Ocular Blood Flow Parameters Research Articles

Ocular Blood Flow Changes in Behçet Disease Patients with/without Thrombotic Disease

ABSTRACTIn this study, the authors aimed to evaluate ocular blood flow changes in Behçet disease (BD) with and without thrombotic disease. Ninety eyes of 90 patients with a diagnosis of BD (30 eyes with active uveitis, 23 eyes with inactive uveitis, 25 eyes without ocular involvement, and 12 eyes without ocular involvement and with a history of thrombosis) and 30 eyes of 30 age- and sex-matched control patients without any systemic disease with a total of 120 eyes were evaluated. In all cases, ophthalmic, central retinal, and ciliary artery flow parameters were measured with colour Doppler ultrasonography (CDU). The ocular blood flow parameters of all vessels in patients with active uveitis were found to be affected. All the flow parameters in the CRAs of the study groups were significantly different from the control group (p < 0.001). Additionally, in non-ocular BD patients with thrombosis, blood flow parameters were affected more than the parameters in non-ocular BD patients without thrombosis and control patients. In conclusion, major haemodynamic changes were observed using CDU in the ophthalmic vessels of ocular Behçet patients. Also, CDU may detect ocular blood flow alterations before initial ocular clinical manifestations appear in BD patients

Ocular haemodynamics in patients with type 2 diabetes and coronary artery disease

Background/aimsTo assess the relationship between ocular blood flow parameters and diabetic retinopathy and coronary artery disease in diabetic patients.Methods56 patients participated in the study. Colour Doppler imaging was used to...

Interaction between leukocytes and erythrocytes in the human retina: Effects of pentoxifylline on hyperoxia-induced vasoconstriction during increased neutrophil counts

PurposePentoxifylline, a nonselective phosphodiesterase inhibitor, shows vasodilator effects in certain vascular beds and reduces blood viscosity. We have previously shown that under states of vasoconstriction an interaction between circulating erythrocytes and leukocytes may play a role in the control of blood flow. The reason for this observation is not entirely clear but may be related to a mechanical interaction between red and white blood cells. In the present study we hypothesized that pentoxifylline may alter this interaction during oxygen-induced vasoconstriction. Methods24 healthy male subjects participated in this double masked, randomized, placebo-controlled 2 way cross over trail. In order to increase white blood cell count (WBC) count, 300μg of G-CSF was administered intravenously. Vasoconstriction of retinal vessels was induced by oxygen inhalation. 400mg of pentoxifylline or placebo was infused at two different study days. White blood cell flux was assessed with the blue-field entoptic technique. Vessel calibers were measured with a dynamic vessel analyzer (DVA) and red blood cell velocity (RBCV) was determined with laser Doppler velocimetry (LDV). Retinal blood flow was calculated based on retinal vessel diameters and RBCV. ResultsAdministration of G-CSF induced a significant increase in WBC, both in the placebo and the pentoxifylline group (p<0.01 for both groups). Retinal vessel diameter, RBCV, calculated retinal blood flow and white blood cell flow were not altered by administration of pentoxifylline. Hyperoxia induced a pronounced decrease in retinal blood flow parameters. No difference was observed between groups during oxygen breathing in vessel diameters (p=0.54), RBCV (p=0.34), calculated retinal blood flow (p=0.3) and white blood cell flow (p=0.26). ConclusionOur data indicate that short time administration of pentoxifylline does not alter the oxygen-induced effect on ocular blood flow parameters during leukocytosis. Whether long-term treatment could improve retinal blood flow under states of vasoconstriction remains to be investigated.

Assessment of ocular hemodynamics after laser in situ keratomileusis using color Doppler imaging

To investigate ocular blood flow changes in healthy myopic patients following laser in situ keratomileusis (LASIK) using color Doppler imaging. Sixteen eyes of 16 myopic patients were studied. LASIK was performed and intraocular pressure was raised to levels ≥65 mmHg. Color Doppler images were obtained to study the ophthalmic and central retinal arteries preoperatively and postoperatively at 1 day, 1 week, and 1 month. There was no significant correlation between patient age and preoperative ocular blood flow parameters. A significant positive correlation between the degree of myopia and the peak systolic volume of the ophthalmic artery (r = 0.6, P = 0.01) was found. A highly significant decrease in the peak systolic volume and end-diastolic volume with an increase in the resistive index of both arteries (P < 0.005) was seen at 1 day and 1 week postoperatively. There was no significant difference between the preoperative and postoperative data 1 month after the procedure. The findings of this study show temporary alterations in ocular blood flow parameters after LASIK. LASIK is an increasingly common lifestyle procedure and further studies on larger groups are still recommended.

