Measurement of venous outflow pressure in the central retinal vein to evaluate intraorbital pressure in Graves' ophthalmopathy: a preliminary report

PURPOSE

To evaluate the intraorbital pressure in patients with Graves' ophthalmopathy (GO) in relation to the intraocular pressure (IOP) and proptosis and to find out whether optic nerve compression is predictable.

METHODS

The venous outflow pressure (VOP) in the central retinal vein was measured by the perviously described technique of oculodynamometry.1 Since the central retinal vein passes through the orbit, the VOP cannot be lower than the intraorbital pressure if outflow is to be guaranteed. The IOP was measured either in primary position or with slight chin elevation to avoid restriction of the globe. Fifty-seven patients underwent a complete ophthalmologic examination, including VOP measurements, Hertel exophthalmometry and visual fields.

RESULTS

The IOP in primary position ranged between 10 and 29 mmHg and in most (n=54) cases the VOP was 0-4 mmHg higher than the IOP. These patients had neither scotomas nor visual deterioration during an observation period of up to 2 years. In those cases (n=3) where the difference between IOP and VOP was 35 mmHg, the patients developed scotomas and visual deterioration and had to be treated (high-dose steroids or orbital decompression). The elevation in VOP did not correlate with the degree of proptosis. In one unilateral case, treatment of high IOP (32 mmHg) with dorzolamide drops led to a decrease in visual acuity of two lines, inferior field depression and relative afferent pupillary defect. The difference between IOP and VOP was 10 mmHg. Stopping treatment normalized visual function, the IOP rose to its original level and the difference between IOP and VOP was 4 mmHg.

CONCLUSION

The increased IOP in GO is not caused by primary glaucoma but by elevated intraorbital pressure. The difference between IOP and VOP must be <5 mmHg to guarantee normal perfusion. We interpret these findings to suggest that loss of visual acuity and visual field defects may not only be caused by optic nerve compression at the apex but also by deterioration of optic nerve head perfusion.

Venous opthalmodynamometry: a noninvasive method for assessment of intracranial pressure

OBJECT

The goal of this study was to examine the potential use of ophthalmodynamometry in the noninvasive assessment of intracranial pressure (ICP). Under normal conditions, pressure within the central retinal vein is equal to or greater than ICP, because the central retinal vein basses through the optic nerve before it drains into the cavernous sinus. The optic nerve sheath is the place where ICP affects retinal venous pressure. Suction ophthalmodynamometry is an established method of investigation in ophthalmology to determine the pressure of the central retinal artery. Although observations of papilledema and lack of venous pulsations are commonly used to provide a vague assessment of ICP, ophthalmodynamometry may be used to determine the pressure of the central retinal vein. This venous pressure has never been compared with ICP.

METHODS

In this study the pressure of the central retinal vein was recorded in 22 patients who underwent continuous simultaneous registration of ICP for various reasons, mainly for suspected hydrocephalus. A comparison of the two pressures was made. The results indicated a highly significant linear correlation between central retinal vein pressure and ICP. These results are of great practical value because up-to-date reliable ICP monitoring has only been possible by using invasive means, by placing a probe extradurally or subdurally into the brain parenchyma or a ventricle.

CONCLUSIONS

Ophthalmodynamometry can be relevant for momentary assessment and is not suitable for continuous monitoring. However, this technique can easily be repeated and may be used whenever increased ICP is suspected in a patient suffering from hydrocephalus, brain tumors, or head injury.

Laser treatment and the mechanism of edema reduction in branch retinal vein occlusion

PURPOSE

To test a hypothesis on the physiological mechanism of the disappearance of macular edema after laser treatment. The hypothesis is based on the effect grid laser treatment has on retinal oxygenation and hemodynamics. It predicts that laser-induced reduction of macular edema is associated with shortening and narrowing of retinal vessels in patients with branch retinal vein occlusion (BRVO).

