The retinal venous pressure at different levels of airway pressure measured with a new method.

PURPOSE: This study is to investigate the increase in retinal venous pressure (RVP) induced by a stepwise increase in airway pressure (AirP) using the new IOPstim method, which is designed to artificially increase the intraocular pressure (IOP) and thus to stimulate vascular pulsation. METHODS: Twenty-eight healthy subjects were examined in the left eye. The RVP was measured at baseline and at four different levels of AirP (10, 20, 30, and 40 mmHg) using the new IOPstim method: a half balloon of 8 mm diameter is inflated laterally to the cornea under observation of the central retinal vein. As soon as the vein pulsates at a certain AirP level, the IOP is measured with a commercially available tonometer, which then corresponds to the RVP. RESULTS: Spontaneous venous pulsation was observed in all study participants. The mean RVP values at baseline and at the AirP levels of 10, 20, 30, and 40 mmHg were 17.6 ± 2.8 mmHg; 20.1 ± 3.0 mmHg; 22.1 ± 3.5 mmHg; 24.3 ± 3.7 mmHg, and 26.6 ± 4.2 mmHg, respectively. The mean RVP values of each AirP level were statistically significantly different from each other in pairwise comparison. In a linear mixed model, the effect of AirP on RVP was highly significant (p < 0.001). In the model, a 10-mmHg increase in AirP resulted in a linear increase in RVP of 2.2 mmHg. CONCLUSION: An increase in AirP was accompanied by a linear increase in RVP. The influence of AirP on RVP, and thus on retinal perfusion pressure during the Valsalva maneuver, is less than was assumed based on previous studies in which contact lens dynamometry was used.

Retinal vessel caliber and caliber responses in true normotensive black and white adults: The African-PREDICT study.

PURPOSE: Globally, a detrimental shift in cardiovascular disease risk factors and a higher mortality level are reported in some black populations. The retinal microvasculature provides early insight into the pathogenesis of systemic vascular diseases, but it is unclear whether retinal vessel calibers and acute retinal vessel functional responses differ between young healthy black and white adults. METHODS: We included 112 black and 143 white healthy normotensive adults (20-30 years). Retinal vessel calibers (central retinal artery and vein equivalent (CRAE and CRVE)) were calculated from retinal images and vessel caliber responses to flicker light induced provocation (FLIP) were determined. Additionally, ambulatory blood pressure (BP), anthropometry and blood samples were collected. RESULTS: The groups displayed similar 24 h BP profiles and anthropometry (all p > .24). Black participants demonstrated a smaller CRAE (158 ±â€¯11 vs. 164 ±â€¯11 MU, p < .001) compared to the white group, whereas CRVE was similar (p = .57). In response to FLIP, artery maximal dilation was greater in the black vs. white group (5.6 ±â€¯2.1 vs. 3.3 ±â€¯1.8%; p < .001). CONCLUSIONS: Already at a young age, healthy black adults showed narrower retinal arteries relative to the white population. Follow-up studies are underway to show if this will be related to increased risk for hypertension development. The reason for the larger vessel dilation responses to FLIP in the black population is unclear and warrants further investigation.

Detection and characterization of tree shrew retinal venous pulsations: An animal model to study human retinal venous pulsations.

Spontaneous retinal venous pulsations (SRVPs), pulsations of branches of the central retinal vein, are affected by intraocular pressure (IOP) and intracranial pressure (ICP) and thus convey potentially-useful information about ICP. However, the exact relationship between SRVPs, IOP, and ICP is unknown. It is not easily feasible to study this relationship in humans, necessitating the use of an animal model. We here propose tree shrews as a suitable animal model to study the complex relationship between SRVPs, IOP, and ICP. Tree shrew SRVP incidence was determined in a population of animals. Following validation of a modified IOP control system to accurately and quickly control IOP, IOP and/or ICP were manipulated in two tree shrews with SRVPs and the effects on SRVP properties were quantified. SRVPs were present in 75% of tree shrews at physiologic IOP and ICP. Altering IOP or ICP produced changes in tree shrew SRVP properties; specifically, increasing IOP caused SRVP amplitude to increase, while increasing ICP caused SRVP amplitude to decrease. In addition, a higher IOP was necessary to generate SRVPs at a higher ICP than at a lower ICP. SRVPs occur with a similar incidence in tree shrews as in humans, and tree shrew SRVPs are affected by changes in IOP and ICP in a manner qualitatively similar to that reported in humans. In view of anatomic similarities, tree shrews are a promising animal model system to further study the complex relationship between SRVPs, IOP, and ICP.

