberg retinal flowmeter (HRF). Statistical analysis was performed with the exact Wilcoxon test using an additional adjustment procedure by Bonferroni-Holm. Results: As compared to the control group, there was no significant change of VOL, FLOW, and VEL in patients with early ARM. In patients with late ARM (exudative), there was a significant higher FLOW in sectors I, II, and IV and a higher VOL and VEL in sectors III and IV. The group with late ARM (fibrotic) showed a reduction of VOL and FLOW in sectors I–IV and of VEL in sectors II and IV. In children of ARM patients, VOL, FLOW, and VEL of sectors I–VI did not differ from the control group. Conclusion: HRF measurements in patients with ARM indicate an increased macular retinal capillary blood flow in patients with the exudative form of late ARM and a decreased macular perfusion in those with the fibrotic form. Received: 7 February 2000 Revised: 30 June 2000 Accepted: 3 July 2000     

Evaluation of pulsatile choroidal blood flow in branch retinal vein occlusion

BACKGROUND: The present study was undertaken to compare pulsatile choroidal blood flow in patients with branch retinal vein occlusion (BRVO) with the values in normal controls. METHODS: The study included male and female patients with manifest BRVO (n=16) and a healthy sex- and age-matched control group (n=36). Fundus pulsation amplitude (FPA) was measured in the fovea by laser interferometry to assess pulsatile choroidal blood flow. RESULTS: The FPA in eyes with BRVO (4.4 microm) was significantly higher than in the fellow eye (3.8 microm; P<0.0005). There was also a significant difference between the affected eye of the patients and the healthy control group (3.3 microm; P<0.0009). CONCLUSION: The increase in FPA indicates increased choroidal blood flow resulting from some local mechanisms compensating for the decrease in retinal blood flow.     

Changes in the ocular and orbital blood flow in patients with retinal detachment treated surgically]

Sixty-eight patients with dystrophic regmatogenic detachment of the retina and 78 controls with different clinical refraction were examined by triplex scanning of the eyeball. Bloodflow parameters in the orbital artery, central retinal artery, posterior short ciliary arteries were evaluated before and in various periods after the operation. Characteristics of the bloodflow in the ocular and orbital arteries in myopia, detachment of the retina in the presence of myopic and emmetropic refraction, proliferative vitreoretinopathy of various degrees and patterns of its progress during the postoperative period were determined and time course of bloodflow parameters evaluated in some types of interventions. Hemodynamic parameters of the orbital artery and posterior short ciliary arteries were significantly related to the degree of proliferative vitreoretinopathy and its postoperative progress.     

Changes in retinal electrical response due to different size of experimental retinal detachment]

To investigate the influence of the size of detachment to function of the detached retina, transretinal ERG (TR-ERG) was recorded from experimentally detached retina. Retinal detachment 4 or 8 mm in diameter was made by injecting sodium hyaluronate in the subretinal space. The TR-ERG was recorded for two hours from the detached retina by a double barreled microelectrode of which a longer tip entered into the subretinal space of the detached retina while a shorter one remained in the vitreous. Vitreal ERG (VERG) was simultaneously recorded between the shorter electrode and a scleral electrode. The b-wave amplitude of the TR-ERG recorded from the retina with 4 mm detachment decreased two hours after detachment, whereas the b-wave recorded from the retina with 8 mm detachment remarkably decreased 30 min after detachment and was stable up to two hours. There were no significant differences in amplitudes of VERG b-waves between 4 and 8 mm detachments during the experimental course. Less extensively detached retina maintained its function to a greater degree than the largely detached retina. The volume of the subretinal space may influence the viability of the detached retina by changing the concentration of nutrients.     