METHODS

The study included 12 subjects, treated with argon laser photocoagulation for BRVO and macular edema. Fundus photographs taken at the time of diagnosis and again after laser treatment, were digitized, and diameter and segment length of retinal vessels was measured using NIH-Image program.

RESULTS

Macular edema disappeared or was dramatically reduced in all cases after laser treatment. The diameter of occluded venules constricted to 0.81+/-0.02 (mean +/- SD, P = 0.019) of the prelaser diameter and adjacent arterioles constricted to 0.78+/-0.01 (P = 0.008). The laser treatment also led to shortening of the affected vessels. The final segment length of the occluded venules was 0.95+/-0.17 (P = 0.005) of the length before treatment. The corresponding value for the adjacent arterioles is 0.95+/-0.14 (P = 0.008). Control arterioles and venules in the same fundus did not change in either length or width.

CONCLUSIONS

These results do not reject the authors' hypothesis that the disappearance of macular edema in BRVO can be explained by the effect the laser photocoagulation has on retinal oxygenation. Increased oxygenation causes vessel constriction and shortening and lower intravascular pressure, which reduces edema formation according to Starling's law.

[Mechanism of optic nerve congestive disk development during acute period of closed craniocerebral injury]

The mechanism of development of congestion on the fundus oculi in acute posttraumatic intraocular hypertension was studied. A total of 410 patients were examined during the acute period of closed craniocerebral injury of different severity. Pressure in the central retinal vein was tentatively measured by transpalpebral compression of the eyeball with monitoring venous pulsation by direct ophthalmoscopy. The presence of spontaneous pulsation of retinal veins was regarded as an indicator of normal intracranial pressure. Analysis of the severity and location of the intracranial focus of injury together with evaluation of pressure in the retinal vein suggest that congestion on the fundus oculi in closed craniocerebral injury is triggered by the reaction of cavernous sinus intramural baroreceptors to a sudden rise of intracranial pressure.

[Effect of stellate ganglion block on human retinal blood flow]

PURPOSE

The effect of stellate ganglion block (SGB) on human retinal blood flow was evaluated.

METHODS

We measured the diameter of the retinal artery and vein, and retinal venous flow rate by laser speckle retinal blood flow meter simultaneously in 11 eyes of 11 normal volunteers.

RESULTS

The reliable data from 9 eyes of 9 person were used for analysis. SGB did not change the blood pressure, heart rate, retinal arterial diameter, or venous diameter. However SGB increased retinal blood velocity significantly from 9.9 +/- 1.6 (mean +/- standard deviation) mm/s to 11.1 +/- 1.5 mm/s (p < 0.01). Intraocular pressure decreased from 12.3 +/- 2.1 (mean +/- standard deviation)mmHg to 9.4 +/- 2.2 mmHg after SGB (p < 0.01). There was no relationship between the change of ocular perfusion pressure and that of retinal venous blood velocity.

CONCLUSION

SGB increased the retinal venous blood velocity without changing the retinal vessel diameter.

A fluorescein angiographic study of branch retinal artery occlusion (BRAO) - the retrograde filling of occluded vessels

BACKGROUND

For assessing the prognosis of a branch retinal artery occlusion (BRAO), examination of the arterial blood flow by fluorescein angiography is necessary.

PATIENTS AND METHODS

In seven patients (mean age: 68.1, youngest 61, oldest 76 years old), with BRAO of varying involvement and extent, the disturbed retinal blood flow was demonstrated by this method. All the patients were subjected to Doppler sonography of the carotid arteries and all had a general medical examination.

