Retinal perfusion response to a slow multifocal M-sequence flicker stimulation

PURPOSE

To assess, if a slow multifocal stimulus (mfS) can provoke a perfusion response that can be measured with the Retinal Vessel Analyzer (RVA).

METHODS

Seventeen eyes were examined. Pupils were dilated. A 120-second baseline recording was obtained with the RVA. The subject then turned to view an mfS for 56 s. The mfS consisted of 103 hexagons flickering according to an m-sequence with a stimulus base interval of 53.3 ms (L(max) = 100 cd/m(2), L(min) < 1 cd/m(2)). Immediately thereafter, the subject turned to the RVA, where measurements were resumed as soon as the same retinal vessel was targeted and continued for 104 s. Stimulation and recording was repeated twice. The diameter of a retinal vein and artery was measured for a length of at least 1 mm. The maximum vessel response was obtained by linear interpolation of the measured response within the 20 s following mfS.

RESULTS

On average, veins dilated by 6.8% and arteries by 7% following mfS (p > 0.005). Such a dilatation could be observed in 9 veins and 7 arteries. Three venous and 2 arterial measurements did not show a dilatation following mfS. However, 13 of 34 measurements could not be analyzed due to signal problems or because the time from the end of mfS and the uptake of measurement exceeded 20 s.

CONCLUSION

This slow multifocal ERG stimulus results in a dilatation of arteries and veins that can be measured with the RVA. Coupling an mfS to the RVA has the potential to topographically map changes in retinal perfusion in relation to the respective retinal area stimulated. When implementing the mfS into the RVA setup in order not to lose time due to the refixation in the RVA following mfS, one is required to take the transient nature of this perfusion change into consideration.

Effect of retrobulbar versus subconjunctival anaesthesia on retrobulbar haemodynamics

AIM

To investigate the effect of retrobulbar and subconjunctival anaesthesia on retrobulbar haemodynamics by colour Doppler imaging.

METHOD

39 patients (mean age 71 (SD 9) years; 19 females, 20 males) undergoing planned cataract surgery were included in the prospective study. Colour Doppler imaging (Siemens Sonoline Sienna, Germany) was performed before, directly after either subconjunctival (16 patients) or retrobulbar (23 patients) anaesthesia, and after cataract surgery to measure the peak systolic (PSV) and end diastolic velocities (EDV) in the ophthalmic artery (OA), central retinal artery (CRA), and central retinal vein (CRV).

RESULTS

After retrobulbar anaesthesia there was a significant reduction of the PSV and of the EDV in all investigated vessels. After surgery the flow velocities increased again. Subconjunctival anaesthesia had no significant effects on retrobulbar haemodynamics.

CONCLUSION

Retrobulbar anaesthesia induces a high reduction of velocity in the retrobulbar vessels in contrast with subconjunctival anaesthesia. Therefore subconjunctival anaesthesia should be preferred particularly in patients with problems of the ocular perfusion (for example, glaucoma).

Response of retinal vessel diameters to flicker stimulation in patients with early open angle glaucoma

INTRODUCTION

Diffuse luminance flicker increases retinal vessel diameters in animals and humans, indicating the ability of the retina to adapt to different metabolic demands. The current study seeks to clarify whether flicker-induced vasodilatation of retinal vessels is diminished in glaucoma patients.

METHODS

Thirty-one patients with early stage glaucoma (washout for antiglaucoma medication) and 31 age- and sex- matched healthy volunteers were included in the study. Retinal vessel diameters were measured continuously with a Retinal Vessel Analyzer. During these measurements three episodes of square wave flicker stimulation periods (16, 32, and 64 secs; 8 Hz) were applied through the illumination pathway of the retinal vessel analyser.