Colour Doppler assessment of blood flow in eyes with central retinal vein occlusion

PURPOSE: To assess the blood flow changes in eyes with central retinal vein occlusion (CRVO) and compare these values with values of fellow eyes and eyes of normal subjects. METHODS: 25 eyes of 25 consecutive newly diagnosed patients with CRVO comprised the study group. Their fellow eyes and those of 25 healthy subjects were the control group. All patients underwent a complete ophthalmological examination. Eyes with CRVO were classified into two groups as non-ischaemic and ischaemic by fundus fluorescein angiography. Colour Doppler imaging was performed with a Toshiba Sonolayer SSH-140A and 7.5-MHz linear array probe. Maximum systolic velocity (V(max)), end-diastolic velocity (V(min)) and resistive index (R(i)) values were noted for each of the central retinal artery (CRA), central retinal vein (CRV) and ophthalmic artery (OA). These parameters were compared with those of the fellow eyes and both eyes of the control group. RESULTS: Mean ages were 63.55 and 61.45 years in the CRVO and control groups, respectively. Age and sex distributions were statistically identical in both groups. When we compared the eyes with CRVO to the control group, no statistically significant difference existed between the two groups with regard to the V(min) and R(i )values of the CRA and CRV. However, V(max ) values of the CRA and CRV were significantly lower in CRVO eyes when compared to the control group. The CRVO group and control group had similar V(max), V(min ) and R(i) values for the OA. Only the V(max) was significantly lower in the CRV in eyes with CRVO when compared to the unaffected fellow eyes. No statistically significant difference could be detected between any of the parameters of CRA, CRV and OA of the ischaemic and non-ischaemic CRVO groups. CONCLUSIONS: More data on broader series need to be obtained in order to decide on the practical use of colour Doppler imaging in the differentiation of ischaemic eyes from non-ischaemic eyes in CRVO.     

Change in retinal arterial blood flow in the contralateral eye of retinal vein occlusion during glucose tolerance test

PURPOSE: To investigate the changes in retinal blood flow (RBF) during a 75-g oral glucose tolerance test in the contralateral eye of patients with retinal branch vein occlusion (BRVO).METHODS: Seventeen patients with BRVO were included. None had a known history of diabetes mellitus. The blood velocity and vessel diameter of the upper temporal retinal artery in the contralateral eye were measured using laser Doppler velocimetry with an eye-tracking system before and 1, 2, and 3 h after oral intake of 75 g glucose. Blood sugar, systemic blood pressure, and intraocular pressure were monitored. Eleven healthy volunteers were examined similarly as control.RESULTS: Nine patients (53%) with BRVO had an abnormal pattern on the glucose tolerance test. RBF significantly increased at 1, 2, and 3 h in eight patients with normal glucose tolerance. The changes in RBF primarily resulted from changes in vessel diameter; the blood velocity did not change significantly. The nine patients with impaired glucose tolerance or diabetes mellitus had a RBF pattern that was significantly lower at 2 and 3 h than those with normal oral glucose tolerance. In the control group, all 11 volunteers showed the same increases in RBF at 2 and 3 h as the BRVO patients with a normal glucose pattern.CONCLUSION:A relatively high number of patients with BRVO had an abnormal pattern on glucose tolerance testing. Glucose intake increased RBF in BRVO patients without diabetes and in healthy volunteers. The RBF response may differ between subjects with diabetes and those without diabetes.     

Changes in retinal blood flow after application of topical dipivefrine 0.1 %

Hintergrund: Viele der antiglaukomat?sen Medikamente beeinflussen den okul?ren Blutflu?. Die Blutflu?ver?nderungen in der vorderen Uvea sind in der Literatur beschrieben. über den Effekt von Antiglaukomatosa auf den Blutflu? des hinteren Augenpols wird in neuerer Zeit vermehrt berichtet. Wir pr?sentieren eine Placebo-kontrollierte Studie mit Blick auf den kurz- und mittelfristigen Einflu? von topisch appliziertem Dipivefrin 0,1 % auf den retinalen und papill?ren Blutflu?.     