RESULTS

The most impressive sign was the retrograde filling of the retinal arterial and/or venous branches from the adjacent retinal vessels and capillaries. In four patients the visual acuity was better after the disappearance of the retinal edema. In one patient the visual field defect slightly decreased at follow-up. This means that not every patient with retrograde filling of dye in BRAO has a bad prognosis in terms of visual function. The extent and duration of the retrograde filling with dye and the arterial or venous passage varied from patient to patient. There was also delayed filling with an increased period of retention in an artery (which is an adverse sign in BRAO), and retrograde filling of the corresponding vein. This latter came from small adjacent veins, but the retrograde filling of an artery came from capillaries or from very small adjacent arterioles. All the patients showed signs of general systemic disease, such as occlusion or the presence of plaques in the carotid artery, absolute arrhythmia, arterial hypertension, patent foramen ovale, diabetes mellitus, hyperuricemia, Factor V mutation, homocysteinemia or coronary heart disease.

CONCLUSION

Retrograde filling of the retinal arterial and/or venous branches means a kind of spontaneous healing compared to a condition with complete permanent obstruction of circulation. It is recommended that fluorescein angiography should be carried out for all patients with BRAO, in order to estimate the prognosis of the vascular occlusion. This is the first published record of consecutive pictures showing the retrograde filling of retinal arteries and/or veins with BRAO. In every patient with a BRAO an extensive medical and neurological examination (including echocardiography and Doppler sonography of the carotid arteries) is essential before planning the treatment.

[Periphlebitis retinae, uveitis and cystoid maculopathy in a patient with multiple sclerosis]

PATIENT

A 44-year-old woman has a history of multiple sclerosis since 20 years. Besides recurrent numbness she had many instances of optic nerve neuritis which has led to a pronounced optic atrophy on her left eye. Additionally, she has developed recurrent iridocyclitis on her right eye. This was the reason why she was referred to our outpatient department for evaluation. Ophthalmic examination revealed an iridocyclitis associated with a multifocal retinal periphlebitis and severe cystoid macular edema in her right eye.

CONCLUSION

Patients with multiple sclerosis develop in approximately 30% of cases retinal periphlebitis which may rarely be associated with anterior uveitis or cystoid macular edema as observed in our patient.

Pathophysiology and hemodynamics of branch retinal vein occlusion

PURPOSE

To describe the pathophysiologic and the hemodynamic changes associated with branch retinal vein occlusion (BRVO) on the basis of selected angiographic observations from a cohort of patients with BRVO and related anomalies of retinal blood flow.

DESIGN

Retrospective, observational case series.

PARTICIPANTS

A total of 250 patients with incipient or manifest BRVO and 5 patients with related anomalies.

METHODS

Color and red-free gray-scale fundus photography and intravenous fluorescein angiography.

MAIN OUTCOME MEASURES

Morphologic signs of disturbed retinal blood flow.

RESULTS

All occlusions occurred at arteriovenous crossing sites where the artery is positioned anterior to the vein. Presumptive precursor abnormalities of blood flow at arteriovenous crossings include turbulence and upstream venous dilation. After the onset of BRVO, the clinical course is determined by the location of the BRVO in relation to the fovea, the extent of the involved venous drainage area, and the collateral drainage capacity from the area with compromised venous drainage to the adjacent areas of intact venous drainage. Collateral maturation occurs over a period of 6 to 24 months after the onset of BRVO, when a transient retinal edema may be seen that has a preponderance for foveal involvement because the perifoveal area has the highest density of preformed collaterals between adjacent venous drainage areas.

CONCLUSIONS

The treatment of BRVO may possibly benefit from a refined angiographic analysis of the process of collateral formation and new treatment methods aimed at accelerating the process of collateral maturation.

The effect of pregnancy on retinal hemodynamics in diabetic versus nondiabetic mothers

PURPOSE

To investigate retinal circulatory changes that occur during the third trimester of pregnancy in diabetic patients and control subjects.

METHODS

Bidirectional laser Doppler velocimetry and monochromatic fundus photography were used to assess the retinal circulation in seven pregnant diabetic patients and 13 age-matched pregnant control subjects. Retinal venous diameter (D), maximum erythrocyte velocity (Vmax), and retinal volumetric blood flow rate (Q) were measured in one eye of each subject during the third trimester of pregnancy (DPREG, VmaxPREG, and QPREG, respectively). These measurements were repeated during the postpartum period for both diabetic patients (11+/-7 weeks postpartum) and control subjects (16+/-6 weeks postpartum; P = .203; DPOST, VmaxPOST, and QPOST).