RESULTS

Flicker-induced vasodilatation in retinal veins was significantly diminished in glaucoma patients as compared with healthy volunteers (ANOVA, P < 0.01). In healthy volunteers, retinal venous vessel diameters increased by 1.1 +/- 1.8% (16 seconds, P < 0.001), 2.0 +/- 2.6 (32 seconds, P < 0.001), and 2.1 +/- 2.1% (64 seconds, P < 0.001) during flicker stimulation. In glaucoma patients, venous vessel diameters increased by 0.2 +/- 1.7% (16 seconds, P < 0.6), 1.1 +/- 2.1% (32 seconds, P < 0.01), and 0.8 +/- 2.5 (64 seconds, P < 0.09). In retinal arteries, no significant difference in flicker response was noticed between the two groups (ANOVA, P < 0.6). In healthy controls, flicker stimulation increased retinal arterial vessel diameters by 1.0 +/- 2.4% (P < 0.03), 1.6 +/-3.2% (P < 0.004) and 2.4 +/- 2.6% (P < 0.001) during 16, 32, and 64 seconds of flicker, respectively. In glaucoma patients, flickering light changed arterial vessel diameters by 0.3 +/-2.6% (16 seconds, P = 0.4), 1.3 +/-3.1% (32 seconds, P = 0.03), and 1.8 +/- 3.8% (64 seconds, P = 0.005).

CONCLUSION

Flicker-induced vasodilatation of retinal veins is significantly diminished in patients with glaucoma compared with healthy volunteers. This indicates that regulation of retinal vascular tone is impaired in patients with early glaucoma, independently of antiglaucoma medication.

Reduced response of retinal vessel diameters to flicker stimulation in patients with diabetes

BACKGROUND/AIM

Stimulation of the retina with flickering light increases retinal arterial and venous diameters in animals and humans, indicating a tight coupling between neural activity and blood flow. The aim of the present study was to investigate whether this response is altered in patients with insulin dependent diabetes mellitus.

METHODS

26 patients with diabetes mellitus with no or mild non-proliferative retinopathy and 26 age and sex matched healthy volunteers were included in the study. Retinal vessel diameters were measured continuously with the Zeiss retinal vessel analyser. During these measurements three episodes of square wave flicker stimulation periods (16, 32, and 64 seconds; 8 Hz) were applied through the illumination pathway of the vessel analyser.

RESULTS

In retinal arteries, the response to stimulation with diffuse luminance flicker was significantly diminished in diabetic patients compared to healthy volunteers (ANOVA, p<0.0031). In non-diabetic controls flicker stimulation increased retinal arterial diameters by +1.6% (1.8%) (mean, p<0.001 v baseline), +2.8% (SD 2.2%) (p<0.001) and +2.8% (1.6%) (p<0.001) during 16, 32, and 64 seconds of flicker stimulation, respectively. In diabetic patients flicker had no effect on arterial vessel diameters: +0.1% (3.1%) (16 seconds, p = 0.9), +1.1% (2.7%) (32 seconds, p = 0.07), +1.0% (2.8%) (64 seconds, p = 0.1). In retinal veins, the response to flicker light was not significantly different in both groups. Retinal venous vessel diameters increased by +0.7% (1.6%) (16 seconds, p<0.05), +1.9% (2.3%) (32 seconds, p<0.001) and 1.7% (1.8%) (64 seconds, p<0.001) in controls during flicker stimulation. Again, no increase was observed in the patients group: +0.6% (2.4%), +0.5% (1.5%), and +1.2% (3.1%) (16, 32, and 64 seconds, respectively).

CONCLUSION

Flicker responses of retinal arteries and veins are abnormally reduced in patients with IDDM with no or mild non-proliferative retinopathy. Whether this diminished response can be attributed to altered retinal vascular reactivity or to decreased neural activity has yet to be clarified.

Ophthalmodynamometric determination of the central retinal vessel collapse pressure correlated with systemic blood pressure

AIMS

To evaluate whether determination of the central retinal artery and vein collapse pressure correlate with systemic blood pressure measurements, using a new Goldmann contact lens associated ophthalmodynamometric device

METHODS

The prospective clinical study included 92 eyes of 92 patients presenting with cataract or refractive problems (n = 40; control study group) or with retinal and orbital pathologies (n = 52). With topical anaesthesia, a Goldmann contact lens fitted with a pressure sensor in its holding ring was placed onto the cornea. Pressure was asserted onto the globe by pressing the contact lens, and the pressure value at the time when the central retinal artery and vein started pulsating were noted as central retinal artery and vein collapse pressure. Additionally, the brachial arterial blood pressure was measured.

RESULTS

In the control study group, central retinal artery collapse pressure was highly significantly correlated with diastolic blood pressure (correlation coefficient r = 0.77; p<0.001) and systolic blood pressure (r = 0.35; p = 0.03). Central retinal vein collapse pressure was statistically independent of diastolic blood pressure (p = 0.11). In eyes with retinal or orbital diseases, the correlation coefficients were lower than in the control study group. In eyes with retinal arterial occlusions, central retinal vessel collapse pressure measurements were not correlated with arterial blood pressure measurements.

