Biomedical subjects

J DuPont

Publications and source records attributed to J DuPont.

11 recordsLinked to original sources

PubMed2004

Effect of laser treatment for dry age related macular degeneration on foveolar choroidal haemodynamics.

AIM: Previous studies have suggested that laser photocoagulation therapy is associated with the resolution of drusen in some age related macular degeneration (AMD) patients. The main aim of the study was to determine whether low intensity laser treatment applied according to the Complications of AMD Prevention Trial (CAPT) protocol produces changes in the choroidal circulation that may help explain the mechanism leading to the resolution of drusen material. METHODS: This ancillary study included 30 CAPT patients with bilateral drusen that were treated and followed at the University of Pennsylvania. Laser Doppler flowmetry was used to measure relative choroidal blood velocity (Ch(vel)), volume (Ch(vol)), and flow (Ch(flow)) in the centre of the fovea. Measurements were obtained through a dilated pupil in both eyes of each patient at the initial CAPT visit before laser treatment was applied in one eye. Measurements were repeated in both eyes of each subject three months later. Analysis of laser Doppler measurements was performed in a masked fashion. RESULTS: In comparison to baseline, no significant differences in Ch(vel), Ch(vol), or Ch(flow) were observed three months following the application of low intensity laser according to the CAPT protocol in the untreated and treated eyes. In comparison to the untreated eyes, no significant differences were detected in the treated eyes. Based on the variability of flow measurements in the untreated eyes, the authors estimated an 85% power to detect a 15% change in relative blood flow. CONCLUSIONS: The results suggest that large alterations in choroidal blood flow do not occur at three months after low intensity laser therapy following the CAPT protocol.

Aged↗

PubMed2000

Human retinal hemodynamics following administration of 5-isosorbide mononitrate.

PURPOSE: The purpose of this randomized double-masked cross-over study was to determine the effects of 20 mg of 5-isosorbide mononitrate (ISMO) on the retinal hemodynamics of young healthy subjects. METHODS: Monochromatic fundus photography and bidirectional laser Doppler velocimetry (BLDV) were used to determine vascular diameters (D), and blood velocity (V(max)) and flow (Q) in retinal veins, respectively. The diameter of the vein [D((vein))] at the same location where BLDV measurements were made, and the diameter of a neighboring artery [D((art) )], were determined from the fundus photographs. Measurements were carried out one and three hours after ISMO dosing, on twelve and six subjects, respectively. Mean blood pressure (BP(m)) and intraocular pressure (IOP) were also monitored, and ocular perfusion pressure (PP) was calculated. Results are expressed in percentage changes (+/- the standard error of the mean). RESULTS: On average, we observed a moderate increase of Q one hour after ISMO dosing (+8.2 +/- 5.4%), but not after placebo (+2.7 +/- 1.6%). This effect of ISMO, which displayed remarkable interindividual variability (95% confidence interval: -3.9%, +20.4%), did not attain statistical significance. D((vein)) and D((art)) were not appreciably affected. No effect was observed three hours after either ISMO or placebo dosing. PP was reduced one hour following ISMO administration, mainly as a function of reduced BP(m), although this variation was not statistically significant. IOP did not change appreciably throughout the duration of the study. CONCLUSIONS: Our findings suggest that, in contrast to the optic nerve head, in which we previously documented consistent and significant increases in blood flow following ISMO administration at both one and three hours, retinal hemodynamics are not equally responsive to a single dose of ISMO at these time points. Marked interindividual variability to the effects of this long-acting nitric oxide donor was documented one hour after administration, but not at three hours. This study further suggests that distinct vascular tissues of the ocular microcirculation respond differently to identical pharmacological challenges.

Adult↗

PubMed1999

The effect of pregnancy on retinal hemodynamics in diabetic versus nondiabetic mothers.