RESULTS

In control subjects, DPREG was significantly reduced by -4.5%+/-4.4% (mean percent difference +/-1 standard deviation; paired t test, P =.006) relative to DPOST. In diabetic women, DPREG was also significantly reduced by -8.1%+/-3.2% compared with DPOST (P = .001), a change that was significantly larger than that seen in control subjects (unpaired t test; P = .035). Compared with QPOS T, QPREG was reduced by -7.1%+/-14.2% (P = .123), in control subjects. In diabe tic women, QPREG was significantly decreased by -18.4%+/-9.3% compared with QPOST (P = .012). This reduction in QPREG was significantly greater in diabetic patients than in nondiabetic control subjects (unpaired t test, P = .040). No significant differences between VmaxPREG and VmaxPOST were observed in either diabetic patients (-3.1%+/-12.9%; P =.400) or control subjects (+1.9%+/-14.4%; P = .787).

CONCLUSIONS

Retinal venous diameter is decreased during the third trimester of pregnancy in both diabetic and nondiabetic mothers. This decrease is significantly larger in diabetic than in nondiabetic mothers. In addition, we observed a reduction in retinal volumetric blood flow in diabetic patients during pregnancy that was significantly larger than that present in nondiabetic women. This fall in retinal volumetric blood flow in diabetic patients may exacerbate retinal ischemia and hypoxia and thus may be associated with the progression of diabetic retinopathy.

Venous collateral remodeling in a patient with posttraumatic glaucoma

PURPOSE

To photographically document venous collateral development, remodeling, and regression in a patient with traumatic glaucoma.

METHODS

Consecutive fundus photographs were evaluated, labeled, and correlated with the clinical history of a patient with unilateral posttraumatic glaucoma.

RESULTS

This report photographically documents the appearance, remodeling, and subsequent disappearance of collateral vessels from venous occlusion on the surface of the optic disk in an eye with increased intraocular pressure and progressive glaucomatous cupping.

CONCLUSIONS

Asymptomatic chronic obstruction of a branch retinal vein on the optic disk may cause venous collaterals to develop in the absence of retinal hemorrhages or other signs of venous occlusive disease. Increased intraocular pressure, arteriolarsclerosis, and glaucomatous cupping are risk factors for these occlusions.

[Hemodynamics of prepapillary vascular loop in hemi-central retinal vein occlusion]

BACKGROUND

It has been shown, by indocyanine green (ICG) videoangiography, that the prepapillary vascular loops in chronic central retinal vein occlusion (CRVO) serve as an anastomosis between the retina and the choroidal venous systems. Similar vascular loops may develop in hemi-central retinal vein occlusion (hemi-CRVO).

CASES AND METHODS

I performed indocyanine green and fluorescein angiography using a scanning laser ophthalmoscope in 8 eyes of 8 patients with hemi-CRVO to evaluate the angioarchitecture and hemodynamics of the retinochoroidal circulation. All eyes had a prepapillary vascular loop and were identified as ischemic. The patients' ages ranged from 28 to 77 years (mean, 57 years). The interval between onset of hemi-CRVO and angiography ranged from 2 to 42 months (mean, 13 months). Scattered laser photocoagulation had been applied to the affected area in all 8 eyes and vitreous surgery in one eye.

RESULTS

Delayed dye flow in the affected retinal veins was present in all 8 eyes. The blood in the affected retinal veins drained through the prepapillary vascular loop into the branch or trunk of the intact central retinal vein. No anastomoses were seen between the vascular loop and the choroidal veins. The prepapillary vascular loop became more dilated during follow-up in one eye.

CONCLUSIONS

The prepapillary vascular loop in hemi-CRVO served as a collateral from the affected into intact retinal veins and not into the choroidal venous system.