CONCLUSIONS

Depending on coexisting retinal or orbital diseases, ophthalmodynamometric estimation of the central retinal artery collapse pressure, performed during a routine Goldmann contact lens ophthalmoscopy, correlates with systemic blood pressure measurements.

Retinal Vessel Diameters and Their Associations with Age and Blood Pressure

PURPOSE

To describe the cross-sectional relationship between retinal arteriolar and venular diameters with age and blood pressure.

METHODS

A population-based study was conducted in Beaver Dam, Wisconsin (n=4926, age range, 43-84 years). Retinal photographs of right eyes taken at the baseline examination (1988-90) were digitized. All arterioles and venules located in the area between one-half and one disc diameter from the optic disc margin were measured with a computer-based program. These measurements were combined to provide the average diameters of retinal arterioles and venules of each eye, and the association with age and blood pressure (BP) was analyzed.

RESULTS

After controlling for gender, hypertension, diabetes, serum glucose and lipids, cigarette smoking, and body mass index, retinal arteriolar diameters were found to be decreased by 2.1 microm (95% confidence interval [CI], 1.5-2.7) for each decade increase in age, and by 4.4 microm (95% CI, 3.8-5.0) for each 10-mm Hg increase in mean arterial BP. The association of narrowed retinal arterioles and higher BP was stronger in younger persons. For each 10-mm Hg increase in mean arterial BP, arteriolar diameters decreased by 7.0 microm in persons aged 43 to 54 years but by only 2.5 microm in persons aged 75 to 84 years. In contrast, retinal venular diameters narrowed with increasing age but not with increasing BP.

CONCLUSIONS

Retinal arteriolar diameters are narrower in older persons and in persons with higher BP, independent of other factors. The weaker association of retinal arteriolar diameters and BP in older people may reflect greater sclerosis of the retinal arterioles, preventing a degree of narrowing with higher BP similar to that seen in younger persons.

Central retinal artery and vein collapse pressure in eyes with chronic open angle glaucoma

AIMS

To determine central retinal vessel collapse pressure in chronic open angle glaucoma.

METHODS

For 19 eyes with chronic open angle glaucoma and 27 eyes of a control group, central retinal vessel collapse pressure was measured by a Goldmann contact lens fitted with a pressure sensor in its holding grip.

RESULTS

Central retinal vein collapse pressure was significantly (p=0.001) higher in the glaucoma group than in the control group (26.1 (SD 26.4) relative units versus 6.1 (8.4) relative units).

CONCLUSIONS

Measured by a new ophthalmodynamometer, central retinal vein collapse pressure measurements may be abnormally high in eyes with chronic open angle glaucoma.

Ophthalmodynamometry in eyes with dilated episcleral veins

PURPOSE

To determine the central retinal vessel collapse pressure in patients with dilated episcleral veins.

METHODS

This clinical noninterventional comparative study included a study group of 10 eyes (6 patients) with dilated episcleral veins, and a control group consisting of 50 eyes of 40 patients with cataract or refractive problems. With topical anesthesia, a Goldmann contact lens fitted with a pressure sensor in its holding ring was placed onto the cornea. Pressure was asserted onto the globe by pressing the contact lens, and the pressure value at the time when the central retinal artery and vein started pulsating was noted as central retinal artery and vein collapse pressure.

RESULTS

Central retinal vein collapse pressure was significantly higher (P<0.001) in the study group with dilated episcleral veins than in the control group (37.9 +/- 33.8 vs 5.1 +/- 8.4 relative units [RU]). In the central retinal artery, there was not significant difference in diastolic collapse pressure measured between the study and control groups (78.2 +/- 22.8 vs 74.2 +/- 18.8 RU, respectively; P = 0.74).

CONCLUSIONS

As measured by a new ophthalmodynamometer with biomicroscopic visualization of the central retinal vessels during the examination, the central retinal vein collapse pressure measurements were significantly higher in eyes with dilated episcleral veins than in control eyes. Ophthalmodynamometric estimation of the central retinal vein collapse pressure may be helpful in the assessment of patients with dilated episcleral veins.

