Search PubMed⌕ Search

Biomedical subjects

J E Grunwald

Publications and source records attributed to J E Grunwald.

At least 19 recordsLinked to original sources
PubMed2000

No clinically important effects on intraocular pressure after short-term administration of sildenafil citrate (Viagra).

PURPOSE: To assess the short-term effects of sildenafil citrate on intraocular pressure in healthy male volunteers and participants in clinical trials. METHODS: Intraocular pressure and pupil diameter were measured in two placebo-controlled studies. Oral doses of sildenafil citrate (VIAGRA; Pfizer Inc, New York, New York) ranged from 10 mg to 150 mg. RESULTS: No major changes in intraocular pressure or pupillometry were detected at any time (1.0-24 hours) after administration of sildenafil. Additionally, of 36 subjects with a medical history of increased intraocular pressure in the sildenafil safety database, none were reported to have a clinically significant increase of their intraocular pressure. During clinical trials, two glaucoma cases were listed as serious adverse events, but were not considered treatment related. CONCLUSION: No clinical abnormalities were observed in intraocular pressure or pupil diameter in subjects receiving sildenafil. Currently, no evidence suggests that long-term treatment with sildenafil has an effect on intraocular pressure or is associated with the development or worsening of glaucoma.

3',5'-Cyclic-GMP Phosphodiesterases↗
PubMed2000

One-year outcomes of panretinal photocoagulation in proliferative diabetic retinopathy.

PURPOSE: To describe the clinical features and complications of diabetic retinopathy, visual acuity, and number of repeat treatments after panretinal photocoagulation for proliferative diabetic retinopathy in a tertiary care center. METHODS: A cohort study was conducted with data collection from medical records of patients undergoing panretinal photocoagulation between 1985 and 1995 at the Scheie Eye Institute; 297 eyes of 186 patients were eligible for study. RESULTS: The presence of neovascularization of the disk at baseline, an earlier onset of diabetes, and a shorter duration of disease before panretinal photocoagulation were the strongest risk factors for needing an additional panretinal photocoagulation treatment. Sixty-two percent of eyes with poor visual acuity (< or =20/200) at baseline still had poor visual acuity at 1 year, and 76% with good visual acuity (> or =20/40) at baseline maintained good visual acuity at 1 year. Poor vision at baseline was the only risk factor for having poor vision at 1 year. Vitreous hemorrhage was present in 44% of eyes at baseline. New vitreous hemorrhage developed in 37% of eyes during the first year after panretinal photocoagulation. A traction retinal detachment was present in 4% of eyes at baseline and newly developed in 6% of eyes during follow-up. A repeat panretinal photocoagulation treatment was performed in 39% of eyes after initial treatment. A vitrectomy was performed in 10% of eyes from baseline through the 1-year follow-up visit. CONCLUSIONS: The data from this study are useful for counseling patients with respect to likely visual outcome, possibility of major complications from proliferative diabetic retinopathy, and the chance of undergoing additional laser treatment after panretinal photocoagulation.

Adolescent↗
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

Optic nerve blood flow in glaucoma: effect of systemic hypertension.

PURPOSE: To investigate optic nerve head blood flow in patients with glaucoma and to assess the effect of systemic hypertension. METHODS: This study included 24 eyes of 24 patients with primary open-angle glaucoma. Eleven of these patients had a history of systemic hypertension. Results in patients with glaucoma were compared with those of 13 eyes of 13 age-matched normal controls. Determinations of relative optic nerve head blood velocity, volume, and flow were obtained with laser Doppler flowmetry in the superotemporal and inferotemporal neuroretinal rim and also in the cup. Means of the velocity, volume, and flow of these three measurement sites were calculated for each subject. RESULTS: Mean overall optic nerve head blood flow was 29% lower in glaucoma patients than in normal controls (t test, P < .001). This decrease in flow was mainly caused by a decrease of 23% in mean blood velocity (P < .001). Mean flow in glaucoma patients without systemic hypertension was 26% lower than that of glaucoma patients with hypertension (Tukey honest significant difference test, P = .05). A significant direct correlation was observed between mean flow and mean blood pressure (R = 0.51, P < .02). CONCLUSIONS: Optic nerve blood flow is reduced in glaucoma patients. Glaucoma patients without systemic hypertension have lower optic nerve blood flow than those with hypertension. Our results raise concerns that treatment of systemic hypertension may further decrease optic nerve blood flow in glaucoma patients.

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

Short-term effects of topical levobunolol on the human retinal circulation.

PURPOSE: The effect of topical levobunolol HCl 0.5% on the retinal circulation was studied on 15 normal volunteers aged 21-54 years (32 +/- 10 years). METHODS: In a double-masked, randomised design, one eye of each subject received a drop of levobunolol HCl 0.5% (LEV) and the fellow eye received a drop of artificial tears (TEAR). Leucocyte velocity (VBFS) and density in the retinal macular microcirculation were measured by the blue-field simulation technique. Venous diameter (D), maximum erythrocyte velocity (Vmax) and volumetric blood flow rate (Q) were measured in a major temporal vein by laser Doppler velocimetry and monochromatic fundus photography. RESULTS: The following average changes from baseline were observed 2 hours after treatment: heart rate, -4.6 +/- 8.3% (p = 0.04); intraocular pressure, -31.7 +/- 10.6% (p = 0.0001); and perfusion pressure, 15.4 +/- 14.4% (p = 0.02) in LEV eyes; no statistically significant changes in IOP and perfusion pressure were seen in TEAR eyes. When each eye was compared with its own baseline, there were no significant changes in VBFS, density, D, Vmax and Q in LEV eyes. In TEAR eyes, there were no significant changes in VBFS, density, Vmax and Q, but a significant change in D (-1.8 +/- 2.6%; p = 0.02) was observed. A significant average percentage increase in Q of 10.9 +/- 19.2% (paired t-test between the change after LEV and the change after TEAR, p = 0.044) was seen in LEV eyes when compared with TEAR eyes. Twelve of the 15 subjects demonstrated a relative increase in Q in the LEV eyes in comparison with the TEAR eyes, while 3 subjects showed the opposite. CONCLUSION: A significant difference in the effect of levobunolol between the two eyes was detected, even though there was no statistically significant effect when each eye was compared with its baseline.

