Pulsatile Ocular Blood Flow Values Research Articles

Evaluation of the Effect of Hypercapnia on Vascular Function in Normal Tension Glaucoma.

Introduction. Altered ocular perfusion and vascular dysregulation have been reported in glaucoma. The aim of this paper was to evaluate the vascular response to a hypercapnic stimulus. Methods. Twenty normal tension glaucoma (NTG) patients and eighteen age- and gender-matched controls had pulsatile ocular blood flow (POBF) measurements, systemic cardiovascular assessment, and laser Doppler digital blood flow (DBF) assessed. Measurements were taken at baseline, after 10-minutes rest, in the stable sitting and supine positions and following induction and stabilization of hypercapnia, which induced a 15% increase in end-tidal pCO2. The POBF response to hypercapnia was divided into high (>20%) and low responders (<20%). Results. 65% of NTG patients had a greater than 41% increase in POBF following CO2 rebreathing (high responders). These high responders had a lower baseline POBF, lower baseline DBF, and a greater DBF response to thermal stimulus. Conclusion. NTG patients that have a greater than 20% increase in POBF after a hypercapnic stimulus have lower baseline POBF and DBF values. This suggests that there is impaired regulation of blood flow in a significant subgroup of NTG patients. This observation may reflect a generalised dysfunction of the vascular endothelium.

Pulsatile ocular blood flow changes after panretinal photocoagulation treatment in patients with proliferative diabetic retinopathy

To prospectively assess the effects of panretinal photocoagulation (PRP) treatment on pulsatile ocular blood flow (POBF) in patients with proliferative diabetic retinopathy (PDRP). The study included 40 eyes with PDRP in 27 patients. The PRP treatments were completed in 3 sessions with 3-week intervals. The intraocular pressure (IOP), pulse amplitude (PA), pulse volume (PV), and POBF changes that arose during the sessions were recorded using a blood flow analyzer. The average age of the patients was 57.37 ± 11.14 years. The pre-PRP basal IOP, PA, PV, and POBF values were 20.44 ± 4.13 mmHg, 4.23 ± 1.73 mmHg, 6.89 ± 2.28 μL, and 21.86 ± 5.83 μL/s, respectively. One month after the completion of the PRP sessions, the values were 18.49 ± 4.44 mmHg, 2.78 ± 1.13 mmHg, 5.27 ± 2.08 μL, and 15.89 ± 5.05 μL/s, respectively, and the differences were significant (P = 0.001, P < 0.0001, P < 0.0001, and P < 0.0001, respectively). PRP treatment reduces the choroidal blood flow and consequently causes significant decreases in IOP, PA, PV, and POBE .

Effects of phacoemulsification surgery on ocular hemodynamics.

To evaluate the possible effects of phacoemulsification cataract surgery on ocular hemodynamics. In this prospective study, intraocular pressure (IOP), pulsatile ocular blood flow (POBF), and ocular pulse amplitude (OPA) were measured pre-operatively (baseline) and at 1 week and 3 weeks postoperation in 52 eyes of 26 patients (mean age 63.15±10.25 years) scheduled for unilateral phacoemulsification cataract surgery with intraocular lens implantation. In all of the eyes, a blood flow analyzer (Paradigm DICON; Paradigm Medical Industries Inc.; USA) was used to obtain measurements of IOP, POBF, and OPA. The data obtained from operated eyes were compared statistically to untreated fellow phakic eyes of the patients. For operated eyes, the mean baseline IOP, POBF, and OPA values were 15.9±4.64mmHg, 17.41±4.84µL/s, and 2.91±1.12mmHg, respectively. The IOP, POBF, and OPA values were 17.19±4.34mmHg, 17.56±6.46µL/s, and 3.12±1.1mmHg, respectively, in the nonoperated control eyes. Statistically significant differences from baseline measurements were not observed 1 week and 3 weeks postoperation for the operated or nonoperated eyes. There were also no statistically significant differences in any measurements between the operated and nonoperated eyes in all the examination periods (P>0.05 for all). Uncomplicated phacoemulsification surgery does not affect ocular hemodynamics in normotensive eyes with cataracts.

