Mean Pulsatile Ocular Blood Flow Research Articles

Pulsatile ocular blood flow in subjects with sleep apnoea syndrome

IntroductionThe aim of the study was to determine the correlation between pulsatile ocular blood flow (POBF) and sleep apnoea syndrome (SAS).Material and methodsPatients were recruited from those who underwent polysomnography in the “Sleep Unit” of the physiology department (Medical University, Lodz, Poland). A total of 52 Caucasian patients, 34 with SAS and 18 age- and gender-matched controls, were included in the study. Comprehensive ophthalmic examination included the pulsatile ocular blood flow (POBF) measurements, disc analysis with Heidelberg Retina Tomograph II and Oculus Centerfield computerized perimetry as well as the best visual acuity, a slit lamp and indirect ophthalmoscopic evaluation of anterior and posterior segments and applanation tonometry.ResultsThe observed prevalence of glaucoma in SAS patients was 5.9% (2 of 34). The mean values of POBF were 1069.21 ±235.94 µl/min in the SAS group and 1061.78 ±174.63 µl/min in the control group. The study revealed that the differences of mean POBF between the SAS patients and the control group were not statistically significant: Mann-Whitney U-test p > 0.05. No correlations were found between sleep apnoea syndrome and mean intraocular pressure (IOP), mean retinal nerve fibre layer (RNFL) thickness and visual field mean defect (MD).ConclusionsNo correlation was found between pulsatile ocular blood flow and sleep apnoea syndrome. Although some previous studies found an association between IOP, MD, RNFL thickness and sleep apnoea syndrome, our study did not confirm that. However, a high prevalence of glaucoma was found among SAS patients in Poland.

Pulsatile Ocular Blood Flow in Healthy Koreans

PurposeTo determine the normal reference range of pulsatile ocular blood flow (POBF) values in healthy Korean subjects and to find out the factors that may affect them.MethodsA total of 280 eyes of 280 normal subjects were included in this study. Best corrected visual acuity (BCVA), intraocular pressure (IOP), axial length, POBF, systemic blood pressure, and pulse rate were measured. The mean, standard deviation, range, and the 5th and 95th percentiles of POBF were calculated, and the influences of various parameters to POBF were determined by multiple regression analyses.ResultsThe mean POBF value was 766.0±221.6 µl/min in men and 1021.1±249.5 µl/min in women. The 5th and 95th percentiles for POBF values were 486.0 µl/min and 1140.0 µl/min in men and 672.0 µl/min and 1458.0 µl/min in women. The POBF values were significantly influenced by gender, mean blood pressure, pulse rate, and axial length.ConclusionsEven though the POBF values were influenced by gender, BP, and axial length, we could define the normal reference range of POBF in healthy Koreans.

Pulsatile ocular blood flow: Changes associated with scleral buckling procedures

To determine the changes in the pulse amplitude (PA) and the pulsatile ocular blood flow (POBF) after scleral buckling (SB). Retrospectively, we studied 24 patients (average age, 52 years) who had undergone SB to repair a retinal detachment in one eye. The patients were divided into two groups: those in whom SB had been performed less than 6 months earlier (n = 10), and those in whom the procedure had been performed more than 6 months previously (n = 14). In each group, the PA and the POBF were determined with a computerized tonometry system, and the values in the SB eyes were compared with those in the control fellow eyes. Within 6 months postoperatively, the mean PA in the SB eyes (0.66 +/- 0.30 mmHg) was significantly lower than that in the control eyes (1.43 +/- 0.34 mmHg; P < 0.05). The mean POBF in the SB eyes (349.5 +/- 154.1 microl/min) was also significantly lower than that in the control eyes (631.0 +/- 226.6 microl/min; P < 0.05). After more than 6 months postoperatively, there were no significant differences in the PA or the POBF between the SB eyes (1.08 +/- 0.49 mmHg and 612.4 +/- 341.2 microl/min, respectively) and the control eyes (1.50 +/- 0.51 mmHg and 589.5 +/- 278.4 microl/min, respectively). These results indicate that the choroidal blood flow decreases after SB but returns to normal levels after 6 months.