Surgical decompression of branch retinal vein occlusion via arteriovenous crossing sheathotomy: a prospective review of 15 cases

BACKGROUND

Branch retinal vein occlusion (BRVO), the second most common vascular disorder of the retina, typically occurs at arteriovenous (A/V) crossings where the arteriole and venule share a common adventitial sheath. Mechanical narrowing of the venous lumen at these intersections is thought to play a pathoetiologic role in BRVO.

METHODS

We performed surgical decompression of BRVO via A/V crossing sheathotomy in 15 patients with decreased visual acuity due to macular hemorrhage, edema, and ischemia. Reperfusion of the retina was achieved by surgically separating the overlying retinal arteriole from the venule via vitrectomy and adventitial sheathotomy techniques.

RESULTS

Intraoperative decompression of the A/V crossing was achieved in all 15 patients. All patients showed clinical improvement as determined by fundus examination, photography, and fluorescein angiography. Postoperative visual acuities were equal or improved in 80% of patients. Ten of the 15 subjects (67%) had improved visual acuity with an average gain of four lines of vision.

CONCLUSION

Surgical decompression of BRVO via A/V crossing sheathotomy is a technically feasible procedure that can result in rapid reperfusion of the retina. Resolution of macular hemorrhage, edema, and ischemia may improve visual prognosis in patients with this common retinal vascular disorder.

Retinal blood flow measurements in branch retinal vein occlusion using scanning laser Doppler flowmetry

PURPOSE

To determine capillary blood flow measurements in eyes with branch retinal vein occlusion using a scanning laser Doppler flowmeter.

METHODS

Retinal capillary blood flow in branch retinal vein occlusion areas and corresponding ipsilateral nonbranch retinal vein occlusion areas, 11 equivalent areas of the contralateral fellow eye of 12 consecutive untreated branch retinal vein occlusion patients, and 16 eyes of 11 age-matched normal control subjects were measured with scanning laser Doppler flowmetry. A template consisting of eight squares, each with a field of 100 x 100 microm (10 x 10 pixel) with space interval of 500 microm equidistant horizontally and vertically was used to obtain blood flow measurements in all subjects. Mean blood volume, flow, and velocity were obtained by averaging the mean values measured in each field. We avoided measurement over large retinal vessels to prevent the aliasing artifact of blood cells from moving faster than the sampling frequency.

RESULTS

Branch retinal vein occlusion areas have significantly decreased microvascular blood volume (P = .0009), flow (P = .02), and velocity (P = .016) compared with ipsilateral nonbranch retinal vein occlusion areas in the same eye. Branch retinal vein occlusion areas also have decreased blood volume (P = .001), flow (P = .0042), and velocity (P = .0044) compared with areas of contralateral fellow eyes of branch retinal vein occlusion subjects. Branch retinal vein occlusion areas have significantly decreased blood volume (P = .0012), flow (P = .008), and velocity (P = .02) compared with age-matched normal areas.

CONCLUSION

Average retinal blood volume, flow, and velocity in areas of branch retinal vein occlusion are significantly lower than in healthy retinas. The ability to noninvasively measure hemodynamic changes in the retinal capillary bed may be relevant to development of new therapies for retinovascular disease.

Treatment of central retinal vein occlusion by injection of tissue plasminogen activator into a retinal vein

PURPOSE

To report the injection of tissue plasminogen activator into a retinal vein to treat central retinal vein occlusion.

METHODS

An 81-year-old woman with visual loss of the right eye secondary to central retinal vein occlusion developed central retinal vein occlusion and visual loss in her left eye. Treatment of her left eye with topical ocular hypotensive medications, pentoxifylline, and laser chorioretinal anastomosis was without benefit. Thereafter, she underwent vitreoretinal surgery, including tissue plasminogen activator injection into a branch retinal vein of her left eye.

RESULTS

The patient reported subjective improvement in the vision of her left eye. Ophthalmoscopic and fluorescein angiographic improvement were also noted.