Correlation Among Choroidal, Parapapillary, and Retrobulbar Vascular Parameters in Glaucoma

To study and compare the correlation among choroidal, parapapillary, and retrobulbar vascular parameters in healthy subjects, glaucoma suspects, and open-angle glaucoma (OAG) patients. Prospective observational clinical study. The study included one randomly selected eye from 21 normal subjects, 30 glaucoma suspects based on optic disc appearance, and 22 OAG patients. The pulsatile ocular blood flow (POBF), a measure of choroidal blood flow, was assessed using ocular blood flow analyzer whereas parapapillary blood flow and blood velocity of retrobulbar blood vessels were measured using scanning laser Doppler flowmetry and color Doppler imaging, respectively. All vascular parameters along with blood pressure and intraocular pressure measurements were obtained within a 2-hour period. Univariate regression analyses were used to evaluate the correlation of POBF values with parapapillary blood flow values, retrobulbar blood flow velocities, and resistive index, which represents vascular resistance, in each group. Two multiple linear regression models were created based on results of univariate analyses and included POBF, mean parapapillary blood flow, age, and mean ocular perfusion pressure; and POBF, temporal short posterior ciliary artery resistive index, age, and mean ocular perfusion pressure. POBF was significantly associated with parapapillary blood flow (r2 = 0.54; P < .001, positive correlation) and temporal short posterior ciliary artery resistive index (r2 = 0.39; P < .001, negative correlation) in normal subjects. Results were consistent when corrected for age, intraocular pressure, and blood pressure parameters. POBF values did not correlate with parapapillary blood flow values or temporal short posterior ciliary artery resistive index in glaucoma suspects or OAG patients. The relationships of POBF with parapapillary blood flow and calculated retrobulbar vascular resistance differs among normal subjects, glaucoma suspects, and OAG patients. This provides further evidence of vascular dysregulation in OAG.

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.

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 in asymmetric age-related macular degeneration

Ocular perfusion abnormalities have been proposed in the pathogenesis of age-related macular degeneration (AMD) with differences in pulsatile ocular blood flow (POBF) in eyes with asymmetric AMD in Japanese and Taiwanese patients. The purpose of our study was to observe POBF difference in the fellow eyes of Caucasians with asymmetric AMD. This was a cross-sectional study comparing POBF in three groups of patients with asymmetric AMD in the fellow eyes: Group 1 (n=21) with drusen and active choroidal neovascularisation (CNV); Group 2 (n=18) with drusen and disciform scar; Group 3 (n=8) with CNV and disciform scar. The POBF was adjusted for intraocular pressure (IOP), pulse rate (PR), and axial length using multiple regression analysis. Generalised estimation equation model was used to include both eyes in each group. The geometric mean (95% confidence interval) POBF values were as follows: Group 1 with drusen 1097.9 microl/min (957.0, 1259.7) in one eye and the fellow eye with CNV 1090.1 microl/min (932.3, 1274.7); Group 2 with drusen 946.0 microl/min (794.2, 1126.7) and disciform scar 966.2 microll/min (780.3, 1196.4); Group 3 with CNV 877.1 microl/min (628.3, 1224.6) and disciform scar 767.2 microl/min (530.5, 1109.7). Adjusting for differences in axial length, pulse rate and intraocular pressure, no statistically significant difference in POBF was found between fellow eyes in the same subject. POBF is not different between fellow eyes of Caucasian patients with asymmetric AMD.