A Double-Masked Randomized Crossover Study Comparing the Effect of Latanoprost/Timolol and Brimonidine/Timolol Fixed Combination on Intraocular Pressure and Ocular Blood Flow in Patients with Primary Open-Angle Glaucoma or Ocular Hypertension

Ocular blood flow dysregulation has been implicated in the pathogenesis of glaucoma. Whereas the effect of single antiglaucoma substances on ocular blood flow has been addressed in various experiments, evidence for fixed combinations is sparse. In the present study, we set out to compare the effects of latanoprost 0.005%/timolol 0.5% (LT) fixed combination and brimonidine 0.2%/timolol 0.5% (BT) fixed combination on intraocular pressure (IOP) and ocular blood flow. In the present study, which followed a randomized, double-masked 2-way crossover design, 16 patients with primary open-angle glaucoma and 2 patients with ocular hypertension were included. The patients underwent a 6-week treatment with LT and a 6-week treatment with BT after a washout for previous antiglaucoma medication. Optic nerve head blood flow (ONHBF) was measured using laser Doppler flowmetry; retrobulbar flow velocities were measured using color Doppler imaging in the ophthalmic artery, the central retinal artery, and the posterior ciliary arteries. IOP was measured at 8 AM, 12 PM, and 4 PM. The mean baseline IOP was 25.3±2.8 mmHg. Both drugs were equally effective in reducing IOP (LT: -35.0%±10.0%; BT: -33.6%±8.8%, P=0.463 between groups). In addition, no difference in ocular perfusion pressure was observed between the 2 treatment groups (P=0.1, between groups). Neither LT nor BT altered ONHBF (P=0.4, baseline vs. treatment) and no effect on flow velocities in the retrobulbar vessels was seen with either of the 2 treatments. In the present study, a 6-week treatment with LT or BT was equally effective in reducing IOP. In addition, none of the administered drugs induced a significant effect on ocular blood flow parameters.

Comparison of Intraocular Pressure, Blood Pressure, Ocular Perfusion Pressure and Blood Flow Fluctuations During Dorzolamide Versus Timolol Add-On Therapy in Prostaglandin Analogue Treated Glaucoma Subjects

Objective: To compare the effects of dorzolamide and timolol add-on therapy in open-angle glaucoma (OAG) patients previously treated with prostaglandin analogue (Pg), by evaluating fluctuations in the intraocular (IOP), blood (BP), ocular perfusion pressures (OPP) and retrobulbar blood flow (RBF) parameters. Methods: 35 OAG patients (35 eyes), 31 women (88.6%) age 63.3 (8.9) years were evaluated in a 3 month randomized, cross-over, single-masked study. During the experiments BP, heart rate, IOP and OPP were assessed 4 times per day (8–12–16–20 h). RBF was measured twice per day (8–20 h) using Color Doppler imaging in the ophthalmic (OA), central retinal (CRA), nasal (nSPCA) and temporal (tSPCA) posterior ciliary arteries. In each vessel, peak systolic velocity (PSV) and end-diastolic velocity (EDV) were assessed and vascular resistance (RI) calculated. Results: Both add-on therapies lowered IOP in a statistically significant manner from 15.7 ± 2.4 mmHg at latanoprost baseline to 14.9 ± 2.2 mmHg using dorzolamide (p < 0.001) and 14.2 ± 1.9 mmHg using timolol (p < 0.001). The IOP lowering effect was statistically significant at 20 h, favoring timolol as compared to dorzolamide (1.4 ± 2.4 vs. 0.2 ± 2.1 mmHg), (p < 0.05). Dorzolamide add-on therapy showed smaller IOP (2.0 ± 1.4), SPP (13.3 ± 7.9), systolic BP (13.5 ± 8.7) and diastolic BP (8.4 ± 5.4) fluctuations as compared to both latanoprost baseline or timolol add-on therapies. Higher difference between morning and evening BP was correlated to decreased evening CRA EDV in the timolol group (c = −0.41; p = 0.01). With increased MAP in the morning or evening hours, we found increased evening OA RI in timolol add-on group (c = 0.400, p = 0.02; c = 0.513, p = 0.002 accordingly). Higher MAP fluctuations were related to impaired RBF parameters during evening hours-decreased CRA EDV (c = −0.408; p = 0.01), increased CRA RI (c = 0.576; p < 0.001) and tSPCA RI (c = 0.356; p = 0.04) in the dorzolamide group and increased nSPCA RI (c = 0.351; p = 0.04) in the timolol add-on group. OPP fluctuations correlated with increased nSPCA RI (c = 0.453; p = 0.006) in the timolol group. OPP fluctuations were not related to IOP fluctuations in both add-on therapies (p < 0.05). Conclusions: Both dorzolamide and timolol add-on therapies lowered IOP in a statistically significant fashion dorzolamide add-on therapy showed lower fluctuations in IOP, SPP and BP. Higher variability of daytime OPP led to impaired RBF parameters in the evening.