PURPOSE: To investigate retinal circulatory changes that occur during the third trimester of pregnancy in diabetic patients and control subjects. METHODS: Bidirectional laser Doppler velocimetry and monochromatic fundus photography were used to assess the retinal circulation in seven pregnant diabetic patients and 13 age-matched pregnant control subjects. Retinal venous diameter (D), maximum erythrocyte velocity (Vmax), and retinal volumetric blood flow rate (Q) were measured in one eye of each subject during the third trimester of pregnancy (DPREG, VmaxPREG, and QPREG, respectively). These measurements were repeated during the postpartum period for both diabetic patients (11+/-7 weeks postpartum) and control subjects (16+/-6 weeks postpartum; P = .203; DPOST, VmaxPOST, and QPOST). RESULTS: In control subjects, DPREG was significantly reduced by -4.5%+/-4.4% (mean percent difference +/-1 standard deviation; paired t test, P =.006) relative to DPOST. In diabetic women, DPREG was also significantly reduced by -8.1%+/-3.2% compared with DPOST (P = .001), a change that was significantly larger than that seen in control subjects (unpaired t test; P = .035). Compared with QPOS T, QPREG was reduced by -7.1%+/-14.2% (P = .123), in control subjects. In diabe tic women, QPREG was significantly decreased by -18.4%+/-9.3% compared with QPOST (P = .012). This reduction in QPREG was significantly greater in diabetic patients than in nondiabetic control subjects (unpaired t test, P = .040). No significant differences between VmaxPREG and VmaxPOST were observed in either diabetic patients (-3.1%+/-12.9%; P =.400) or control subjects (+1.9%+/-14.4%; P = .787). CONCLUSIONS: Retinal venous diameter is decreased during the third trimester of pregnancy in both diabetic and nondiabetic mothers. This decrease is significantly larger in diabetic than in nondiabetic mothers. In addition, we observed a reduction in retinal volumetric blood flow in diabetic patients during pregnancy that was significantly larger than that present in nondiabetic women. This fall in retinal volumetric blood flow in diabetic patients may exacerbate retinal ischemia and hypoxia and thus may be associated with the progression of diabetic retinopathy.

Adult↗

PubMed1999

Effect of isosorbide mononitrate on the human optic nerve and choroidal circulations.

AIMS: To assess the effects of the nitric oxide donor 5-isosorbide mononitrate (ISMO) on blood flow in the optic nerve head (ON flow) and choroid (Ch flow). METHODS: Laser Doppler flowmetry was used to measure ON flow and Ch flow in 12 normal subjects by aiming the laser beam at the fovea and at the temporal rim, respectively. In a double masked, randomised, crossover design, each subject received orally on separate days either 20 mg of 5-isosorbide mononitrate (ISMO) or placebo. Ch flow and ON flow were determined monocularly at baseline and 1 hour after dosing. In the last six subjects, additional measurements were obtained at 3 hours. Mean arterial blood pressure (BPm), heart rate, and intraocular pressure (IOP) were monitored, and ocular perfusion pressure (PP) was estimated. RESULTS: No significant changes in ON flow, PP, IOP, or BPm were observed following placebo. Following ISMO, ON flow increased from baseline by 19.8% (SEM 9.3%) at 1 hour (paired t test, p = 0.058) and by 33.1% (7.5%) at 3 hours (p = 0.007). Compared with the changes following placebo, statistically significant increases in ON flow were observed both at 1 (p = 0.050) and 3 hours (p = 0.041) after ISMO treatment. Compared with placebo, PP decreased significantly 1 hour after ISMO dosing (p = 0.039), mainly as a function of reduced BPm. A significant inverse correlation (R = -0.618; p = 0.032) was observed between the percentage changes in PP and ON flow 1 hour following ISMO administration, but not after placebo. No significant change in foveal Ch flow was documented. CONCLUSIONS: These results suggest that, in normal subjects, ISMO increases significantly ON flow but not Ch flow. The inverse correlation observed between PP and ON flow suggests that the same mechanism(s) responsible for systemic vasodilatation and blood pressure decrease may also cause the ON flow increase.

Adult↗

PubMed1998

Effect of aging on foveolar choroidal circulation.