Pulsatile ocular blood flow in primary open-angle glaucoma and ocular hypertension

Purpose To compare pulsatile ocular blood flow measurements in untreated ocular hypertensive (OHT) subjects and primary open-angle glaucoma (POAG) patients. Design A prospective observational study in an institutional setting. Methods A total of 97 subjects were recruited to the study (50 ocular hypertensives, 24 glaucoma patients, and 23 normal subjects). “High-risk” OHT had intraocular pressure (IOP) > 25 mm Hg; “low-risk” OHT had IOP ≤ 25 mm Hg. Pulsatile ocular blood flow (POBF) measurements were made with a pneumotonometer in sitting, standing, and supine positions. Intraocular pressure was measured with Goldmann tonometry. Twenty-six patients were started on topical treatment to reduce intraocular pressure, and the measurements were repeated at a review visit. Results Untreated POAG patients and high-risk OHT had reduced POBF ( P < .001) and pulse volume ( P < .001) compared with both normals and low-risk OHT. Women had higher POBF than men ( P = .009, two-way analysis of variance). Subjects with pharmacologically lowered IOP had a significant increase in mean POBF (+80.9 μl/min, P = .02) and a significant reduction in mean arterial blood pressure (−11.0 mm Hg, P = .003). Postural reduction in POBF (from sitting to supine) increased and became statistically significant in POAG and OHT subjects on treatment ( P < .0001). Conclusion High-risk ocular hypertensives have reduced POBF when compared with low-risk ocular hypertensives and normals and do not differ significantly from POAG patients. Our findings support the clinical impression that ocular hypertensive subjects with IOP of over 25 mm Hg should be monitored closely and may benefit from prophylactic treatment to lower intraocular pressure.

Evaluating pulsatile ocular blood flow analysis in normal and treated glaucomatous eyes

Purpose : To evaluate pulsatile ocular blood flow (POBF) analysis in normal subjects and glaucoma patients by comparison of POBF measurements with functional (as determined by visual field [VF]) and structural (as determined by optical coherence tomography [OCT]) measures. Design : Prospective, cross-sectional study. Methods : Forty-one eyes of 24 consecutive glaucoma patients and 20 eyes of 10 healthy subjects were studied; POBF analysis was performed on all subjects at the same visit as VF testing and OCT retinal nerve fiber layer (NFL) thickness measurement. The mean results of normal and glaucomatous eyes were compared for each method. Correlation between measurements obtained with each modality and the discriminating power using receiver operator characteristic curves was tested. Results : The mean POBF (standard deviation [SD]) in the normal group was 1,010.4 (292.8) μl/min and 989.3 (305.5) μl/min in the glaucoma group ( P = .90). Significant differences between groups were found for VF mean deviation and pattern standard deviation ( P = .02, P = .004, respectively) and OCT mean NFL thickness ( P < .0001). No correlation was found between POBF parameters and intraocular pressure, VF, or OCT variables except for intraocular pressure in glaucoma group (r = −.43, P = .003). The area under the receiver operator characteristic curves was higher for VF indexes and OCT mean NFL thickness than POBF parameters for distinguishing between normal and glaucomatous eyes. Conclusions : The wide range of normal values and the low discriminating power of POBF between normal and glaucomatous eyes limits the clinical use of the device for glaucoma patients.

Gender and Age Effects on Pulsatile Ocular Blood Flow

Purpose: To examine gender and age effects on pulsatile ocular blood flow (POBF). Methods: Normal subjects, 152 females and 107 males, were separated into younger (40–50) and older (50–60) age groups. Results: For younger women, mean POBF (15.3 ± 3.7 µl/s) was significantly different (p < 0.01) than for older women (13.8 ± 3.5 µl/s), younger men (13.2 ± 3.3 µl/s), and older men (13.3 ± 3.1 µl/s). The mean POBFs for each of the latter three groups were not significantly different (p > 0.41) from one another. The four groups showed no significant differences in intraocular pressure (p > 0.07) or refraction (p > 0.46). Pulse rate for younger women was significantly higher (p < 0.05) than for the older two groups, but there were no significant pulse rate differences (p > 0.08) between other groups. POBF was not correlated with IOP (r² < 0.04), refraction (r² < 0.009) or pulse rate (r² < 0.04). Conclusion: Gender and age play an important role in POBF.