CONCLUSION

The feasibility of cannulating a retinal vein for treatment has been demonstrated.

Reversal of blood flow in experimental branch retinal vein occlusion

BACKGROUND AND OBJECTIVE

To demonstrate that the obstructed vascular lumen of the experimentally induced branch retinal vein occlusion (BRVO) induces retrograde blood flow, resulting in flow from the occluded vein to the feeder arterioles.

MATERIALS AND METHODS

Photocoagulation was used to create occlusion of the branch retinal vein in a monkey model (n = 2; 1 cynomolgus, 1 rhesus). Twenty-four hours following photocoagulation, the eyes were examined for evidence of vascular occlusive disease. Vascular occlusion was proven by fluorescent vesicle angiography with scanning laser ophthalmoscopy; these results were recorded to SVHS videotape. The images were then serially analyzed frame by frame to track individual microsphere movement.

RESULTS

The authors observed retrograde flow proximal to the point of vessel obstruction and extending backward into the arterial system.

CONCLUSIONS

This demonstrates the existence of retrograde flow in an experimental model of BRVO and might explain vascular complications seen in this disease process.

Retinal blood flow in nonischemic central retinal vein occlusion

OBJECTIVE

The authors studied the changes in retinal blood flow (RBF) and oxygen reactivity in a major temporal vein in patients with central retinal vein occlusion (CRVO).

PARTICIPANTS

Eleven patients with nonischemic CRVO approximately 7 weeks from onset of disease.

INTERVENTION

Laser Doppler velocimetric measurement of RBF and vessel reactivity to inhaling 60% oxygen. Measurements were performed at baseline and 3 months.

RESULTS

Flow velocity in the affected eye had increased significantly by 3 months, from 1.6 +/- 0.4 cm/second to 2.0 +/- 0.4 cm/second (P = 0.02). Retinal blood flow, however, remained unchanged (13.7 +/- 5.8 microl/minute versus 15.0 +/- 6.5 microl/minute). The two comparable RBF values, despite differing velocity values, suggest that the relatively normal baseline value was achieved through higher intravascular pressure at baseline (Bernoulli's principle). This is supported by the fact that oxygen reactivity had improved from 2.1% +/- 3.6% at baseline to 3.8% +/- 3.1% (P = 0.001) at 3 months, which suggests an improved ability to respond to hyperoxia from reduced intravascular pressure.

CONCLUSION

Intravascular pressure in CRVO appears to continue to decrease during the first 5 months after the onset of CRVO, indicating continuing reduction in the degree of outflow obstruction during this time.

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.

Systemic hyperoxia decreases vascular endothelial growth factor gene expression in ischemic primate retina

OBJECTIVES

To determine whether systemic hyperoxia can reverse retinal hypoxia and decrease vascular endothelial growth factor (VEGF) gene expression in ischemic nonhuman primate retina.

METHODS

Six eyes of 3 cynomolgus monkeys were studied. Retinal ischemia was induced via laser vein occlusion and confirmed with fluorescein angiography. Animals were randomly assigned to treatment with either 21% or 100% inhaled oxygen. Arterial PO2 was monitored while systemic acid-base status was maintained. An oxygen microelectrode on a micromanipulator was used to measure preretinal oxygen concentrations in ischemic and nonischemic retina in situ. RNA was isolated from fresh whole retinas, and VEGF messenger RNA levels were quantified with Northern blotting.

RESULTS

The preretinal PO2 in ischemic retina was less than the PO2 in nonischemic retina in animals breathing 21% oxygen (intervascular zone PO2, 14.3+/-0.53 vs 21.8+/-0.55 mm Hg; P=.002). After 8 hours of systemic hyperoxia (arterial PO2, 512+/-18 mm Hg), the preretinal PO2 in ischemic retina increased to 166.2+/-15.6 mm Hg (21.8% oxygen) and retinal VEGF messenger RNA levels were reduced by an average of 55%.