Changes in retinal blood flow after application of topical dipivefrine 0.1 %

PURPOSE: Most of the antiglaucomatous drugs affect ocular blood flow. Blood flow of the anterior uvea under the effect of glaucoma medication has been described in the literature, but measurement of microcirculation at the posterior pole correlated to glaucoma medication is rarely found. We present a placebo-controlled study in which we focused on the short and long-term effects of topical dipivefrine 0.1% on the microcirculation of the retina and optic nerve head. PATIENTS AND METHODS: In a randomized, placebo-controlled double-masked study we examined 40 healthy persons (21 male and 19 female) with a mean age of 35 +/- 4.6 years. Two groups of volunteers (n = 20) were treated either with placebo or dipivefrine 0.1% for 5 days twice a day. Measurement of microcirculation was done at baseline, 30 min after the first application and on days 3 and 5. Microcirculation was evaluated by scanning-laser Doppler flowmetry (SLDF, Heidelberg Engineering; Heidelberg, Germany) [retinal and optic nerve head capillary blood flow (ONH)]. Systemic parameters were checked at all times of blood flow measurement (blood pressure, pulse); intraocular pressure (IOP) was also measured at baseline, 30 min after and on days 3 and 5. RESULTS: Systemic parameters: None of serum medications affected blood pressure or pulse. Dipivefrine 0.1% lowered the IOP significantly (P = 0.01). Microcirculation: dipivefrine 0.1% leads to a significant reduction of retinal capillary blood flow (P = 0.01). ONH blood flow was not significantly affected by dipivefrine 0.1%. CONCLUSION: Retinal capillary perfusion is affected by dipivefrine 0.1% medication. In neuroprotection, it is of interest that glaucoma medication did not alter the microcirculation in a way that leads to an increase of hypoxemia. Therefore, we consider dipivefrine 0.1% not to be useful for long-term glaucoma treatment.     

Abnormal blood rheology in retinal vein occlusion

Hemorheological factors were studied in 34 patients affected by retinal vein occlusion (RVO) and in 25 control subjects. Whole blood viscosity, plasma viscosity, fibrinogen and hematocrit were increased in RVO patients compared with controls. Whole-blood filterability was reduced in RVO patients compared with controls. However, when evaluating the type of capillaropathy at fluorescein angiography, blood viscosity and plasma viscosity were altered in both patients with and without evidence of capillary nonperfusion. Reduction of blood filterability showed statistical significance only in patients with capillary nonperfusion. This finding suggests that reduced whole-blood filterability might be a causal factor in the development of capillary nonperfusion in RVO patients.Presented at the 1984 meeting of the Club Jules Gonin in Lausanne, Switzerland     

Effect of arteriovenous sheathotomy on retinal blood flow and macular edema in patients with branch retinal vein occlusion

PURPOSE: To determine the effect of arteriovenous sheathotomy on retinal blood flow (RBF) in eyes with branch retinal vein occlusion (BRVO). DESIGN: Interventional case series. METHODS: Seven eyes of 7 patients with BRVO underwent sheathotomy and were followed for more than 6 months. RESULTS: At 1 week postoperatively, the RBF in the affected vessels was significantly improved from 14.1 +/- 5.7 to 27.3 +/- 11.3 pixel(2)/sec (P < 0.01), and the foveal thickness (FT) was significantly reduced from 536 +/- 84 to 366 +/- 134 microm (P = 0.03). However, the RBF was reduced again to 11.7 +/- 7.7 pixel(2)/sec at 1 month postoperatively, and the FT was increased to 424 +/- 184 microm. CONCLUSIONS: Arteriovenous sheathotomy led to a transient improvement of the RBF and was effective in reducing macular edema. It is not clear whether the transient effect of sheathotomy affects the long-term visual acuity and macular edema.     

Microvascular changes in experimental branch retinal vein occlusion

Collateral vessel maturation and regional capillary nonperfusion were examined clinically and histopathologically up to 48 months after branch retinal vein occlusion (BVO) in a monkey model. Significant increases in endothelial density, but not pericyte density, were noted in both dilated and normal capillary caliber vessels in regions of collateral flow, independent of duration of BVO from 4 to 15 1/2 months. Patent capillaries in regions of hypoperfusion showed increased endothelial densities but decreased pericyte densities. Pericyte loss was independent of duration of BVO; however, endothelial density may normalize years after BVO in these vessels.     