Repeatability and Effects of Sequential Measurements with POBF Tonograph

(1) To investigate the effect of performing sequential measurements using a Pulsatile Ocular Blood Flow (POBF) Tonograph on POBF and intraocular pressure (IOP) measurements; (2) to determine any effect on IOP caused by performing POBF measurements on the fellow eye; and (3) to assess repeatability of measurements obtained using the POBF Tonograph. Forty-six normal adult subjects (13 men, 33 women; age range, 18 to 55 years) took part in the present study. Twenty-one subjects underwent sequential measurements with a POBF Tonograph on five different occasions with five different time intervals (1, 2, 5, 10, and 15 minutes) between recordings. Twenty subjects underwent a baseline measurement on one eye with the POBF Tonograph, followed by repeat measurements in both eyes after 15 minutes. An additional 25 subjects underwent sequential measurements on the same eye with an interval of 15 minutes between readings. The intraclass correlation coefficient and Bland-Altman plots were used to assess repeatability of the instrument for all 46 subjects for the 15-minute time interval. In all the groups, repeated measurement resulted in a lower recorded IOP. A multivariate analysis of variance indicated that there was a significant decrease in IOP when measurements were repeated within 15 minutes (p=0.024), but there was no significant change in the POBF values (p=0.76). The recorded IOP was significantly lower when sequential measurements were performed with an interval of 1 minute (p <0.01) compared with longer time intervals. The decrease in IOP between baseline and the repeat measurement was significantly greater in the 1-minute interval group compared with the 15-minute interval group (p <0.005). There was no significant difference in POBF values between the baseline and repeat measurements in any group. There was no significant change in IOP induced by a single measurement on the fellow eye (p >0.05). The intraclass correlation coefficient value indicated good agreement between the values of the baseline and repeat measurements using the POBF Tonograph but had wide upper and lower limits of agreement. If IOP measurements have to be repeated using the POBF Tonograph, they are best done after an interval of at least 2 minutes and preferably after 15 minutes. Use of the POBF Tonograph had no significant immediate effect on the IOP or POBF values obtained from a fellow eye.

Beneficial effects of small-incision cataract surgery in patients demonstrating reduced ocular blood flow characteristics.

To investigate intraocular pressure (IOP) and ocular haemodynamics following small incision cataract surgery. Systemic and ocular haemodynamics, and IOP, were measured pre-operatively and 1 month post-operatively, in 25 eyes of 25 patients (mean age 72.6+/-7.9 years) scheduled for small incision cataract surgery and intraocular lens implantation; these values were compared to an untreated age-matched healthy group (n=25, mean age 72.3+/-5.0 years). For each eye, the Ocular Blood Flow Analyser (OBFA, Paradigm Inc., UT, USA) was used to obtain measurements of IOP, pulsatile ocular blood flow (POBF), pulse volume (PV), ocular pulse amplitude (PA), and pulse rate (PR). Systemic blood pressure measurements were obtained at each visit. Pre- and post-operative values for the cataract group were compared using repeated measures analysis of variance, and compared to the normal group using analysis of variance. Pre-operatively, IOP was significantly higher in the cataract group compared to the age-matched normal control group (P<0.001). Cataract surgery resulted in a significant 16.7% reduction in IOP (P=0.001). Consequently, the post-operative IOP in the cataract group was similar to that of the normal group (P>0.05). Both pre- and post-operative POBF and PV values for the cataract group were significantly lower than for the normal age-matched group (P<0.0125). Small incision cataract surgery led to an 8.3% post-operative increase in POBF (P=0.0118) and 15.5% increase in PV (P<0.001). No changes in PA or PR were evident. These data suggest that cataract patients exhibit higher IOP and reduced ocular perfusion characteristics compared to an age-matched normal healthy group. Following cataract surgery, IOP reduced and ocular pulsatility improved.

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.

Pulsatile ocular blood flow measurements in healthy Asian eyes: reference values for an Indian population

Purpose: To investigate pulsatile ocular blood flow (POBF) in a healthy Indian population and use the data derived as reference values.Methods: Two hundred and fifty‐two healthy subjects (121 males, 131 females) underwent intraocular pressure and POBF measurement with the Ocular Blood Flow Analyzer (Paradigm Medical Industries, Salt Lake City, UT, USA and formerly the POBF Tonograph). Before POBF measurement, subjects underwent a complete ophthalmic examination including refraction, slitlamp examination and biomicroscopic fundoscopy and Goldmann applanation tonometry (GAT). Subjects with ocular pathology were excluded from the study. Median age was 29 years (male median 32 years, female median 27 years).Results: Average POBF in males was found to be 1052 µL min−1 (95% CI: 988–1116 µL min−1) and in females to be 1293 µL min−1 (95% CI: 1222–1364 µL min−1). Median age was significantly different between males and females (Mann–Whitney U = 6685; p = 0.0311) but POBF was found to be independent of age in both sexes. As a group, mean refractive error influenced POBF (Kendall's τ = 0.24; p = 0.0017).Conclusions: Pulsatile ocular blood flow values in Indians appear to be higher than reported in studies conducted on other racial groups. The reasons for this difference could be instrumental or anatomical (i.e axial length, ocular rigidity). Care should be taken in deriving normative data using the Ocular Blood Flow Analyzer in mixed race groups.