Correlation of optic disc morphology and ocular perfusion parameters in patients with primary open angle glaucoma

Little information is available about the relationship between glaucomatous visual field defects, morphological changes of the optic disc and ocular blood flow. In this study, ocular blood flow parameters were correlated with parameters of optic nerve head (ONH) morphology and visual field performance in a cross-sectional study. A total of 103 patients with primary open angle glaucoma were included. Choroidal and ONH blood flow was assessed using laser Doppler flowmetry. Retinal blood velocities and retinal vessel diameters were measured with laser Doppler velocimetry and a Retinal Vessel Analyzer, respectively. To evaluate the ONH morphology, fundus photographs were taken and confocal laser scanning tomography was performed. Among all measured ocular hemodynamic parameters, the ONH blood flow was most strongly correlated to structural parameters of ONH damage and visual field loss. Reduced retinal vessel diameters were only slightly correlated with the degree of glaucomatous damage. Reduced blood flow in the ONH was associated with increasing amount of visual field defect and morphological changes of the ONH. Retinal vessel diameters were only marginally associated with glaucomatous optic nerve damage. Based on retinal vessel diameter determination alone, it is not possible to assess whether reduced retinal blood flow is causative or secondary in glaucoma.

Functional and hemodynamic parameters in glaucoma patients after trabeculectomy

Abstract Purpose To study a correlation of hemodynamic and electroretinography (ERG) parameters in patients with primary open angle glaucoma (POAG) before and after trabeculectomy. Methods 29 patients (32 eyes) with early, advanced and late stages of POAG were tested prior to surgery and at 2 months after trabeculectomy. Standard ERG methods and chromatic macular ERG were used. Ocular hemodynamics were evaluated by colour Doppler sonography. Peak systolic velocities (PSV), end‐diastolic velocities (EDV), and resistive indices (RI) of the ophthalmic artery, central retinal artery (CRA) and short posterior ciliary arteries (SPCA) were obtained. Results After surgery reduction of IOP (62.7%, p≤0.001) revealed a significant increase of amplitude values of OPs and macular ERG (p≤0.05). In early and late stages of POAG there were no significant differences in ocular blood flow parameters before and after trabeculectomy. In advanced stage the PSV and EDV in CRA were increased (p≤0.05). We found a correlation between macular ERG to red stimuli, OPs and blood flow parameters in CRA and SPCA before trabeculectomy. After surgery statistics revealed a correlation only between OPs and PSV in CRA. Conclusion The functional changes of macular area and inner retina are more common in patients with simultaneous decrease of PSV and EDV in CRA and SPCA. Retinal bioelectric activity in early and advanced stages of POAG is IOP‐dependent, and can be partially restored after IOP reduction. In contrast to ERG, the retinal blood parameters are relatively constant before and after short period of trabeculectomy.