Administration, Topical↗
PubMed1997

Effect of one week of levobunolol HCl 0.5% on the human retinal circulation.

PURPOSE: To determine the effect of one week of topical treatment with levobunolol HCl 0.5% on the retinal circulation of normal subjects. METHODS: Fifteen healthy volunteers with no history of ocular disease were included in this study. In a double-masked, randomized, cross-over design, one eye of each subject was treated, for one week, with one drop of either levobunolol or placebo, administered twice daily. Following a washout period of at least three weeks, the same eye received the alternate treatment for one week. Before the beginning of therapy and then two hours after the last drop, vessel diameter (D), maximum erythrocyte velocity (Vmax), and volumetric blood flow rate (Q) were determined in one major retinal vein of the treated eye, using bidirectional laser Doppler velocimetry and monochromatic fundus photography. Statistical analysis was performed using two-tailed, paired Student's t-test, linear regression, and correlation analysis. RESULTS: The average percentage change from baseline in intraocular pressure was statistically significant following levobunolol (-15% +/- 13% (+/-1 SD), P < .001), but not following placebo (-3% +/- 11%, P > .05). No significant changes in average D, Vmax, or Q were observed after levobunolol treatment (-1% +/- 4%, 5% +/- 11%, 4% +/- 15%, respectively) or placebo treatment (-1% +/- 4%, -2% +/- 9%, -5% +/- 10%, respectively). The average difference between the changes in Q from baseline after levobunolol and placebo treatments (9% +/- 17%) achieved a significance level of P = 0.06. Furthermore, following levobunolol treatment, Q was 7% +/- 14% higher than following placebo treatment (P = 0.05). CONCLUSIONS: A comparison of the effects of placebo and levobunolol treatments suggests that levobunolol has a variable effect on the retinal circulation with a tendency to show an overall slight increase in flow.

Adrenergic beta-Antagonists↗
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 hemodynamics in retinitis pigmentosa.

PURPOSE: To investigate the retinal hemodynamic changes occurring in patients with retinitis pigmentosa (RP). METHODS: Bidirectional laser Doppler velocimetry and monochromatic fundus photography were used to determine retinal venous diameter (D), maximum erythrocyte velocity (Vmax), and volumetric blood flow (Q) in the major retinal veins of eight patients with RP and eight age-matched normal controls. The retinal vascular regulatory responses to hyperoxia, defined as the percent decreases in D (RD), Vmax (RVmax), and Q (RQ) at four to six minutes of breathing 100% oxygen, were determined in eight normal subjects and five RP patients. RESULTS: Average D, Vmax, and Q +/- S.D. in the largest retinal vein of each subject were 106 +/- 14 microns, 1.01 +/- 0.20 cm/sec, and 3.5 +/- 1.3 microliters/min, respectively, in RP patients, and 166 +/- 12 microns, 1.79 +/- 0.14 cm/sec, and 14.7 +/- 2.6 microliters/min, respectively, in normal subjects. This corresponded to significant decreases from normal of 36% in D, 44% in Vmax, and 76% in Q in RP patients (Wilcoxon's rank sum test, P < .001). Average total retinal volumetric blood flow rate was 8.2 +/- 2.9 microliters/min in RP patients and 37 +/- 4.9 microliters/min in normal subjects, corresponding to a significant decrease from normal of 78% (Wilcoxon's rank sum test, P < .001). In RP patients, the regulatory responses to hyperoxia (RD, RVmax, and RQ) were similar to those observed in normal subjects. RESULTS: Retinal blood flow is significantly decreased in patients with RP, probably as a result of vascular remodeling in response to reduced metabolic demand. The regulatory responses to hyperoxia are similar to those of normal subjects. Measurements of retinal blood flow may help assess the progression of the disease and the effects of treatment.

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

Rebreathing into a bag increases human retinal macular blood velocity.

AIMS: The effect of rebreathing into a bag (RB) on retinal macular blood velocity was evaluated in healthy volunteers. METHODS: Ten normal volunteers, whose ages ranged from 17 to 34 years, performed RB over 135 to 260 seconds (mean (SD) 193 (38) seconds) while retinal macular blood velocity was determined non-invasively using the blue field simulation technique. RESULTS: Leucocyte velocity significantly increased (p < 0.05) at 2 minutes and at the end of RB by 53% (42%) and 92% (65%), respectively (95% confidence interval of the mean (CIM)). All subjects observed an increase in the density of leucocytes. At the end of RB, mean systolic brachial arterial pressure and heart rate were significantly increased by 24% (11%) and 37% (15%) respectively (p < 0.01). At 2 minutes, end tidal oxygen concentration in the exhaled air was 47% (8%) (95% CIM) below and carbon dioxide was 41% (16%) above baseline (p < 0.001). The RB produces a large increase in macular leucocyte velocity, suggesting an increase in blood flow. CONCLUSION: Although RB has some systemic risk due to hypoxia and hypercapnia, RB for a short period of 1 or 2 minutes might be of help in the treatment of retinal arterial obstructive diseases in young patients without cardiovascular disorders if other treatments do not show any beneficial effects.

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↗