Effects of ethnic origin on pulsatile ocular blood flow

Purpose: To study the effect of ethnicity on pulsatile ocular blood flow (POBF).Methods: Eighty subjects from the staff and student population at Anglia Polytechnic University were examined. Forty subjects (20 males, 20 females) were Asian (originating from the Indian subcontinent) and 40 (20 males, 20 females) were white people. The subjects underwent a complete ophthalmic examination including refraction, slitlamp examination and biomicroscopic fundoscopy. Subjects with ocular pathology were excluded from the study. Subjects underwent POBF measurement on a randomly selected eye with an Ocular Blood Flow Analyzer (Paradigm Medical Industries, Salt Lake City, UT, USA). The Analyzer probe was mounted on a slitlamp and all measurements were performed by an experienced observer (PG).Results: The median age of the Asian subjects was 22 years (males 22 years; females 22 years) and of the white people was 24 years (males 26 years; females 23 years). The racial groups were comparable for age (Mann–Whitney U = 686.5, p = 0.27), refraction (Mann–Whitney U = 735.5, p = 0.4658) and IOP (Mann–Whitney U = 856, p = 0.5899). The mean POBF values in the Caucasian and Asian groups were 1033 µL min−1 (95% CI: 940–1125 µL min−1) and 1061 µL min−1 (95% CI: 958–1165 µL min−1), respectively. The difference in POBF between the ethnic groups did not reach statistical significance (Mann–Whitney U = 0.07, p = 0.7987). Females had a higher mean POBF than males (Mann–Whitney U = 1163; p = 0.0005) but there was no interaction with race (two‐way anovaF = 1.09; p = 0.2997).Conclusions: There was no significant difference between the mean POBF values for subjects originating from the Indian subcontinent and Caucasian subjects. The previously reported gender difference in mean POBF was confirmed. We suggest that reported differences in POBF values in different races may arise from instrumental factors.

Comparative effects of latanoprost (Xalatan) and unoprostone (Rescula) in patients with open-angle glaucoma and suspected glaucoma

PURPOSE: To compare, in paired eyes of open-angle glaucoma patients and glaucoma suspects, hydrodynamic and visual changes after 1 month of topical latanoprost in one eye and unoprostone in the other. DESIGN: Single-center, institutional randomized clinical trial. METHODS: After completing a washout period off all topical medication, 25 adults (mean age 54 ± SEM 2 years) with bilateral open-angle glaucoma or glaucoma suspect status underwent morning (8 to 10 am) and afternoon (1 to 3 pm) measurements of intraocular pressure (IOP), pulsatile ocular blood flow (POBF), contrast, sensitivity, frequency doubling technology, and Humphrey 10-2 perimetry (HVFA II) in both eyes. Each then started unoprostone 0.15% (Rescula) in one randomly assigned eye and latanoprost 0.005% (Xalatan) in the other. Unoprostone was administered at 8 am and 8 pm and latanoprost at 8 pm with placebo at 8 am, both from masked bottles. After 28 days, differences were determined for each measured variable by two-tailed paired t test. RESULTS: Starting from similar baseline IOP levels, after 1 month of treatment, the mean morning IOP values differed according to the topical agent received (16.2 ± SEM 0.6 mm Hg for latanoprost vs 17.9 ± 0.7 mm Hg for unoprostone; P = .001). These morning pressures were 2.6 mm Hg lower than baseline in the eyes receiving latanoprost ( P < .0001), and 1.6 mm Hg lower in unoprostone-treated eyes ( P = .02). Afternoon values were 3.1 ± SEM 0.6 lower than corresponding baseline in eyes receiving latanoprost, and 2.4 ± SEM 0.6 mm Hg in unoprostone-treated eyes ( P < .0001 from baseline for both medications; interdrug mean IOP difference; P = .04). Eyes receiving unoprostone showed a 1.7-db improvement in frequency doubling mean deviation ( P = .03), the only significant visual function change observed. Pulsatile ocular blood flow increased 30% relative to baseline in eyes receiving latanoprost, ( P < .0001) and 16% in eyes receiving unoprostone ( P = .05) by the morning of day 28. That afternoon, mean POBF had increased 30% ( P < .0001) relative to afternoon baseline values among eyes receiving latanoprost and 18% ( P = .03) among those receiving unoprostone (interdrug change difference, P = .05). Humphrey perimetry and contrast sensitivity remained stable with both prostanoids. CONCLUSIONS: Both latanoprost and unoprostone produced significant reductions in IOP and increases in POBF, with stable central and perimacular visual function. Latanoprost once daily produced IOP reduction and POBF increases nearly twofold greater than those obtained with unoprostone twice daily. These differences in IOP and POBF change between unoprostone and latanoprost were statistically significant.