Effect of Dorzolamide and Timolol on Ocular Pressure: Blood Flow Relationship in Patients with Primary Open-Angle Glaucoma and Ocular Hypertension

The authors have reported previously that a study population, consisting of patients with glaucoma and ocular hypertension, is characterized by an impaired association between ocular blood flow parameters and systemic blood pressure, indicative of abnormal autoregulation. Here they report on the effects of dorzolamide and timolol on ocular pressure/flow relationships to test the hypothesis that these drugs improve autoregulation. One hundred forty patients with primary open-angle glaucoma or ocular hypertension were included in a clinical trial in a controlled, randomized double-masked study in two parallel groups. Seventy patients were randomly assigned to receive timolol, and 70 patients were randomly assigned to receive dorzolamide for a 6-month period. Scanning laser Doppler flowmetry was used to measure blood flow in the temporal neuroretinal rim and the cup of the optic nerve head. Pulsatile choroidal blood flow was assessed using laser interferometric measurement of fundus pulsation amplitude. The association between blood flow parameters and systemic blood pressure was compared before and after the 6-month treatment period. Before treatment a significant association was observed between ocular blood flow parameters and systemic blood pressure in both parallel groups (r = 0.23-0.42). All regression lines between ocular hemodynamic parameters and systemic blood pressure were less steep after treatment with either dorzolamide or timolol (r = 0.03-0.24). The present study indicates that intraocular pressure reduction with timolol or dorzolamide is associated with normalization of the ocular pressure/flow relationship. Whether this is related to the beneficial effects of IOP-lowering therapy in glaucoma remains to be established. (ClinicalTrials.gov number, NCT00991822.).

Effect of systemic moxaverine on ocular blood flow in humans

A number of common eye diseases are associated with ocular perfusion abnormalities. The present study aimed to investigate whether systemically administered moxaverine improves ocular blood flow. Sixteen healthy volunteers were studied in this randomized, double-masked, placebo-controlled, two-way crossover study. Moxaverine in a dose of 150 mg was administered i.v. Ocular haemodynamic parameters were measured before and after drug administration. Retinal arterial and venous diameters were measured with a retinal vessel analyser. Retinal blood velocity was assessed using laser Doppler velocimetry and choroidal and optic nerve head blood flow was measured with laser Doppler flowmetry. Moxaverine increased choroidal blood flow (22.6 ± 27.9%), an effect which was significant versus placebo (p = 0.015). Red blood cell velocity in retinal veins tended to increase by 13.6 ± 13.3% after infusion of moxaverine, but this effect was not significant compared with placebo (p = 0.25). In the optic nerve head moxaverine also tended to increase blood flow (11.8 ± 12.7%), but, again, this effect was not significant versus placebo (p = 0.12). Neither moxaverine nor placebo had an effect on retinal arterial diameters. In retinal veins moxaverine tended to induce vasodilation (2.6 ± 2.8%) and to increase blood flow (19.6 ± 16.5%), but these effects were not significant (both p = 0.12). The present study indicates an increase in choroidal blood flow after systemic infusion of a single dose of moxaverine in healthy subjects. Further studies are warranted to investigate whether these effects are also seen after longterm treatment in patients with ocular vascular disease.

Visual Function, Optic Nerve Structure, and Ocular Blood Flow Parameters after 1 Year of Glaucoma Treatment with Fixed Combinations

To compare the effects of latanoprost/timolol (LTFC) versus dorzolamide/timolol (DTFC) fixed combinations on intraocular pressure (IOP), visual function, and retrobulbar blood flow in patients with open-angle glaucoma (OAG). This was a prospective, randomized, double masked, parallel study on 30 patients with OAG. All patients received 4 weeks of timolol treatment prior to randomization to LTFC or DTFC treatment. Measurements after randomization were taken at 1, 6, and 12 months, including arterial blood pressure; IOP; color Doppler imaging of the ophthalmic artery (OA), central retinal artery, and short posterior ciliary artery (SPCA); scanning laser polarimetry; Humphrey visual field examination; and adverse events. IOP decreased by 5.0 mmHg in the DTFC cohort (p<0.000) and 5.44 mmHg in the LTFC cohort (p=0.0001) after 12 months of treatment. No statistically significant differences in visual field or nerve fiber layer thickness were observed between the treatment groups during 12 months of therapy. Mean increase over 1 year of treatment in ocular perfusion and diastolic perfusion pressures were 10.46% and 10.67% in the DTFC group and 7.47% and 5.61% in the LTFC group, respectively. OA resistive index (RI) and SPCA RI were significantly different at the 12 months visit between the two treatment groups (p=0.05 and p=0.000, respectively): DTFC treatment showed decrease in the RI. One year of treatment with LTFC or DTFC resulted in similar IOP lowering effects as well as stable visual function and structure. The DTFC group showed lower vascular resistance in retrobulbar vessels compared to the LTFC group.