OBJECTIVE: To determine the effect of aging on choroidal blood flow (ChBFlow) in the foveolar region of the normal ocular fundus. METHOD: Choroidal blood flow was determined using laser Doppler flowmetry. Twenty-nine eyes of 29 normal subjects whose ages ranged from 15 to 76 years (mean+/-SD, 42+/-18 years) were included in this study. Relative choroidal blood velocity (ChBVel), choroidal blood volume (ChBVol), and ChBFlow were determined in the foveolar region by asking the subjects to fixate on the probing laser beam. RESULTS: Significant negative correlations were observed between ChBVol and the subject's age (R=-0.52, P=.004) and between ChBFlow and the subject's age (R=-0.54, P=.003). No significant correlation was detected between ChBVel and the subject's age (R=0.07, P=.70). Significant differences were observed in ChBVol and ChBFlow between the younger subjects aged 15 to 45 years (mean+/-SD, 0.48+/-0.20 arbitrary units [AU] and 18.9+/-5.8 AU, respectively) and the older ones aged 46 to 76 years (mean+/-SD, 0.34+/-0.11 AU and 13.3+/-3.3 AU, respectively; unpaired Student t test, P=.04 and P=.007, respectively). CONCLUSION: In the subjects studied, foveolar ChBFlow decreases with age. This change is probably related to the decrease in density and diameter of the choriocapillaries that occurs with increasing age.

Adolescent↗

PubMed1998

Foveolar choroidal blood flow in age-related macular degeneration.

PURPOSE: To compare measurements of the foveolar choroidal blood circulation in subjects with nonexudative, age-related macular degeneration (AMD) with those of control subjects. METHODS: Laser Doppler flowmetry was used to assess relative choroidal blood velocity (ChBVel), volume (ChBVol), and flow (ChBFlow) in the center of the fovea. Measurements were obtained in 20 eyes of 20 subjects with 10 or more large drusen, visual acuity of 20/32 or better, and no evidence of choroidal neovascularization. Findings obtained in these subjects were compared with those of 10 eyes of 10 age- and blood pressure-matched control subjects with no large drusen. Foveolar choroidal blood flow measurements were obtained by asking the study participants to fixate on a probing laser beam. RESULTS: No significant differences in average age, blood pressure, or intraocular pressure were observed between subjects with AMD and control subjects. In subjects with AMD, average ChBVol was 0.24 +/- 0.08 (+/- 1 SD) arbitrary units (AU); this value was 33% lower than that of control subjects (0.36 +/- 0.11 AU; two-tailed, independent Student's t-test, P = 0.005). Average ChBVel, conversely, was not significantly different from normal (0.44 +/- 0.07 AU) in subjects with AMD (0.44 +/- 0.10 AU). Average ChBFlow in subjects with AMD (8.7 +/- 3.1 AU) was 37% lower than that of control subjects (13.7 +/- 3.5 AU) (P = 0.0005). Average blood flow pulsatility was 6% higher in subjects with AMD (0.71 +/- 0.15) than in control subjects (0.66 +/- 0.14), but this difference was not statistically significant (P = 0.42). CONCLUSIONS: Average ChBFlow in the nonexudative stages of AMD is lower than that of age-matched controls, and the effect is caused mainly by a decrease in ChBVol. Further studies are needed to elucidate whether decreased ChBFlow plays a role in the development of choroidal neovascularization, and whether ChBFlow measurements may help identify subjects with AMD at risk for developing choroidal neovascularization.

Aged↗

PubMed1998

Optic nerve and choroidal circulation in glaucoma.