The pulsatile ocular blood flow behaviour in open angle glaucoma patients after replacing timolol therapy with timolol and dorzolamide fixed combination: preliminary study.

The role of ocular perfusion in the pathogenesis of primary open angle glaucoma (POAG) is increasingly discussed. At present topical beta-blockers are the most common treatment in glaucoma but almost half the patients on this topical beta-blocker treatment require an adjunct therapy to control the glaucomatous damage progression (Centofanti et al. 1999). Dorzolamide, a topical CA inhibitor, is one of the drugs most used in addition to beta-blocker therapy. This drug inhibits CA-ll isoenzyme, which plays an important role in the aqueous humour production in humans. Topically applied, dorzolamide increases retinal blood flow velocity in normal tension glaucoma patients (Sugrue 2000), enhancing CO2 concentration in ocular tissues. Scanning laser ophthalmoscopy demonstrated how dorzolamide accelerates blood velocity in the retinal and superficial optic nerve head without an apparent effect upon retrobulbar haemodynamics in healthy eyes (Harris et al. 1996). Moreover, dorzolamide accelerates retinal arteriovenous passage time of the fluorescein dye at constant retinal arterial and venous diameters, but failed to change flow velocities in any retrobulbar vessel in normal tension glaucoma patients (Harris et al. 1999). The aim of this study is to evaluate the pulsatile ocular blood flow (POBF) behaviour after adding topical anhydrase inhibitor dorzolamide in POAG patients in treatment with timolol 0.5% twice daily. Measurements of POBF, ocular pulse amplitude (PA) and intraocular pressure (IOP) were obtained by an ocular blood flow tonograph (Ocular Blood Flow System, OBF Laboratories, UK) in 12 POAG patients, 6 males and 6 females, mean age 67 years (aged between 59 and 75 years). with a well-controlled IOP using a timolol 0.5% twice-daily monotherapy. Heart rate, systolic and diastolic blood pressures were also measured at brachial artery. The first measurements were performed during the timolol 0.5% therapy before morning drop instillation (timolol trough) and 2 h after instillation (timolol peak). The second measurements were made after 2 weeks of timolol–dorzolamide fixed combination therapy and again before and after 2 h from the instillation (fixed combination trough and peak). A two-tailed paired Student's t-test was used to compare the timolol group to the fixed-combination group; P < 0.05 is considered significant. Data obtained at trough and peak during timolol monotherapy were compared to data, respectively, obtained at trough and peak during fixed combination therapy. We found a statistically significant IOP reduction at timolol peak compared to timolol trough (19.5 ± 3.1–17.9 ± 3.0 mmHg, −8.6%, P < 0.05, Table 1) and a statistically significant POBF increase at fixed combination peak compared to timolol peak (705.3 ± 234–769.0 ± 289 µl/min, + 8.7%, P < 0.05, Table 2). Other variables examined did not show any statistically significant change. In this study we found no statistically significant differences in IOP reduction between timolol 0.5% monotherapy and timolol–dorzolamide fixed combination therapy either at trough or at peak. The addition of dorzolamide to timolol monotherapy brought about an increase of POBF values which may be attributed to a direct action of the topical anhydrase inhibitor independently of IOP changes. The increasing of POBF without any statistical significant change of systemic blood pressure and heart rate leads to these variables not being considered as possible factors responsible for ocular perfusion improvement. Studies have shown that timolol–dorzolamide fixed combination efficacy in reducing IOP is completely comparable to the same combination given separately (Sugrue 2000) (not fixed). The advantage is a reduction in the number of daily instillations (from 4 to 2) associated with improved patient compliance. Therefore our results confirm the valid effect of dorzolamide action on ocular blood flow in POAG patients.