Management of central retinal vein occlusion

The management of central retinal vein occlusion (CRVO) is discussed briefly. Since the prognosis, complications, visual outcome and management of nonischemic and ischemic CRVO are very different, the first essential step in the management of CRVO is to determine which type of CRVO one is dealing with. The various parameters which help to differentiate the two types reliably are described briefly. In this connection, the most important thing to remember is that the conventional, very prevalent use of a 10-disc area of retinal capillary obliteration is an invalid parameter to differentiate ischemic from nonischemic CRVO, or to predict ocular neovascularization (NV). Ocular NV is a complication of ischemic CRVO only. Relevant issues about the natural history of CRVO are summarized; the natural history of the disease must not be mistaken for a beneficial effect of treatment. Various advocated modes of treatment of CRVO and their relative merits are discussed, particularly photocoagulation, which is widely advocated. Controversies with regard to various aspects of CRVO management are examined. Finally, it is noted that apart from routine systemic and hematologic evaluations, the vast majority of patients with CRVO do not need an extensive and expensive workup. In conclusion, in spite of enthusiastic claims of success for various therapies, the reality is that we currently have practically no proven safe and effective treatment for CRVO.

Relation between retrobulbar circulation and progression of diabetic retinopathy

AIMS

To investigate retrobulbar circulatory parameters in type 2 diabetic patients with and without diabetic retinopathy (DR) progression.

METHODS

This was a prospective cohort study. One eye of 35 diabetic patients with background DR (BDR) were included in the study. Eyes without DR, with proliferative DR, photocoagulation, past surgical procedures, or other ophthalmic disease except BDR and cataract were excluded. The study was masked. Colour Doppler imaging (CDI) was used to measure the retrobulbar circulation at the beginning of the study and after a mean follow up interval of 21 months. Peak systolic velocity (PSV), end diastolic velocity (EDV), and resistivity index (RI) in the central retinal artery and vein and the posterior ciliary artery were measured.

RESULTS

18 patients who developed DR progression showed significantly increased central retinal vein PSV ( 5.6 (3.5-9.1) p = 0.003), EDV ( 3.4 (2.3-4.4) p = 0.04), and RI ( 0.43 (0.20-0.56) p = 0.02) at the final measurement compared to the initial measurement (PSV = 4.6 (3.2-7.0); EDV = 3.0 (2.3-3.7); RI = 0.40 (0.17-0.52)). Circulatory parameters in the central retinal artery and the posterior ciliary artery did not alter significantly after progression of DR. 17 patients were without DR progression and they did not show any significant differences in the measured circulatory parameters on entry compared to the final measurement.

CONCLUSION

The authors suggest that the initial changes in the retrobulbar circulation during DR progression occur in the central retinal vein.

Reproducibility of ophthalmodynamometric measurements of central retinal artery and vein collapse pressure

BACKGROUND

To assess the reproducibility of ophthalmodynamometric measurements using a new, Goldmann contact lens associated, device allowing biomicroscopic visualisation of the optic disc.

METHODS

The prospective clinical study included 87 eyes of 58 subjects presenting with a normal fundus (n=40), or ocular diseases (n=47). With topical anaesthesia, a Goldmann contact lens, fitted with a pressure sensor mounted into the holding ring of the contact lens, was placed onto the cornea. Pressure was applied onto the globe through the contact lens, and the pressure values obtained when the central retinal vessels started pulsating were noted. The measurements were performed 10 times.

RESULTS

The mean coefficients of variation for redeterminations of the collapse pressure of the central retinal vein and artery were 16.3% (SD 11.4%), and 8.5% (4.1%), respectively.

CONCLUSIONS

A simple and new, Goldmann contact lens associated, ophthalmodynamometer allows central retinal artery and vein collapse pressure measurements which are reproducible in a clinical setting.

Extraocular blood flow and endothelin-1 plasma levels in patients with multiple sclerosis

In order to evaluate whether plasma levels of the potent vasoconstrictor endothelin-1 (ET-1) are increased in patients with multiple sclerosis (MS) and whether these patients exhibit an ET-1-mediated vascular dysregulation, ET-1 plasma levels were measured in 30 patients with MS. Blood flow velocities in the ophthalmic artery, central retinal artery, central retinal vein, short lateral posterior ciliary artery, and short medial posterior ciliary artery were assessed in parallel. ET-1 plasma levels were significantly increased in MS patients when compared to sex- and age-matched healthy controls (2.0 +/- 0.4 pg/ml, range 1.1-2.8 vs. 1.5 +/- 0.2 pg/ml, range 0.9-2.0; p < 0.001). Moreover, the patients exhibited significant alterations of extraocular blood flow. The role of ET-1 in the inflammatory process remains to be clarified.