PURPOSE: To investigate the circulation of the optic nerve head and choroid in patients with glaucoma. METHODS: Laser Doppler flowmetry was used to determine optic nerve head relative blood velocity (ONVel), volume (ONVol), and flow (ONFlow) in 19 primary open-angle glaucoma patients and 15 age-matched healthy control subjects. In each subject, determinations were obtained from four sites on the neuroretinal tissue and from the center of the cup. A mean of the ONVel, ONVol, and ONFlow for these five measurement sites were calculated for each subject and defined as ONVel5, ONVol5, and ONFlow5. Circulatory parameters were correlated with measures of disease progression such as cup-to-disc ratio and Humphrey visual field indices. Measurements of relative choroidal blood velocity, volume, and flow were also obtained from the foveola. RESULTS: In glaucoma patients, mean ONFlow5 was significantly lower than in control subjects (24%; P = 0.001; independent, two-tailed Student's t-test). This decrease was caused by a significant decrease in ONVol5 (15%; P = 0.04) and a nonsignificant decrease in ONVel5 (10%; P = 0.07). In glaucomatous eyes, mean ONFlow was significantly reduced from normal, by 28% in the inferior temporal neuroretinal rim location (P = 0.001) and by 24% in the superior temporal location (P = 0.001). Although mean ONFlow was also decreased by 33% in the cup, the difference was not statistically significant after a Bonferroni correction was applied. No significant differences from normal were observed in the superior and inferior nasal rim tissues. In glaucoma patients, ONFlow5 was significantly and inversely correlated with the corrected pattern standard deviation (R = -0.53; P = 0.02) and with the cup-to-disc ratio (R = -0.65; P = 0.002). Choroidal blood flow measurements obtained in the foveola of glaucomatous eyes showed no statistically significant differences from normal. CONCLUSIONS: ONFlow5 is reduced by approximately 24% in glaucoma patients. In the inferior temporal rim, the area in which nerve bundle defects most commonly occur, blood flow is reduced by 28%. Patients with more advanced glaucomatous damage, as detected by visual field corrected pattern standard deviation and measurement of the cup-to-disc ratio, tend to have lower ONFlow5. These results suggest a decrease in optic nerve blood flow that is correlated with functional and morphologic measures of glaucomatous progression. However, from these results we cannot conclude whether this decrease in flow has a primary role in the etiology of glaucoma or whether it is the result of the loss of neural components caused by this disease.

Adult↗

PubMed1997

Effect of chronic nitrate treatment on retinal vessel caliber in open-angle glaucoma.

PURPOSE: A recent report has suggested that nitrate therapy may delay the progression of glaucomatous damage. To investigate the mechanism that may mediate this effect, we sought to determine whether nitrate therapy is associated with retinal vasodilatation in patients with glaucoma. METHODS: Retinal venous and arterial diameters were determined from color fundus photographs of the optic nerve head obtained during a retrospective study designed to investigate any potential effects of chronic nitrate treatment on the progression of glaucomatous pathology. Fourteen eyes of 14 patients who were receiving chronic nitrate therapy for systemic diseases unrelated to glaucoma were randomly selected. Vascular measurements were compared with those of 15 eyes of 15 control patients with glaucoma who did not receive any nitrate therapy. RESULTS: In comparison with control patients, nitrate-treated patients showed significant average vasodilatation of 17% (P = .008) and 13% (P = .01) in the superior and inferior temporal retinal veins, respectively. A 5% increase in average retinal arterial diameter was also detected, but this was not statistically significant. CONCLUSION: Chronic nitrate treatment is associated with retinal venous dilatation in patients with glaucoma. Although not assessed in this study, it is possible that a protective effect of nitrates may be mediated by a vasoactive effect leading to improved perfusion of the retina and perhaps the optic nerve head, in a similar fashion to what has been observed in the circulation of the heart. Additional studies of the effect of nitrates on the ocular circulation are needed, however, to support this speculation.

Aged↗

PubMed1997

Effects of dorzolamide hydrochloride 2% on the retinal circulation.