COMPARISON OF THE RETINAL BLOOD FLOW VELOCITY BETWEEN LASER SPECKLE FLOWGRAPHY AND THE RETINAL FUNCTION IMAGER.

PURPOSE: To compare the retinal blood flow velocity using laser speckle flowgraphy (LSFG) and a retinal function imager (RFI) in healthy Japanese subjects. METHODS: This study included a total of 15 eyes of 15 healthy Japanese subjects (mean age, 41.7 ± 17.0 years). The retinal blood flow velocities were separately measured in arteries and veins around the optic disc using LSFG and an RFI. Linear regression analyses were used to analyze possible correlations of retinal blood flow velocities between the devices. RESULTS: The average blood flow velocities using LSFG as the mean blur rate were 18.6 ± 4.8 in arteries and 18.3 ± 5.5 in veins. The average blood flow velocities using the RFI were 3.4 ± 1.1 mm/second in arteries and 2.9 ± 0.9 mm/second in veins. Although retinal blood flow velocities in arteries and veins using LSFG were nearly the same, there were statistical differences in retinal blood flow velocities between arteries and veins using the RFI (P = 0.701 using LSFG, P = 0.041 using the RFI). Significant correlations were found between LSFG and the RFI in arteries and veins (all, P < 0.001). CONCLUSION: There were strong positive correlations in retinal blood flow velocities between LSFG and the RFI in healthy subjects.

Doppler ultrasonographic measurement of short-term effects of valsalva maneuver on retrobulbar blood flow.

BACKGROUND: To investigate the effects of Valsalva maneuver (VM) on retrobulbar blood flow parameters in healthy subjects. METHODS: Participants without any ophthalmologic or systemic pathology were examined in supine position with color and pulsed Doppler imaging for blood flow measurement, via a paraocular approach, in the ophthalmic artery (OA), central retinal artery (CRA), central retinal vein (CRV), nasal posterior ciliary artery (NPCA), and temporal posterior ciliary artery (TPCA), 10 seconds after a 35- to 40-mm Hg expiratory pressure was reached. Peak systolic velocity (PSV), end-diastolic velocity (EDV), pulsatility index (PI), and resistivity index (RI) values were recorded for each artery. PSV and EDV values were recorded for CRV. RESULTS: There were significant differences between resting and VM values of PSV and EDV of CRA, RI of NPCA, and PI, RI, and EDV of TPCA. Resting CRA-EDV, CRV-PSV, and CRV-EDV were positively correlated whereas resting OA-PSV and CRA-PI, and OA-PSV, CRA-PSV, and CRA-EDV during VM, were negatively correlated with age. CONCLUSIONS: VM induces a short-term increase in CRA blood flow and a decrease in NPCA and TPCA RI. Additional studies with a longer Doppler recording during VM, in a larger population sample, are required to allow definitive interpretation. © 2017 Wiley Periodicals, Inc. J Clin Ultrasound 45:551-555, 2017.

Changes in Retinal Nonperfusion Associated with Suppression of Vascular Endothelial Growth Factor in Retinal Vein Occlusion.