The Influence of Sex Difference in Measurements with the Langham Ocular Blood Flow System

Purpose: To assess sex difference and parameters possibly accounting for such a difference in healthy subjects evaluated by means of the Langham Ocular Blood Flow (OBF) System. Methods: Pulse amplitude of intraocular pressure (IOP) and pulsatile ocular blood flow (POBF) as measured with the Langham OBF System were assessed in 86 healthy men and 69 healthy women. Results: Compared to men, women showed higher POBF (mean ± SD: 722.6 ± 152.8 versus 647.8 ± 164.9 μL/min; P = .0056) and pulse amplitude (mean ± SD: 2.3 ± 0.7 versus 2.0 ± 0.6 mm Hg; P = .0043) values. Sex difference was still significant after correcting for age, refraction, blood pressure, IOP, and pulse rate. Pulse amplitude correlated negatively with pulse rate, and POBF correlated negatively with IOP. Women had higher readings in pulse amplitude and POBF, even after correcting for age, refraction, IOP, blood pressure, and pulse rate. Conclusions: While using the Langham OBF System, one needs to be aware of sex difference that is independent of other hemodynamic parameters. How the observed difference in POBF is related to ocular blood flow, and how it might influence the preponderance of various ocular diseases in men or women remains to be clarified.

Sildenafil increases ocular perfusion.

Our goal was to determine whether visual system responses to sildenafil accompany shifts in ocular perfusion. The human choroid, which supports the metabolic function of the outer retina, is an erectile tissue, analogous in many respects to the corpus cavenosum. Right eyes of 12 normal adults were evaluated before and 2 h after 50 mg oral dose of sildenafil. Pulsatile ocular blood flow (POBF), intraocular pressure (IOP), Heidelberg retinal flowmetry (HRT), 4.26 cpd, 7.5 Hz temporally-modulated contrast sensitivity (CS), full-threshold C-20 frequency doubling technology (FDT) perimetry, and blood pressure (BP) were measured. POBF (+29.4%; p > 0.016) and CS (+33.6%; p > 0.014%) increased within 110 (+/-7.7) minutes after sildenafil administration. No subject demonstrated decreases in either variable. HRF flow values increase among 7 of the 9 eyes producing stable scans (+8.2%; p > 0.1). FDT values did not change significantly, nor did systemic pulse amplitude or mean IOP. Since IOP and systemic pulse amplitude both remained stable after sildenafil administration, while POBF values increased to a level nearly one third greater than baseline. It appears sildenafil can induce intrinsic change in the choroidal vasculature, with an apparently positive impact on pericentral contrast sensitivity. This effect may be of clinical utility.

Pulsatile ocular blood flow in diabetic retinopathy.

To assess circulatory properties of eyes with progressive stages of diabetic retinopathy. The intraocular pressure, pulse amplitude (PA) and pulsatile ocular blood flow (POBF) were measured with a pneumatonometer (OBF Labs UK Ltd). The eyes were grouped: (a) normal control, n = 26, (b) diabetes with no observable diabetic retinopathy (NDR), n = 18, (c) mild to moderate non-proliferative diabetic retinopathy (NPDR), n = 20, and (d) very severe pre-proliferative and proliferative diabetic retinopathy (PPDR/PDR), n = 12. The PA and POBF values were lower than normal values in the earliest stage (NDR). The POBF increased but was still below normal levels at the NPDR stage, and then increased to an above normal level in the PPDR/PDR stage of diabetic retinopathy. The PA was at normal levels in these later two stages. An initial decrease in pulsatile ocular blood flow is present with the onset of diabetes where no diabetic retinopathy has yet occurred. Subsequently, the pulsatile ocular blood flow increases with the severity of the retinopathy.