Impact of medication on ocular blood flow

Abstract Purpose Reduced ocular blood flow appears to play a role in the pathophysiology of glaucoma. Hence, there is considerable interest in drugs that are capable of improving ocular perfusion. Methods A large numer of clinical trials have been performed investigating the ocular hemodynamic effects of topical and systemic medications. Such trials used a variety of different methods to assess ocular blood flow parameters. Results When adminsitered systemically most vasodilators decrease systemic blood pressure thereby reducing ocular perfusion pressure (OPP). Only few classes of drugs have been reported to increase ocular blood flow with no or minimal effect on OPP. Among these carbonic anhydrase inhibitors and endothelin receptor anatgonists show the most prononced ocular vasodilator effects. The ocular hemodynamoic effects of topical medications is generally considered small. Conclusion When drugs are given systemically the effects on OPP have to be considered. In addition, the potentially positive effects on ocular perfusion need to be carefully weighed against the side effects. With topically administered drugs the ocular hemodynamic effects will be generally small, because the drugs reach the posterior pole of the eye in small concentrations only.

Ocular haemodynamic changes after single treatment with photodynamic therapy assessed with non‐invasive techniques

To investigate in patients with neovascular age-related macular degeneration (ARMD) the changes in ocular perfusion caused by single treatment with photodynamic therapy (PDT) by different non-invasive methods; to evaluate correlations between relative changes of ocular haemodynamic parameters after PDT among each other and compared to morphological parameters; and to assess this in relation to early changes of visual acuity. 17 consecutive patients with subfoveal choroidal neovascularization (CNV) caused by ARMD scheduled for PDT without previous PDT treatment (four patients with predominantly classic CNV and 13 patients with occult CNV). best-corrected visual acuity (before PDT, 6 and 8 weeks after PDT), fundus photography, fluorescein angiography, haemodynamic measurements with laser Doppler flowmetry (LDF), laser interferometry and ocular blood flow (OBF) tonometry (baseline and 1, 2, 6 and 8 weeks after treatment). choroidal blood flow (CHBF), fundus pulsation amplitude (FPA), pulsatile ocular blood flow (POBF), visual acuity. Changes smaller than 20% were considered clinically irrelevant. Ocular haemodynamic parameters did not change significantly in the follow-up period. Changes of haemodynamic parameters showed no correlation to treatment spot, morphological changes or visual acuity. Changes of visual acuity were comparable to results of earlier studies. Single treatment with PDT did not modify ocular blood flow parameters above 20% as assessed with different non-invasive methods.

Comparision of the effects of subtenon’s and subconjunctival anesthesia on retroorbital hemodynamics

Abstract The aim of the study was to compare retroorbital blood flow hemodynamics between subconjunctival and sub-Tenon’s anesthesia. This was a prospective, blinded study and included 80 cases. Patients were monitored and treated in the First Ophthalmology Clinic, Ataturk Training and Research Hospital, Turkey. Sub-Tenon’s anesthesia was performed in 42 cases, and subconjunctival anesthesia was performed in 38 cases. Color Doppler imaging to measure ocular blood flow parameters was performed preoperatively and 21 days after cataract operation in each case. Preoperative and postoperative values of resistivity and pulsatility indices in the ophthalmic, central retinal, and short posterior ciliary arteries were compared. Postoperative mean blood flow velocity measurements of ophthalmic artery were not statistically different between the subconjunctival anesthesia group and the sub-Tenon’s anesthesia group (49.63 ± 14.00 vs. 45.85 ± 13.41; P=0.389). Postoperative RI values were higher in the Subtenon’s anesthesia group than in the subconjunctival anesthesia group, but the difference between two groups was not statistically significant (0.81 ± 0.14 vs. 0.74 ± 0.08; P=0.079). The postoperative pulsatility index of the ophthalmic artery, RI of ophthalmic artery, pulsatility index of the central retinal artery, RI of the central retinal artery, and pulsatility index of the posterior ciliary arteries were not significantly different between the subconjunctival and sub-Tenon’s anesthesia groups. In conclusion, the study suggests that postoperative retroorbital blood flow hemodynamics are the same following sub-Tenon’s and subconjunctival anesthesia.