PURPOSE: To study the effect of a single dose of topical dorzolamide hydrochloride 2%, a carbonic anhydrase inhibitor, on the retinal circulation of normal subjects. METHODS: Measurements of the effect of dorzolamide hydrochloride were performed in 20 normal subjects using bidirectional laser Doppler velocimetry and monochromatic fundus photography. In a double-masked randomized design, one eye received one drop of dorzolamide hydrochloride 2 % and the other eye one drop of placebo. Vessel diameter, maximum erythrocyte velocity and volumetric blood flow rate were measured in a main temporal vein of each eye before the drops, and then, 2 h later. RESULTS: Following treatment, intraocular pressure decreased by 12% in the dorzolamide-treated eye (p = 0.0004, paired Student's t-test) and by 4% in the placebo-treated eye, p = 0.04). No significant changes in venous diameter, maximum erythrocyte velocity, and volumetric blood flow rate were observed in the dorzolamide-treated eyes (0.6%, 2.6% and 1.4%, respectively) or the placebo-treated eyes (1%, 3.7% and 1.6%, respectively). CONCLUSIONS: A single drop of dorzolamide hydrochloride does not cause any significant change in any of the hemodynamic parameters measured. With the variability of our measurements, we have about 89% power to detect average 10% change in volumetric blood flow rate if significance testing is performed at p = 0.05 level.

Adult↗

PubMed1996

Retinal haemodynamics in patients with early diabetes mellitus.

AIMS/BACKGROUND: The retinal circulation was investigated in a group of 19 patients with insulin dependent diabetes mellitus with less than 4 years of disease duration and no evidence of diabetic retinopathy. Results of these patients were compared with those of 16 age-matched normal controls. METHODS: Venous diameter (D) was measured from monochromatic fundus photographs. Maximum erythrocyte velocity (Vmax) was assessed by bidirectional laser Doppler velocimetry in the major retinal veins of one eye of each subject. Total volumetric blood flow rate (QT) was calculated by adding the flow rates of the major retinal veins. RESULTS: Average QT was 12% larger than normal in diabetic patients (one tailed, non-paired Student's t test, p < 0.05). A statistically significant correlation was observed between QT and disease duration (r = 0.35, p < 0.04). Patients with longer disease duration tended to have somewhat larger QT. The average retinal vascular regulatory responses to hyperoxia were not significantly different from normal in diabetic patients. In these patients, however, higher blood glucose levels were associated with decreased regulatory responses to hyperoxia. CONCLUSIONS: Patients with diabetes mellitus of relatively short duration have mildly increased QT, suggesting that increased blood flow may play an early role in the development of diabetic retinal microangiopathy.

Adolescent↗

PubMed1995

Strict control of glycaemia: effects on blood flow in the large retinal vessels and in the macular microcirculation.

AIMS: The purpose of this study was to investigate the effect of instituting strict diabetic glycaemic control on the retinal macular microcirculation and to compare this effect with that observed in the main retinal veins. METHODS: In 28 insulin dependent diabetic patients with poor glycaemic control a regimen of strict diabetic control, consisting of four daily insulin injections was instituted and maintained for 6 months. Retinal haemodynamics were investigated in the macular microcirculation by the blue field simulation technique and in the major retinal veins by a combination of bidirectional laser Doppler velocimetry and monochromatic fundus photography. Progression of diabetic retinopathy was assessed from fundus photographs taken at baseline and at the end of the study. RESULTS: Institution of strict diabetic control resulted in a significant increase in leucocyte velocity in the macular circulation (p = 0.013). No significant difference in this increase was observed between eyes that showed progression (n = 8) and no progression (n = 20) of retinopathy during the study. Significant correlations were found between relative changes over time of blood flow measured in the main retinal veins and relative changes of leucocyte velocity determined in the macular microcirculation at 2 months (p = 0.008) and 6 months (p = 0.001) but not at 5 days (p = 0.49). In the eight eyes that showed progression of retinopathy, the product of leucocyte velocity and density at baseline was significantly higher than normal (p < 0.05). During the length of this study, this product was also significantly higher in the eight eyes that showed retinopathy progression than in the 20 eyes that did not show progression (p = 0.005). CONCLUSION: Our results suggest that increased flow in the macular microcirculation may be associated with progression of retinopathy, thus supporting the hypothesis that increased blood flow may play a role in the development of diabetic microangiopathy. Although there are correlations between the changes detected in the macular microcirculation and those measured in the main retinal vessels, there are also differences which need to be further investigated in order to better understand pathogenetic mechanisms.

Adolescent↗