CONCLUSIONS

These data demonstrate that systemic hyperoxia can lower retinal VEGF gene expression and reoxygenate ischemic adult primate retina.

[Pseudoexfoliation syndrome in patients with retinal vein branch and central vein thrombosis]

BACKGROUND

Pseudoexfoliation syndrome is a frequent cause of secondary open-angle glaucoma due to deposition and in situ-production of abnormal extracellular matrix proteins in the trabecular meshwork. Glaucomas itself are a known risk factor for retinal vein thrombosis. In this retrospective study the prevalence of pseudoexfoliation syndrome in patients with branch and central retinal vein thrombosis was investigated.

PATIENTS AND METHODS

The records of 332 unselected patients with branch retinal vein thrombosis and 159 with central retinal vein thrombosis, which were seen in our laser out-patient clinic between January 1990 and July 1996, were analysed retrospectively.

RESULTS

6.0% of patients with branch and 6.9% of patients with central retinal vein thrombosis revealed pseudoexfoliation syndrome. The full picture of pseudoexfoliation syndrome was seen in 4.2% of patients with branch and in 4.4% of patients with central retinal vein thrombosis. The prevalence of pseudoexfoliation syndrome increased with age. Twenty percent of patients with branch and 27% of patients with pseudoexfoliation syndrome and branch or central retinal vein thrombosis. The branch retinal vein thrombosis was significantly more often localised at the disk in patients with glaucoma and in patients with pseudoexfoliation syndrome.

CONCLUSIONS

Pseudoexfoliation syndrome is a risk factor for retinal vein thrombosis. Pathogenetically the secondary open-angle glaucoma caused by pseudoexfoliation syndrome could be causative for the venous thrombosis.

Increased vascular resistance for venous outflow in central retinal vein occlusion

PURPOSE

The authors quantified the vascular resistance for venous outflow in central retinal vein occlusion (CRVO).

METHODS

The blood velocity in the central retinal vein (CRV) and central retinal artery (CRA) was measured by pulsed Doppler sonography (4-Mhz probe), and the pulse curve of the intraocular pressure (IOP) was evaluated by pneumotonometry. With multichannel data acquisition and storage software, the velocity-pulse curve of the CRV and CRA, the IOP-pulse curve, the arterial blood pressure, and the electrocardiogram were measured simultaneously in real-time mode. The relationships between the pulse curves of the blood velocity in the CRV and CRA and the IOP were calculated off-line. The onset time, the time of half maximum, and the time to the maximum of the pulse curves were evaluated. A relative index R' for the retinal outflow resistance was calculated by R' = deltaIOP/deltaVcrv. The authors examined 23 eyes of 23 patients with CRVO not older than 2 weeks and 23 eyes of 23 age-matched controls. There was no significant difference between the mean age of the control group (46 +/- 16 years) and that of the CRVO group (54 +/- 20 years).

RESULTS

In eyes with CRVO, the authors found significantly lower systolic, diastolic, and mean outflow velocity. The amplitude of the CRV velocity pulse was significantly decreased compared with control eyes. In CRVO, the mean CRV velocity pulse amplitude (deltaVvein) was 1.77 +/- 1.0 cm/second, and in controls, it was 2.08 +/- 0.61 cm/second (P < 0.005). There was no significant difference in the mean IOP, but the IOP pulse amplitude (deltaIOP) was significantly higher in CRVO compared with controls (deltaIOP: CRVO 2.82 +/- 1.45 mmHg, control 1.96 +/- 0.56 mmHg, P < 0.005). The relative resistance index R' for venous outflow was significantly increased in eyes with CRVO (2.0 +/- 1.1 mmHg/cm/sec) compared with controls (1.1 +/- 0.44 mmHg/cm/s, P < 0.001).

CONCLUSION

In eyes with CRVO, the systolic, diastolic, and mean velocity and the amplitude of the CRV velocity-pulse curve were significantly decreased and the resistance for retinal venous outflow was significantly increased compared with controls.