Comparison of venous filling times and SLO findings at each quadrant region in diabetic retinopathy

Our purpose is to evaluate the correlation of retinal venous filling time (VFT), which reflects the peripheral retinal microcirculation in diabetic retinopathy, with fluorescein angiography (FAG) findings such as microaneurysm (MA), non-perfusion area (NP), neovascularization (NV) and relative retinal venous diameter (RRVD), and further, to evaluate the correlation between arteriovenous passage time (AVPT) and these factors. Partial F-test (multiple regression analysis) was performed on patients (32 eyes of diabetic retinopathy) who underwent video FAG, using scanning laser ophthalmoscope. In the four quadrants, VFT was compared with each MA, NP, and NV at each vascular arch at a distance of one disc diameter distant from the optic disc. VFT was significantly correlated to RRVD, NP, and NV at each quadrant (r > 0.7). However, AVPT was not significantly correlated to any of the factors studied. Delayed VFT was associated with the hemodynamic change of the peripheral retinal microcirculation at each quadrant in diabetic retinopathy. VFT can be used as an index to indicate the peripheral microcirculation of the retina.

Spontaneous retinal venous pulsation: aetiology and significance

Spontaneous retinal venous pulsation is seen as a subtle variation in the calibre of the retinal vein(s) as they cross the optic disc. The physical principles behind the venous pulsations has been the point of much debate. Initial theories suggested that the pulsation occurred because of the rise in intraocular pressure in the eye with the pulse pressure. This article presents an argument that this is not the case. The pulsations are in fact caused by variation in the pressure gradient along the retinal vein as it traverses the lamina cribrosa. The pressure gradient varies because of the difference in the pulse pressure between the intraocular space and the cerebrospinal fluid. The importance of this is that as the intracranial pressure rises the intracranial pulse pressure rises to equal the intraocular pulse pressure and the spontaneous venous pulsations cease. Thus it is shown that cessation of the spontaneous venous pulsation is a sensitive marker of raised intracranial pressure. The article discusses the specificity of the absence of spontaneous venous pulsation and describes how the patient should be examined to best elicit this important sign.

[Circulatory consequences of retinal vein occlusions. Advantages of dynamic angiography]

PURPOSE

To compare angiographic features in patients with branch vein (BRVO) and central retinal vein occlusion (CRVO) and to discuss their possible significance.

PATIENTS AND METHODS

Clinical and indocyanine green (ICG) videoangiographic data of 35 patients with CRVO and 5 patients with BRVO were reviewed. In order to more fully understand the significance of hemodynamic alterations, patients with a decrease in retinal flow velocity from other causes (optic neuritis, carotid-cavernous fistula, carotid artery stenosis) were compared to patients with vein occlusion.

RESULTS

Whatever the type of occlusion, the most frequent abnormality was the presence of pulsatile venular outflow, which at the acute phase was present in the majority of cases. The decrease in arterial velocity was visualized by the presence of diastolic reversed flow. There was no correlation between visual prognosis and hemodynamic alterations. Apart from vein occlusion, the pulsatile venular outflow was present in situations where increased venous pressure was present.

CONCLUSIONS

BRVO and CRVO have similar alterations of venous flow. Videoangiography can electively show pulsatile venular outflow and reverse diastolic arterial flow, and thus contributes additional information to conventional angiography. Pulsatile venular outflow is probably due to a combination of elevated venous pressure and decreased plasma velocity. Videoangiography provides new insight to the consequences of retinal vein occlusion and will possibly lead to a better understanding of the sequence of events that lead to visual loss.