PURPOSE: To assess changes in retinal nonperfusion (RNP) in patients with retinal vein occlusion (RVO) treated with ranibizumab. DESIGN: Secondary outcome measure in randomized double-masked controlled clinical trial. PARTICIPANTS: Thirty-nine patients with central RVO (CRVO) and 42 with branch RVO (BRVO). METHODS: Subjects were randomized to 0.5 or 2.0 mg ranibizumab every month for 6 months and then were re-randomized to pro re nata (PRN) groups receiving either ranibizumab plus scatter laser photocoagulation or ranibizumab alone for an additional 30 months. MAIN OUTCOME MEASURES: Comparison of percentage of patients with increased or decreased area of RNP in patients with RVO treated with 0.5 versus 2.0 mg ranibizumab, during monthly injections versus ranibizumab PRN, and in patients treated with ranibizumab PRN versus ranibizumab PRN plus laser. RESULTS: In RVO patients given monthly injections of 0.5 or 2.0 mg ranibizumab for 6 months, there was no significant difference in the percentage who showed reduction or increase in the area of RNP. However, regardless of dose, during the 6-month period of monthly injections, a higher percentage of patients showed a reduction in area of RNP and a lower percentage showed an increase in area of RNP compared with subsequent periods of ranibizumab PRN treatment. After the 6-month period of monthly injections, BRVO patients, but not CRVO patients, randomized to ranibizumab PRN plus laser showed significantly less progression of RNP compared with patients treated with ranibizumab PRN. CONCLUSIONS: Regardless of dose (0.5 or 2.0 mg), monthly ranibizumab injections promote improvement and reduce progression of RNP compared with PRN injections. The addition of scatter photocoagulation to ranibizumab PRN may reduce progression of RNP in patients with BRVO, but a statistically significant reduction was not seen in patients with CRVO.

Phase and amplitude of spontaneous retinal vein pulsations: An extended constant inflow and variable outflow model.

The constant inflow and variable outflow (CIVO) theory correctly predicts that spontaneous pulsation of the retinal veins will be visible close to the point where the vein exits the eye at the lamina cribrosa but will decrease rapidly in amplitude and become too small to see only a short distance upstream. However, the phase of vein oscillation relative to the oscillation of the intraocular pressure (IOP) predicted by CIVO has been unclear and controversial. We show that the CIVO model is indeterminate in predicting such phase relations. We propose a simple extension of the CIVO model that retains its basic equations but applies them to a larger domain that includes not only the intraocular (pre-laminar) portion of the vein but also the retrobulbar (post-laminar) portion of the vein behind the eye. We show that this extended CIVO model makes definite predictions about the phase of vein oscillation relative to the oscillation of IOP. This phase relationship is determined by the relative amplitude and phase of pulsations of the IOP and of the cerebrospinal fluid pressure (CSFP). If IOP and CSFP oscillate in phase, then the pre-laminar vein oscillates in phase with IOP when the amplitude of CSFP exceeds the amplitude of IOP but oscillates in counter phase with IOP when the amplitude of IOP exceeds that of CSFP. These relationships are modified when there is a phase difference between the oscillations of IOP and CSFP. When CSFP leads IOP, the phase of vein oscillation is advanced if the amplitude of CSFP exceeds that of IOP and is delayed if the amplitude of IOP exceeds that of CSFP. The result in each case is that maximum vein size occurs during the rising phase of IOP (ocular systole). We conclude that the driving force of vein oscillation is the difference between the oscillations of IOP and CSFP. The phase of this difference determines the phase relationships above. We show that additional delays in the phase of venous pulsation relative to that of IOP are induced by constriction of the vein within the lamina cribrosa and by recording the vein pulsations upstream from the lamina cribrosa. The amplitude of vein oscillation is proportional to the amplitude of the driving force and to the venous capacitance. Loss of spontaneous retinal vein pulsation with increase in mean CSFP is determined primarily by reduced venous capacitance. Increased amplitude of pulsation may occur when IOP is increased. It is the result of increased venous capacitance and possibly increased driving force of the pulsation. However, in chronic glaucoma the increase in capacitance may be counteracted by venous outflow obstruction, and the increase in driving force may be counteracted by reduced ocular blood flow. As a result retinal vein oscillation may be reduced in amplitude.

Structural characteristics of the optic nerve head influencing human retinal venous pulsations.