Central retinal vein occlusion with further reduction of retinal blood flow one year after radial optic neurotomy

PURPOSE: To report a case of central retinal vein occlusion (CRVO) that had vitrectomy with radial optic neurotomy (RON), but the retinal blood flow (RBF) was still reduced 1 year later. DESIGN: Interventional case report. METHODS: An 80-year-old woman had undergone vitrectomy and RON for a CRVO. She had a complete ophthalmic examination, including the RBF analysis using the dye dilution method before and after RON. RESULTS: Seven months after RON, her visual acuity improved from 20/50 to 20/25, and her foveal thickness was decreased from 733 to 213 microm. Indocyanine green angiography demonstrated chorioretinal anastomoses. At 1 year postoperatively, the RBF was reduced from 23.2 to 18 0.1 pixel(2)/s, and the foveal thickness was increased to 767 microm. Her visual acuity decreased to 20/100. The chorioretinal anastomoses were still patent. CONCLUSIONS: These results demonstrate that a further reduction of RBF can occur after RON, and blood flow in the chorioretinal anastomoses may be insufficient to prevent the event.     

Cystoid macular degeneration in experimental branch retinal vein occlusion

Macular edema and collateral vessels were examined clinically and histopathologically up to 48 months after branch retinal vein occlusion in six eyes of five cynomolgus monkeys. In all six, central macular swelling and fluorescein leakage from the retinal vasculature were confined to the acute stage. However, histopathologically, at the chronic stage, only two maculas were completely recovered and unremarkable, whereas the other four showed variable degrees of cystoid degeneration and photoreceptor cell loss. In the two recovered maculas, six to eight normal-sized capillaries separated the fovea from the nearest cluster of capillary collaterals. In three maculas with cystic degeneration, collaterals incorporated the circumfoveal capillaries. In the fourth macula with cystic degeneration, collaterals were separated from the center by two normal-sized capillaries but were also associated with large areas of capillary nonperfusion partially due to occlusion of the macular arteriole.     

视网膜电图明视负向反应在视网膜静脉阻塞中的变化

目的 观察视网膜静脉阻塞(RVO)患者视网膜电图(ERG)明视负向反应(PhNR)的变化特点.方法 对间接检眼镜、荧光素眼底血管造影(FFA)检查确诊的RVO患者30例30只患眼以及对侧健康眼进行视力、视野、闪光ERG(FERG)检查,同时选取与其性别、年龄相匹配的正常人25例50只眼作为正常组进行FERG检查.所有检查均按常规方法进行.RVO患者中,视网膜中央静脉阻塞(CRVO)患者14例14只眼、视网膜分支静脉阻塞(BRVO)患者16例16只眼.根据其病史及FFA检查结果,将其按病程时间划分为小于1个月、1～3个月、大于3个月组;另外再根据RVO分型标准及具体检查结果,将RVO患者分为缺血型和非缺血型.对比分析RVO患眼与对侧健康眼以及正常眼PhNR振幅变化及ERG其他参数指标,包括振荡电位(Ops),视锥细胞反应(Cone-a、Cone-b),视杆细胞反应(Rod-b),暗适应眼的最大反应(Max-a、Max-b),30 Hz闪烁光反应(30 Hz)的差异以及PhNR振幅变化与RVO疾病缺血类型、病程的关系.结果 PhNR振幅在CRVO患眼为(28.20±5.80)μV,BRVO患眼为(36.96±4.71)μV,对侧健眼为(61.25±3.93)μV,正常眼为(59.33±16.92)μV.CRVO组与对侧健眼、正常组比较,差异有统计学意义(F=10.69,9.80;P＜0.001),BRVO组与对侧健眼、正常组比较,差异有统计学意义(F=9.69,9.75;P＜0.001).CRVO组中缺血型PhNR值为(22.77±5.73)μV,非缺血型为(36.63±12.91)μV,二者差异有统计学意义(t=6.54,P＜0.01);BRVO组缺血型PhNR值为(32.39±13.22)μV,非缺血型为(46.73±10.43)μV,二者差异无统计学意义(t=2.12,P＜0.05);病程小于1个月组CRVO与BRVO分别为(24.58±4.60)、(27.94±15.73)μV,1～3个月组分别为(50.39±13.80)、(58.69±12.43)μV,大于3个月组为(25.40±19.94)、(34.48±16.72)μV,CRVO中1～3个月组与大于3个月组差异有统计学意义(F=4.30,P＜0.01).结论 RVO患眼的PhNR振幅较对侧健康眼以及正常对照眼明显降低,缺血型较非缺血型降低,随病程变化呈现下降、上升、下降的变化趋势.