Diurnal fluctuation of ocular blood flow parameters in patients with primary open-angle glaucoma and healthy subjects

Background/aims:To investigate the fluctuations of ocular blood flow parameters over 13 h in patients with primary open-angle glaucoma (POAG) and in healthy eyes, and to relate these fluctuations with variations...

Effect of dual endothelin receptor blockade on ocular blood flow in patients with glaucoma and healthy subjects

PURPOSE. Several lines of evidence indicate that altered blood flow regulation may contribute to the pathogenesis of glaucomatous optic neuropathy. Recent data support the hypothesis that the endothelin system is involved in the processes that lead to vascular dysregulation in glaucoma. This study was conducted to test the hypothesis that bosentan, a dual endothelin receptor antagonist, increases ocular blood flow in patients with glaucoma. METHODS. Fourteen patients with primary open-angle glaucoma and 14 sex- and age-matched healthy volunteers were included. Both groups received bosentan 500 mg daily for 8 days. Ocular hemodynamics were assessed at baseline and on the last study day. Retinal vessel diameters and retinal red blood cell velocity were recorded with a retinal vessel analyser and laser Doppler velocimetry, respectively. Choroidal and optic nerve head blood flow were measured with laser Doppler flowmetry. RESULTS. Retinal arteries and veins showed a significant dilatation after administration of bosentan in both groups (5%‐ 8%). Retinal blood velocity and retinal blood flow increased up to 45% after administration of bosentan in both patients and healthy subjects. Administration of bosentan increased choroidal (12%‐17%) and optic nerve head blood flow (11%‐24%) in both groups. The effect of bosentan on ocular blood flow parameters was comparable between the two groups. CONCLUSIONS. The data from the present study indicate that dual inhibition of endothelin receptors increases ocular blood flow in patients with glaucoma and healthy subjects. Further studies are needed to study the dose‐response relationship of this effect and to characterize the role of endothelin receptor subtypes. (Invest Ophthalmol Vis Sci. 2009;50:358‐363) DOI: 10.1167/iovs.08-2460

Effect of Dual Endothelin Receptor Blockade on Ocular Blood Flow in Patients with Glaucoma and Healthy Subjects

Several lines of evidence indicate that altered blood flow regulation may contribute to the pathogenesis of glaucomatous optic neuropathy. Recent data support the hypothesis that the endothelin system is involved in the processes that lead to vascular dysregulation in glaucoma. This study was conducted to test the hypothesis that bosentan, a dual endothelin receptor antagonist, increases ocular blood flow in patients with glaucoma. Fourteen patients with primary open-angle glaucoma and 14 sex- and age-matched healthy volunteers were included. Both groups received bosentan 500 mg daily for 8 days. Ocular hemodynamics were assessed at baseline and on the last study day. Retinal vessel diameters and retinal red blood cell velocity were recorded with a retinal vessel analyser and laser Doppler velocimetry, respectively. Choroidal and optic nerve head blood flow were measured with laser Doppler flowmetry. Retinal arteries and veins showed a significant dilatation after administration of bosentan in both groups (+5%-8%). Retinal blood velocity and retinal blood flow increased up to +45% after administration of bosentan in both patients and healthy subjects. Administration of bosentan increased choroidal (+12%-17%) and optic nerve head blood flow (+11%-24%) in both groups. The effect of bosentan on ocular blood flow parameters was comparable between the two groups. The data from the present study indicate that dual inhibition of endothelin receptors increases ocular blood flow in patients with glaucoma and healthy subjects. Further studies are needed to study the dose-response relationship of this effect and to characterize the role of endothelin receptor subtypes.