The relationship between structural characteristics of the optic nerve head and venous pulsations in the human eye remain unknown. Using photoplethysmographic techniques we investigated whether properties of the human retinal veins and their surrounding structures influence venous pulsation. 448 locations of venous pulsation were analysed from 26 normal human eyes. Green channel densitometry derived from video recordings of venous pulsations were used to generate a map of venous pulsation amplitudes along retinal veins. Optical coherence tomography was used to perform quantitative measurements of tissue characteristics at sites of high and low amplitude points as well as in a second analysis, at maximal amplitude pulsation sites from superior and inferior halves of the eyes. Structural characteristics measured included venous diameter, distance from pulsation point to cup margin, vessel length from pulsation point to vein exit, tissue thickness overlying vein, optic disc diameter and presence of a proximal arteriovenous crossing. Increasing venous pulsation amplitudes were associated with larger applied ophthalmodynamometry force, increasing venous diameter, and decreasing absolute cup margin distance (all p < 0.001). Increasing distance of maximal amplitude pulsation point to cup margin was associated with the presence of a proximal arteriovenous crossing, increasing venous diameter, and decreasing tissue depth (all p ≤ 0.001). Venous diameter and tissue depth alter venous compliance, which is likely to be a major factor determining sites of venous pulsation.

Assessment of potential vessel segmentation pitfalls in the analysis of blood flow velocity using the Retinal Function Imager.

PURPOSE: The purpose of our study was to investigate the potential pitfalls associated with different vessel segmentation methods using the built-in software of the Retinal Function Imager (RFI) for the analysis of retinal blood flow velocity (BFV). METHODS: Ten eyes of nine healthy subjects were enrolled in the study. Retinal blood flow measurements were obtained with the RFI device with a 20° field of view imaging. The same grader segmented the retinal vasculature using the RFI software in both sessions, with segments ranging in length from 50 to 100 pixels ("short segments") and 100-200 pixels ("long segments"). The blood flow velocities for the arteriolar and venular system were calculated, and the percentage of excluded vessel segments with high coefficients of variation (>45 %) was recorded and compared by paired t test. Spearman's correlation was used to analyze the relationship between measurements by the two vessel segmentation methods. RESULTS: The number of analyzed vessel segments did not differ significantly between the two groups (28.6 ± 2.6 short and 26.7 ± 4.6 long segments), while the percentage of acceptable segments was significantly higher in the long segment group (65.2 ± 11.4 % vs 85.2 ± 5.87 %, p = 0.001). In the short segment group, more than 15 % of vessel segments were rejected in all subjects, while in the long segment group only three subjects had a rejection rate of greater than 15 % (16.7 %, 18.7 % and 28 %). Both arteriolar and venular velocities were lower in the short segment group, although it reached significance only for arteriolar velocities (3.93 ± 0.55 vs. 4.45 ± 0.76 mm/s, p = 0.036 and 2.95 ± 0.56 vs. 3.17 ± 0.84 mm/s, p = 0.201 for arterioles and venules, respectively). Only venular velocities showed significant correlation (p = 0.003, R (2) = 0.67) between the two groups. CONCLUSIONS: Our results suggest that BFV measurements by the RFI may be affected by segment length, and care should therefore be taken in choosing vessel segment lengths used during the analysis of RFI data. Long segments of 100-200 pixels (400-800 µm) seem to provide more robust measurements, which can be explained by the analysis methodology of the RFI device.

Imaging pulse wave propagation in human retinal vessels using full-field swept-source optical coherence tomography.

We demonstrate a new noninvasive method to assess biomechanical properties of the retinal vascular system. Phase-sensitive full-field swept-source optical coherence tomography (PhS-FF-SS-OCT) is used to investigate retinal vascular dynamics at unprecedented temporal resolution. The motion of retinal tissue that is induced by expansion of the vessels therein is measured with an accuracy of about 10 nm. The pulse shapes of arterial and venous pulsations, their temporal delays, as well as the frequency-dependent pulse propagation through the capillary bed, are determined. For the first time, imaging speed and motion sensitivity are sufficient for a direct measurement of pulse waves propagating with more than 600 mm/s in retinal vessels of a healthy young subject.

Venous oxygen saturation is reduced and variable in central retinal vein occlusion.