Pulsatile Ocular Blood Flow and Intraocular Pressure During Retrobulbar Injection of Lignocaine

To assess the influence of adrenaline and hyaluronidase on pulsatile ocular blood flow and intraocular pressure changes during retrobulbar anesthesia. Patients undergoing cataract surgery under local anesthesia received a 5-mL retrobulbar injection of lignocaine with either adrenaline, hyaluronidase, or no addition. Continuous pneumotonometry was performed using the OBF tonograph (OBF Labs, Chippenham, UK), which automatically derives pulsatile ocular blood flow values. Measurements were taken before and one minute after injection, and changes were compared between groups to evaluate the effects of changing the constituents of the injection. There was a marked decrease in pulsatile ocular blood flow during injection in all groups. In the group receiving lignocaine with hyaluronidase, the decrease in pulsatile ocular blood flow (mean -141 microL/min) was significantly less than in either the group receiving lignocaine and adrenaline (mean -249 microL/min) or the group receiving lignocaine alone (mean -245 microL/min). There was no significant change in intraocular pressure in any group. Hyaluronidase appears to lessen the reduction in pulsatile ocular blood flow. Injection volumes of 5 mL need not cause significant intraocular pressure change.

Pulsatile ocular blood flow investigation in asymmetric normal tension glaucoma and normal subjects

AIMSThis study was designed to investigate pulsatile ocular blood flow (POBF) in normal tension glaucoma (NTG) patients and in normal controls. NTG patients with unilateral field loss were evaluated to...

Pulsatile Ocular Blood Flow Measurements in Healthy Eyes

To determine the reproducibility and the normal reference range of pulsatile ocular blood flow (POBF) values in healthy subjects using the Ocular Blood Flow Tonograph (OBF Laboratories, UK Ltd., Wiltshire, England). Pulsatile ocular blood flow was measured in one eye of each of 83 patients. Coefficient of reliability was determined by calculation of intraclass correlation coefficient via one-way analysis of variance. Mean difference between measurements was calculated for bias and first exposure effects. Pulsatile ocular blood flow from 163 healthy individuals were analyzed to determine the distribution, mean, standard deviation (SD), range, and the 5th and 95th percentile values. The influence of age, blood pressure, pulse rate, and intraocular pressure on pulsatile ocular blood flow was determined by regression analysis. Reliability coefficient for pulsatile ocular blood flow values ranging from 290 microliters/min to 2,196 microliters/min was 0.92. Variation in bias and first exposure effect were not significant. Pulsatile ocular blood flow values were normally distributed. Mean values were 669.90 +/- 233.0 microliters/min in men and 841.90 +/- 254.6 microliters/min in women. Fifth and ninety-fifth percentile values were 364.75 microliters/min and 1,266.10 microliters/min in men and 397.18 microliters/min and 1,346.10 microliters/min in women. Pulsatile ocular blood flow was significantly influenced by pulse rate. This study confirms the reliability of the Ocular Blood Flow Tonograph in repeated measurements of POBF within individuals over short time intervals. The high interindividual variation in POBF may invalidate comparison of POBF between individuals, and the wide range of normal values may limit the value of using a low POBF as a possible indicator of disease.

Visual and blood flow responses in low-tension glaucoma

Low or normal-tension glaucoma (NTG) is a rare clinical condition characterized by a glaucomatous cupping of the optic disk associated with the appearance of typical visual field defects, without ocular hypertension. According to several authors, NTG accounts for 5–15% of primary open angle glaucomas (POAG). In our open study we obtained a complete documentation of clinical and instrumental data — tonometric curve, computerized perimetry, pattern electroretinogram, pulsatile ocular blood flow (POBF) and retinography — on 10 consecutive patients (18 eyes) affected by NTG. We found that the NTG patients were similar to the controls as regards arterial systemic pressure and heart rate, but that POBF values were lower in the NTG patients.

Ocular blood flow changes in cluster headache and chronic paroxysmal hemicrania.

Intraocular pressure and pulsatile ocular blood flow were recorded during and between attacks in patients suffering from cluster headache (n = 18) or chronic paroxysmal hemicrania (n = 7). Similarities, as well as significant differences, were observed between the two groups of patients, pointing to fundamental differences between the two disorders with regard to pathophysiology. Compared with healthy controls, the cluster headache patients demonstrated low pulsatile ocular blood flow values between attacks, with an increase to normal levels during pain. The chronic paroxysmal hemicrania patients, however, had normal values between attacks with a marked and significant increase to high values during attacks.