Acute effect of latanoprost on pulsatile ocular blood flow in normal eyes

PURPOSE: To determine the effect of an acute dose of 0.005% latanoprost on intraocular pressure and pulsatile ocular blood flow in normal eyes. METHODS: Nineteen volunteers received a single dose (two drops) of latanoprost 0.005% in one eye and placebo in the fellow control eye, randomized and masked to the observer. Intraocular pressure, perfusion pressure, pulsatile ocular blood flow, and systemic circulatory parameters were measured before and 8 hours after dosing. RESULTS: The mean (± SE) intraocular pressure, perfusion pressure, and pulsatile ocular blood flow before treatment were 17 ± 1 mm Hg, 46 ± 3 mm Hg, and 13 ± 1 μl per second, respectively, in both the treated and control eyes. The mean intraocular pressure reduction was 4.9 and 2.1 mm Hg (28% and 12%) in the treated and fellow eye, respectively. The mean perfusion pressure increase was 5.6 and 2.8 mm Hg (12% and 6%) in the treated and fellow eye, respectively. The mean pulsatile ocular blood flow increase was 2.7 and 0.2 μl per second (20% and 1%) in the treated and fellow eye, respectively. The treated eye change in pulsatile ocular blood flow was not correlated to the change in perfusion pressure. Simultaneous reduction of intraocular pressure and increase or no significant change in pulsatile ocular blood flow occurred in 15 of 19 (79%) of the treated eyes. The systemic blood pressure and pulse rates remained in normal ranges over the 8-hour period. CONCLUSION: In this study, topical latanoprost significantly reduces intraocular pressure and increases ocular blood flow in normal eyes 8 hours after dosing. These effects of latanoprost may be beneficial in the management of glaucoma patients.

Effects of latanoprost and timolol-XE on hydrodynamics in the normal eye

PURPOSE: To compare the effects of latanoprost and timolol-XE on ocular pressure and perfusion in healthy adults, with respect to episcleral venous pressure. METHODS: A double-masked, placebo-controlled crossover study of weeklong bedtime treatment with one drop of drug, with placebo contralaterally, followed by a 3-week washout and alternate-drug/contralateral-placebo repeat. Intraocular pressure was measured by applanation and by pneumotonometry, providing pulsatile ocular circulatory estimates. Measurements of episcleral venous pressure were obtained (Friberg method). RESULTS: Twenty subjects participated (five men, 15 women; mean age, 39 years (range, 21 to 55 years); mean baseline intraocular pressure, 13.4 mm Hg). A greater decrease in intraocular pressure was seen among these subjects the morning after initiating treatment with latanoprost (−2.0 mm Hg; P < .0001) than with timolol-XE (−0.9 mm Hg; P = .051) (latanoprost versus timolol Δ P = .008). This ocular hypotensive effect remained significant that evening with latanoprost (−3.2 mm Hg; P < .0001) but not with timolol XE (−1.0 mm Hg; P = .2). By the morning of day 8, mean intraocular pressure remained 3.2 mm Hg below baseline with latanoprost and 2.3 mm Hg below baseline with timolol-XE ( P < .0001 for both drugs). Neither drug altered episcleral venous pressure. Among a subgroup of nine subjects with comparable intraocular pressure reductions with the two drugs, latanoprost treatment was associated with a 16.7% increase in mean pulsatile ocular blood flow ( P = .04) through the weeklong treatment interval, consistently higher than during timolol-XE treatment of the same subjects. CONCLUSION: Latanoprost caused an overnight decrease in intraocular pressure in normotensive normal eyes, and both drugs significantly reduced intraocular pressure within 1 week. Intraocular pressure remained higher than episcleral venous pressure throughout treatment with both drugs. Latanoprost was associated with enhanced pulsatile ocular perfusion not seen with timolol-XE treatment.

Pulsatile ocular blood flow in eyes with untreated choroidal melanoma.

To investigate the effect of choroidal melanoma on pulsatile ocular blood flow (POBF). Seventeen patients (10 men and 7 women) with unilateral untreated choroidal melanoma and 22 controls matched for age and sex were studied. Intraocular pressure (IOP), pulse amplitude (PA) and POBF were measured using the OBF Tonograph. In each patient, mean inter-ocular differences were analysed using the paired t-test. The correlation coefficient between tumour thickness and POBF was calculated. To assess the variation of this parameter, the coefficient of variation for three repeated readings was determined for healthy and affected eyes. In the control group, there was no significant difference between eyes in any parameter. In patients with melanoma, there was no significant difference in IOP and PA between affected and unaffected eyes. Mean POBF was significantly higher in affected eyes (1040 microliters min-1) than unaffected eyes (876 microliters min-1) (p = 0.003). There was no correlation between tumour thickness and absolute POBF (r = -0.24) or between tumour thickness and inter-ocular difference in POBF between affected and unaffected eyes (r = -0.17). Mean coefficient of variation of three repeated readings of POBF was 7.76% in healthy eyes and 8.97% in affected eyes. These findings suggest a high tumour blood flow or a global increase in choroidal blood flow in the presence of melanoma. POBF measurement may be useful in the clinical assessment of eyes with choroidal melanoma.