PURPOSE: To estimate the presence and variability of retinal hypoxia in patients with central retinal vein occlusion (CRVO). METHOD: Hemoglobin oxygen saturation was measured in retinal vessels of both eyes in 14 patients with unilateral CRVO. The noninvasive spectrophotometric retinal oximeter is based on a fundus camera and simultaneously captures two images at 570 nm and 600 nm wavelengths. Five of the patients were followed with repeated retinal oximetry images over time. RESULTS: The mean oxygen saturation in retinal venules was 31 % ±12 % in CRVO eyes and 52 % ±11 % in unaffected fellow eyes (mean ±SD, n = 14, p < 0.0001). The arteriovenous difference was 63 % ±11 % in eyes with CRVO and 43 % ±7 % in fellow eyes (p < 0.0001). The variability of retinal venous oxygen saturation was substantial within and between eyes affected by CRVO. Venular oxygen saturation improved with treatment and over time in all five patients that were followed. CONCLUSION: CRVO eyes are hypoxic compared to fellow eyes and arteriovenous difference in hemoglobin oxygen saturation is increased. This is consistent with tissue hypoxia resulting from reduced blood flow. Further studies are needed to understand the correlation between hypoxia, severity of disease and prognosis.

[Physiological basis of the microcirculation: vascular adaptation]. / Physiologische Grundlagen der Mikrozirkulation: vaskuläre Adaptation.

The microcirculation is the functional "business end" of the cardiovascular system. In vessels with diameters below about 300 µm processes including the regulation of perfusion, exchange processes and relevant components of the immune system are localised. A large number of individual mechanisms are involved, including micro-rheology, the endothelial surface layer, vascular permeability, endothelial function, regulation of smooth muscle tone, leukocyte endothelial interaction, vascular adaptation and angiogenesis. The present article focusses mainly on the role of vascular adaptation. Much more than in large vessels, the microcirculation is characterised by constant adaptation to haemodynamic and metabolic signals. In reaction to changes in parenchymal demand, changes of the diameter of existing vessels (by changes in tone or by structural remodelling) as well as generation of new vessels (angiogenesis) or the pruning of vessels are elicited. These mechanisms are part of the so-called "angioadaptation" which is of great clinical relevance for the pathophysiological consequences of hypertension and age-related macular degeneration.

Acridine orange leukocyte fluorography in mice.

Simultaneous non-invasive visualization of blood vessels and nerves in patients can be obtained in the eye. The retinal vasculature is a target of many retinopathies. Inflammation, readily manifest by leukocyte adhesion to the endothelial lining, is a key pathophysiological mechanism of many retinopathies, making it a valuable and ubiquitous target for disease research. Leukocyte fluorography has been extensively used in the past twenty years; however, fluorescent markers, visualization techniques, and recording methods have differed between studies. The lack of detailed protocol papers regarding leukocyte fluorography, coupled with lack of uniformity between studies, has led to a paucity of standards for leukocyte transit (velocity, adherence, extravasation) in the retina. Here, we give a detailed description of a convenient method using acridine orange (AO) and a commercially available scanning laser ophthalmoscope (SLO, HRA-OCT Spectralis) to view leukocyte behavior in the mouse retina. Normal mice are compared to mice with acute and chronic inflammation. This method can be readily adopted in many research labs.

Retinal venous pressure in the non-affected eye of patients with retinal vein occlusions.

BACKGROUND: To measure the retinal venous pressure (RVP) in both eyes of patients with unilateral central retinal vein occlusions and to compare these values to controls. METHODS: The study included 31 patients with unilateral central retinal vein occlusions (CRVO) and 31 controls who were matched by age, sex, and systemic disease. RVP was measured in all patients bilaterally by means of contact lens ophthalmodynamometry, and the RVP measurements of the affected and unaffected eyes of patients were compared to the RVPs of controls. Ophthalmodynamometry is done by applying an increasing pressure on the eye via a contact lens. The minimum force required to induce a venous pulsation is called ophthalmodynamometric force (ODF). The RVP is defined and calculated as the sum of ODF and intraocular pressure (IOP) [RVP = ODF + IOP]. RESULTS: The RVP group means ± SD were as follows: patient's affected eyes (45.0 ± 11.6 mmHg), patient's unaffected eyes (38.0 ± 11.1 mmHg) ,and (17.7 ± 6.7 mmHg) in the eyes of controls. The values of RVP, even in the patients unaffected eyes, were significantly higher than in the eyes of controls (P < 0.001). CONCLUSIONS: In patients with CRVO, the RVP is increased in both the affected as well as in the unaffected contralateral eye.

Normative values and predictors of retinal oxygen saturation.