[Color-coded duplex ultrasonography of the orbit in central vein thrombosis]

PURPOSE

To evaluate the haemodynamic findings of orbital vessels in patients with central retinal vein occlusion by colour coded duplex sonography.

METHODS

In 24 patients suffering from central retinal vein occlusion, confirmed by ophthalmoscopy and fluorescence angiography, colour-coded duplex sonography of central retinal vein, central retinal artery, posterior ciliary arteries and ophthalmic artery of the affected, and the unaffected contralateral eye, was performed and compared to a control group (150 healthy subjects).

RESULTS

In eyes with central retinal vein occlusion, the maximum velocity of the central retinal vein was on average 4.55 cm/s (+/-2.37 cm/s) and, as compared with the unaffected eye (mean: 6.56 +/- 1.47 cm/s) and the control group (5.97 +/- 2.37 cm/s), reduced significantly. In the affected eyes, the end diastolic velocity of the central retinal artery was reduced and the pulsatility index was increased significantly, compared with the unaffected eyes and the control group. Compared with the control group, the peak systolic and end diastolic velocities of the ophthalmic artery were significantly reduced.

CONCLUSION

In conclusion, the findings assessed by colour-coded duplex sonography show a flow reduction in the central retinal vein and an increased arterial flow resistance in the retinal layer. There is good correlation with the angiographic results. Moreover, flow reductions in the ophthalmic artery, which are not seen in ophthalmological examinations, can be detected by this new examination technique.

Electroretinography of central retinal vein occlusion under scotopic and photopic conditions: what to measure?

INTRODUCTION

In the management of cases of central retinal vein occlusion it is important to identify those patients who will develop the complication of iris neovascularisation. Electroretinography is of proven use in this role but there is some confusion about which parameters to measure and at what stimulus intensities.

METHODS

A variety of ERG parameters in scotopic and photopic conditions were tested by ROC analysis for the prediction of the development of this complication in 39 patients with CRVO.

RESULTS

The results indicated that a single flash and measurement of the b/a ratio under photopic conditions is as effective in this aim as measuring multiple parameters.

CONCLUSION

A simplified and shortened protocol could be used in the examination of this condition thereby making the application of ERG more practical in the clinical setting.

Blood flow velocity in the extraocular vessels in chronic smokers

AIMS

To determine blood flow velocity in the extraocular vessels in healthy, chronic smokers and to compare these blood flow velocities with those of healthy non-smokers.

METHODS

In 46 healthy chronic smokers and 189 healthy non-smokers, peak systolic velocity (PSV), end diastolic velocity (EDV), and the resistivity index (RI) were measured in the ophthalmic artery (OA), central retinal artery (CRA), lateral short posterior ciliary artery (LPCA), and medial short posterior ciliary artery (MPCA) by means of a colour Doppler device, Siemens Quantum 2000. The maximal (max) and minimal (min) velocities were measured in the central retinal vein (CRV). Only one eye was measured in each subject, and right and left eyes were chosen randomly. Blood flow velocities were compared with one way MANOVA and t tests. The influence of age, sex, systolic and diastolic blood pressure, as well as heart rate on blood flow velocity and RI were evaluated by an analysis of covariance. The potential differences of the influence of the covariables on blood flow variables in smokers and non-smokers were tested by calculating the interactions.

RESULTS

In the majority of measured vessels blood flow velocity was higher in smokers than in non-smokers. This difference was statistically significant in the OA, CRV, and LPCA. The RI indices were equal or slightly lower in smokers. Furthermore, smokers had significantly lower systolic and diastolic blood pressure. Heart rate was higher in smokers but this difference did not reach statistical significance.

CONCLUSIONS

Colour Doppler measurements may differ significantly in smokers compared with non-smokers. Therefore, smoking habits should be considered when interpreting colour Doppler imaging results, and comparing different groups of diseased or healthy subjects.