Retinal vascular changes and systemic diseases: corrosion cast demonstration

The purpose of the present study is to clarify the specific retinal vascular changes in rat models of single spontaneous or hereditary systemic diseases. We used Wistar Kyoto (WKy) rats 6 months of age as normal controls, 24-month-old Wistar Kyoto rats in studies of aging, 16-month-old spontaneously hypertensive rats (SHR), 18-month-old rats with inherited hypercholesterolemia (RICO) for arteriosclerosis, and 18-month-old Otsuka Long-Evans Tokushima Fatty (OLETF) rats for diabetes mellitus. Retinal vascular corrosion casts were made and observed with a scanning electron microscope. The retinal vessels were also examined with a transmission electron microscope. Specific changes in the retinal vessels were: narrowing and thin thread-like capillaries in aging; capillary tortuosity, irregularity and narrowing in hypertension; straightening in hypercholesterolemia; and loop formation and microaneurysms in diabetes mellitus. These specific changes in the retinal vessels in each systemic disease can be clearly and easily revealed in a three-dimensional fashion by corrosion casts followed by scanning electron microscopy.

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.

Extraction and modeling of the Oscillatory Potential: signal conditioning to obtain minimally corrupted Oscillatory Potentials

A method of extracting a temporally bounded component of a composite signal has been developed which minimizes data corruption in signal processing. The composite signal is windowed in the time domain, padding signals are attached, and finally, the conditioned signal is filtered to extract the component of interest. The method has been utilized to extract the Oscillatory Potential (OP) from the Electroretinogram (ERG). ERGs can contain impulse like transients, including flash artifacts and a-b wave transition, which may not be related to the Oscillatory Potential. Such transients will stimulate a filter, yielding its natural (filter) response and thus distort the actual OP signal. To avoid this effect, time-domain windowing and signal conditioning is used to extract the OP from the ERG. The extraction and modeling approach is applied to ERGs obtained from patients with recent monocular central retinal vein occlusion (CRVO). Model parameters clearly differentiate affected from fellow eyes and show subtle differences between eyes with benign and complicated outcomes.

Treatment of retinal vein thrombosis with pentoxifylline: a controlled, randomized trial

The aim of this study was to evaluate PXF (pentoxifylline; 1600 mg daily vs placebo) in patients with retinal vein thrombosis (RVT) in a 4-week trial, evaluating clinical outcome and retinal flow. Inclusion criteria were sudden loss of vision (SLV); retinal vein thrombosis (RVT); decrease in retinal vein flow; asymmetry between retinal veins (>40%) documented by duplex scanning (retinal vein thrombosis flow = RVTF). All 18 included patients completed the study. The groups were comparable. No side effect was observed. An improvement in arterial flow (p<0.05) and a decrease in analogue score (p<0.05) were observed in both groups (due to the spontaneous evolution with partial thrombus lysis in 4 weeks). The increase in arterial flow (PSF and EDF) were greater (p<0.05) in the PXF group. The RVFV increase was better in the PXF group (350% increase vs 200% increase in the placebo group; p<0.05). There was a significant difference in the analogue score decrease (4 vs 7) in the PXF group (p<0.05). In conclusion, PXF improved retinal flow after RVT better than placebo. It should be considered as an important treatment option.

[Isolated and combined occlusion of the cilioretinal artery and the central retinal vein]

Cilioretinal artery occlusion is rare pathological condition because of infrequent occurrence of the cilioretinal artery in the human retina. It presents as an isolated entity, or as a combined cilioretinal artery--central retinal vascular, mostly venous occlusion. Authors present the course, angiographic features, prognosis, risk factors and final outcome of the isolated cilioretinal artery occlusion and combined cilioretinal artery--central retinal vein occlusion. Occlusion of the cilioretinal artery is believed to result from obstruction of the central retinal vein, as a primary process, in the case of combined cilioretinal artery--central retinal vein occlusion.

Investigation of blood flow velocity by color Doppler imaging in nonischemic central retinal vein occlusion with collateral veins

PURPOSE

To study the blood flow velocity in the central retinal vein after the resolution of non-ischemic central retinal vein occlusion (CRVO) with optociliary vein (OCV).

METHODS

Eleven patients and 22 healthy volunteers were studied. Indocyanine green (ICG) angiography was used to investigate the choroidal veins in the affected eyes. Color Doppler imaging was used to measure the blood velocity in the central retinal artery and vein in the 11 affected and 22 healthy eyes.

RESULTS

Indocyanine green angiography verified the formation of retinochoroidal collaterals in all the affected eyes. The velocity in the central retinal vein was significantly lower in the affected eyes.

CONCLUSIONS

The results indicate that the collaterals are important routes of extraretinal outflow of retinal venous blood. It is recommended in the investigation of CRVO by color Doppler imaging to perform ICG angiography to determine if retinochoroidal collateral veins have been formed.