PURPOSE: To determine normal retinal oxygen saturation (SO2) values measured with retinal oximetry in a multiethnic group of healthy subjects and to evaluate the association of retinal SO2 with demographic and clinical parameters. METHODS: Retinal oximetry was performed in both eyes of 61 normal healthy subjects. Global and quadrant venous (SvO2) and arterial oxygen saturation (SaO2), arteriovenous difference in SO2, and venular and arteriolar width were measured. The association of SO2 parameters with age, gender, ethnicity, refraction, iris color, history of controlled systemic hypertension, and smoking was analyzed. RESULTS: Average SvO2 and SaO2 were 55.3 ± 7.1% and 90.4 ± 4.3%, respectively. All average measurements were comparable in both eyes, both genders, and among ethnic groups. Inferonasal quadrant SaO2 was higher in Asians. Age was associated with decreased SvO2 (ß = -0.19; P = 0.001) and SaO2 (ß = -0.11; P = 0.003). History of controlled systemic hypertension was associated with an increase in arteriovenous difference in SO2 (ß = 3.99; P = 0.013). CONCLUSION: This is the first description of retinal SO2 in healthy, multiethnic subjects. Aging decreases SvO2 and SaO2 and should be accounted for when interpreting retinal oximetry measurements. Other demographic and clinical parameters studied did not seem to significantly influence retinal SO2 measurements.

The effect of flammer-syndrome on retinal venous pressure.

BACKGROUND: The purpose of the study was to measure the retinal venous pressure (RVP) in the eyes of primary open-angle glaucoma (POAG) patients and healthy subjects with and without a Flammer-Syndrome (FS). METHODS: RVP was measured in the following four groups of patients and age- and sex-matched healthy controls: (a) 15 patients with a POAG and a FS (POAG/FS+); (b) 15 patients with a POAG but without a FS (POAG/FS-); (c) 14 healthy subjects with a FS (healthy/FS+) and (d) 16 healthy subjects without a FS (healthy/FS-). RVP was measured in all participants bilaterally by means of contact lens ophthalmodynamometry. Ophthalmodynamometry is done by applying increasing pressure on the eye via a contact lens. The minimum force required to induce a venous pulsation is called ophthalmodynamometric force (ODF). The RVP is defined and calculated as the sum of ODF and intraocular pressure (IOP) [RVP = ODF + IOP]. RESULTS: The participants with a FS (whether patients with POAG or healthy subjects), had a significantly higher RVP compared to subjects without a FS (p = 0.0103). Patients with a POAG and FS (POAG/FS+) had a significantly higher RVP compared to patients without a FS (POAG/FS-) (p = 0.0301). There was a notable trend for a higher RVP in the healthy/FS + group compared to the healthy/FS - group, which did not reach statistical significance (p = 0.0898). CONCLUSIONS: RVP is higher in subjects with a FS, particularly in glaucoma patients. The causal relationship needs to be further evaluated.

Test-retest reliability of retinal oxygen saturation measurement.

PURPOSE: To determine intrasession and intersession repeatability of retinal vessel oxygen saturation from the Oxymap Retinal Oximeter using a whole image-based analysis technique and so determine optimal analysis parameters to reduce variability. METHODS: Ten fundus oximetry images were acquired through dilated pupils from 18 healthy participants (aged 22 to 38) using the Oxymap Retinal Oximeter T1. A further 10 images were obtained 1 to 2 weeks later from each individual. Analysis was undertaken for subsets of images to determine the number of images needed to return a stable coefficient of variation (CoV). Intrasession and intersession variability were quantified by evaluating the CoV and establishing the 95% limits of agreement using Bland and Altman analysis. Retinal oxygenation was derived from the distribution of oxygenation values from all vessels of a given width in an image or set of images, as described by Paul et al. in 2013. RESULTS: Grouped in 10-µm-wide bins, oxygen saturation varied significantly for both arteries and veins (p < 0.01). Between 110 and 150 µm, arteries had the least variability between individuals, with average CoVs less than 5% whose confidence intervals did not overlap with the greater than 10% average CoVs for veins across the same range. Bland and Altman analysis showed that there was no bias within or between recording sessions and that the 95% limits of agreement were generally lower in arteries. CONCLUSIONS: Retinal vessel oxygen saturation measurements show variability within and between clinical sessions when the whole image is used, which we believe more accurately reflects the true variability in Oxymap images than previous studies on select image segments. Averaging data from vessels 100 to 150 µm in width may help to minimize such variability.