Effect of Aging on Nocturnal Blood Flow in the Optic Nerve Head and Macula in Healthy Human Eyes

To study the effect of aging on 24-hour blood flow in the optic nerve head and macula of healthy human eyes. Fifteen older volunteers with healthy eyes (age 50 to 80 y) and 15 healthy younger volunteers (age 20 to 25 y) were housed for 1 day in a sleep laboratory. Every 2 hours, blood pressure and intraocular pressure (IOP) were measured after 5 minutes in the sitting position. Ocular perfusion pressure was calculated. Indices of blood volume, flow, and velocity in the optic nerve head and macula were measured using a scanning laser Doppler flowmeter at the same time points. Within the group of older subjects, nocturnal IOP was significantly lower than diurnal IOP. There was no significant difference in the ocular perfusion pressure between the 2 time periods. However, there were statistically significant decreases (6.8% to 16.8%) in the ocular blood flow parameters from the diurnal period to the nocturnal period. Within the group of younger subjects, nocturnal IOP was higher and nocturnal ocular perfusion pressure was lower than the corresponding diurnal values. There was no significant difference in any ocular blood flow parameter between the diurnal and nocturnal periods. Comparing the older and younger subject groups, nocturnal ocular perfusion pressure was higher in the older group. Significant diurnal-to-nocturnal decreases in blood flow occurred in the optic nerve head and macula in the older subjects, but not in the younger subjects. These diurnal-to-nocturnal change patterns in ocular blood flow were independent of the change patterns in ocular perfusion pressure.

Choroidal perfusion in eyes with untreated choroidal melanoma

Previous studies indicate that ocular blood flow is altered in eyes with choroidal melanoma. In the present study pulsatile ocular blood flow (POBF) was assessed to investigate whether there exists a correlation between tumour size and ocular blood flow parameters. Twenty-two patients with unilateral untreated choroidal melanoma were studied using two measurement techniques: POBF was measured with a pneumotonometer and local foveal fundus pulsation amplitude (FPA) by laser interferometry, and results were correlated. Tumour volume was calculated using the ellipsoidal solid model and was correlated to POBF and FPA. Levels of POBF and FPAs tended to be higher in tumour eyes compared with unaffected eyes, but the differences did not reach the level of significance. Both methods showed a high degree of correlation in unaffected eyes. In tumour eyes the correlation was slightly less pronounced. There was no correlation between tumour and POBF or FPA. Our results do not indicate choroidal hyperperfusion in patients with choroidal melanoma. The clinical usefulness of measuring POBF in tumour patients may be limited.

Strategies for improving intraindividual reproducibility in laser Doppler flowmetry measurements

Abstract Purpose: Scattering of blood flow data as assessed with laser Doppler flowmetry (LDF) in humans is a problem in many studies using this technique. We set out to reduce variability in LDF data by partializing out the effect of the total returning light level (DC) on LDF parameters in the choroid. Methods: In 20 healthy subjects choroidal blood flow was measured at different DC values using a portable confocal LDF device. To reduce scattering of data partializing out the effect of yield, defined as DC/gain, firstly a previously described method based on a third order polynomia fit using all obtained data was applied. Secondly a new method based on a linear fit obtained for each subject individually was used.In addition, these correction procedures were applied retrospectively to the data of a recent study investigating the effect of a nitric oxide (NO) synthase inhibitor on choroidal and optic nerve head blood flow parameters. Results: Both methods were successful in reducing scattering of LDF parameters in the choroid with varying baseline DC values. In addition, both methods minimized scattering of the effect of the NO synthase inhibitor on ocular blood flow parameters as analyzed retrospectively. Whereas, however, the previous approach altered the magnitude of the mean change induced by the NO synthase inhibitor to higher values, the new method preserved the originally reported effect. Conclusions: When systematic changes in DC occur after an intervention one needs to be careful in interpreting the obtained data. The approach presented here may represent an effective, easily applicable and valid way to reduce scattering of data from using LDF to assess blood flow in the posterior pole of the human eye.