Reproducibility of Pulsatile Ocular Blood Flow Measurements

Langham adapted the pneumotonometer to provide a waveform of the ocular pulse and using the heart rate derived values for pulsatile ocular blood flow. We have used a new pneumotonometer linked to an ocular blood flow system that has addressed several of the problems encountered with the Langham technique. The reproducibility of this new method was assessed by measuring pulsatile ocular blood flow (mul/min) five times on one eye of 20 normal healthy volunteers (mean age 40 years; range 26-62) at one examination session. The test was conducted in the sitting position with the pneumotonometer probe mounted on a slit-lamp microscope. The mean pulsatile ocular blood flow was 633 +/- 180 mu/min. Statistical analysis using the intraclass correlation method showed there were no significant differences due to sessions for five recordings (p = 0.15) or, after excluding the two most extreme values, for three recordings (p = 0.49). There was no correlation noted between pulsatile ocular blood flow and age in a larger group (n = 49) of normal volunteers (mean age 61 years; range 26-72). We conclude that pulsatile ocular blood flow measurements with this new instrument are reproducible and may be applied to blood flow studies in ocular hypertension and glaucoma.

The effect of increased intraocular pressure on pulsatile ocular blood flow in low tension glaucoma

In the present study the relationship between intraocular pressure (IOP) and pulsatile ocular blood flow (POBF) in low tension glaucoma (LTG) has been investigated. The POBF was measured using the Ocular Blood Flow system of Langham in undisturbed eyes and repeated at IOP increments of about 5 and 10 mmHg in 20 patients affected with bilateral LTG and in 25 healthy subjects matched for age, IOP, refractive error, arterial blood pressure and heart rate. The POBFs were 740.1 (SD 58.83) and 667 (SD 108) microliters/minute (μl/min) in the control and LTG groups, respectively, and statistically significantly different. The POBFs at an IOP increased by 5 mmHg were 658.1 (SD 60.2) and 457.3 (SD 74.8) μl/min in the control and LTG groups, respectively; in the control group the mean POBF at an IOP increment of 10 mmHg was 552.1 μl/min (SD 66.9), and in the LTG group was 317.7 μl/min (SD 85.2). Statistical analysis of the data showed a significant difference of POBFs in the two groups either at an IOP increment of 5 or 10 mmHg (p < 0.0001). The substantial decrease of POBF with increased IOP in LTG eyes compared with normals shows an altered response of the vascular system in LTG. These findings are probably consistent with a lack of the myogenic autoregulation in reply to IOP-induced modifications of the perfusion pressure.

Factors influencing the ocular pulse — the heart rate

Using pneumotonometry combined with a Langham ocular blood-flow system, measurements of pulsatile ocular blood flow (POBF) were performed in eight ocular normotensive patients with implanted cardiac pacemakers, with the subjects assuming both the erect and the supine postures. Sequential measurements of POBF were made at pre-set values of heart rate over the physiological range between 60 and 120 beats/min at intervals of 10 beats/min. With patients in the supine position, measurements of cardiac output and stroke volume indices were also recorded by impedance cardiography. The mean pulse amplitude of the intraocular pressure (the ocular pulse) decreased as heart rate increased, and this change was statistically significant in both postures according to repeated-measures analysis of variance (erect: f = 18.7, P less than 0.0001; supine: f = 18.8, P less than 0.0001). As measured in supine patients following an increase in heart rate, the pulse amplitude decreased in parallel with a decline in stroke volume index (f = 18.8, P less than 0.0001). Up to a level of 90 beats/min, the mean POBF increased with heart rate, but it declined above this rate in both erect and supine postures. At all heart rates, intraocular pressure was higher when subjects were supine than when they stood erect (f = 4.3, P less than 0.001). At lower heart rates of 70 and 80 beats/min, ocular pulse volume and POBF were significantly lower in supine patients than in erect subjects (70 beats/min: t = 3.89, P less than 0.01 vs; t = 3.87, P less than 0.01; 80 beats/min: t = 2.85, P less than 0.05 vs; t = 2.87, P less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)