The effect of acetazolamide on different ocular vascular beds.

PURPOSE: To assess the effect of acetazolamide (AZ) on different ocular vascular beds. METHODS: In a prospective study, 32 healthy volunteers (16 male, 16 female) with a mean age of 23.9 ± 3.3 years (20-39 years) were included. Before and after intravenous administration of 1,000 mg AZ (single dose), ocular microcirculation parameters were measured every 20 min for 2 h. Retinal vessel diameters (VD) were measured by the retina vessel analyzer, blood flow (BF) in the neuroretinal rim by the laser doppler flowmeter according to Riva, and the parapapillary retinal BF by the scanning laser Doppler flowmeter. Additionally, the Langham ocular blood flow system was used to determine the ocular pulse amplitude (OPA) and the pulsatile ocular blood flow (pOBF). The measurements were correlated with systemic blood pressure (BP), ocular perfusion pressure (OPP), capillary base excess parameters and serum AZ levels. RESULTS: Arterial and venous VD were significantly increased by about 4-5% each. Papillary BF increased significantly about 40%. Parapapillary retinal flow dropped significantly about 19% (120 min). OPA and pOBF showed no statistically significant changes. BP showed no significant changes, and OPP was significantly increased. There were no correlations with pH or systemic perfusion parameters. CONCLUSIONS: AZ leads to a dilatation of retinal VD, to an increase of BF in the optic nerve head, and to a decrease of parapapillary retinal BF. The different BF changes in different vascular beds might be due to different regulatory mechanisms, steal effects, or different distributions of the carbonic anhydrase.

Score Study Report 12: Development of venous collaterals in the Score Study.

PURPOSE: To investigate the prevalence of venous collaterals after branch and central retinal vein occlusion, assess the association of venous collaterals with other clinical features (including visual acuity), and determine if treatment with intravitreal corticosteroids influences the development of new venous collaterals. METHODS: Review of data from two multicenter randomized clinical trials in the Standard of Care versus COrticosteroid for REtinal Vein Occlusion (SCORE) Study. RESULTS: Statistically significant associations of venous collaterals and visual acuity at baseline or at follow-up were not found. Treatment with intravitreal triamcinolone acetonide did not appear to influence the development of venous collaterals. CONCLUSION: In contrast to some previous reports, development of venous collaterals did not demonstrate an independent association with visual acuity in eyes with branch retinal vein occlusion or central retinal vein occlusion in the SCORE Study. Intravitreal steroid effects do not appear to influence the development of venous collaterals.

The clinical validity of the spontaneous retinal venous pulsation.

BACKGROUND: The validity of the clinical dictum "the presence of spontaneous retinal venous pulsation (SVP) excludes raised intracranial pressure" has not been previously tested. We set out to determine the specificity and positive predictive value (PPV) of the presence of SVP to indicate normal intracranial pressure (ICP) in a routine clinical setting. METHODS: We prospectively recruited patients undergoing lumbar puncture (LP), and 2 clinicians were blinded to the indications for LP and cerebrospinal fluid opening pressure (OP). Interobserver reliability was assessed. RESULTS: There were 106 patients in our cohort with a median age of 44 years (range, 18-79 years) and median body mass index of 27.5 kg/m (range, 18-48 kg/m). SVP was present in 94 of 106 patients (88.7%). Thirteen of 106 (12.3%) patients had high OP (≥30 cmH2O), and SVP was present in 11 of 13 patients (86%) with high OP. The sensitivity (95% confidence interval) of the presence of SVP to exclude raised ICP was 0.89 (0.88-0.92), specificity of 0.15 (0.05-0.37), PPV of 0.88 (0.87-0.9), and negative predictive value of 0.17 (0.05-0.4). Interobserver agreement was moderate for SVP (kappa = 0.42). CONCLUSIONS: Although the sensitivity and PPV of the presence of SVP to exclude raised ICP is high, it is not absolute. SVP can be seen in some patients with high ICP. Relying on the presence of SVP to exclude raised ICP may give a false sense of reassurance.