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Background/aims: In a previously described model of isolated rabbit eye, we detected myogenic intrinsic vascular tone of unknown origin in the ophthalmic artery. In order to better understand the origin of these low frequency oscillations, we analyzed their spectral characteristics using fast Fourier., Methods: Hybrid New Zealand rabbits of either sex (n = 24) were used; they were divided into 2 groups according to age. The spectral characteristics of the myogenic behaviour of the rabbit external ophthalmic artery were analyzed using the fast Fourier algorithm., Results: The frequency of the oscillations of the myogenic activity seen in the rabbit external ophthalmic artery varied between 0.033 and 0.066 Hz (mean 0.045 ± 0.012 Hz), all in the region of very low frequency (VLF) oscillations (VLF <0.07 Hz for the rabbit). The frequency of spontaneous oscillations was higher in younger animals., Conclusion: Fast Fourier analysis proved to be an adequate mathematical tool to analyze the myogenic tone oscillations, which were all in the range of VLF in the model we used. These results indicate that myogenic vascular function of ocular blood flow is composed of VLF oscillations, and they provide a new explanation for the origin of VLF in arterial spectra. They also suggest that the ocular local myogenic vascular function observed is more efficient in younger animals., (Copyright © 2013 S. Karger AG, Basel.)

Background: Resistive index (RI) is an indirect measurement of blood flow resistance that can be used to evaluate vascular damage., Aims: The purpose of this study is to evaluate the association between RI values of orbital and intrarenal arteries by means of Doppler ultrasonography (US)., Methods: We evaluated 103 diabetic patients. As a control group, 30 subjects were examined. The patients were divided into two groups. Group 1 consisted of patients with urinary albumin excretion (UAE) <300 mg/day and estimated glomerular filtration rate (eGFR) levels >90 ml/min (n = 50); Group 2 had a UAE >300 mg/day and/or eGFR levels between 89 and 60 ml/min (n = 53). The association between RI values obtained with Doppler US of the ophthalmic artery, central retinal artery, posterior ciliary artery and intrarenal arteries were calculated., Results: Both orbital and intrarenal arterial RI values in Group 1 and Group 2 were higher than the control group (p = 0.001); furthermore, values were higher in Group 2 than in Group 1 (p = 0.0004/0.029/0.036, p = 0.016, respectively). A positive correlation was found between orbital and intrarenal arterial RI values in Group 2 (r = 0.475, 0.285, 0.363, p < 0.01, respectively)., Conclusion: Both orbital and renal arterial RI values were shown to be higher than the control group. Further, a trend towards higher RI values was observed with renal disease. RI may be useful as one of the markers for early diagnosis and follow-up of diabetic nephropathy and retinopathy., (Copyright © 2012 S. Karger AG, Basel.)

Background/aims: Although nitric oxide (NO) has been shown to be essential for maintaining the basal blood flow in the retina and optic nerve head, its exact role in vasomotion is still controversial. This study investigated L-arginine (L-Arg) and N-nitro-L-arginine methylester (L-NAME) effects on vascular reactivity in a model of isolated rabbit eye., Methods: Rabbit external ophthalmic arteries (n = 12) in a head-mounted preparation were cannulated and perfused with warmed Tyrode solution. The effect of intraluminal pressure as a measure of total vascular resistance was assessed. Response curves to intra-arterial injections of 3 growing concentrations of L-Arg (n = 6) and L-NAME (n = 6) were obtained., Results: Without any drug administration, spontaneous oscillations were observed in all the models. L-Arg (NO precursor) induced vasodilation and decreased both frequency and amplitude of the periodic oscillations. L-NAME (NO synthase inhibitor) produced a strong vasoconstrictor tone and stimulated vasomotion, causing a faster rate of pulsatility., Conclusion: L-Arg and L-NAME acted as modulators of ocular vascular tone. L-Arg elicited vasodilation and decreased vasomotion while L-NAME produced a strong vasoconstrictor tone and caused a faster rate of pulsatility. These findings justify the need to investigate NO precursors and antagonists as possible alternative therapeutics in vascular eye diseases., (Copyright 2009 S. Karger AG, Basel.)

Purpose: To evaluate the physiological effects of hypercapnia on the retrobulbar vasculature in ocular hypertension (OH) and open-angle glaucoma (OAG)., Methods: Peak systolic velocity (PSV), end-diastolic velocity (EDV) and resistive index (RI) of the ophthalmic (OA) and central retinal arteries (CRA) were evaluated in 12 eyes with OH and 8 eyes with OAG using color Doppler imaging. Measurements were taken before and during hypercapnia., Results: Patients with OAG were found to have increased EDV (p < 0.035) of the CRA, and decreased PSV (p < 0.097) and EDV (p < 0.098) of the OA, during hypercapnia. Patients with OH had increased PSV (p < 0.062) and EDV (p < 0.072) of the CRA during hypercapnia. Patients with OH also demonstrated a greater percent change in the calculated RI (p < 0.065) of the CRA in response to hypercapnia when compared to OAG. The mean RI of the CRA decreased during hypercapnia., Discussion: Patients with OH were found to have a normal vasodilatory response within the retrobulbar vasculature during hypercapnia resulting in increased volumetric blood flow to the retina while patients with OAG did not, suggesting there is vasospasm at or downstream from the CRA resulting in decreased volumetric blood flow to the retina.

Objective: To evaluate the effects of menopause and hormone replacement therapy (HRT) on the quality and amount of tear, intraocular pressure (IOP) and retrobulbar blood flow velocities., Patients and Methods: Twenty women aged between 40 and 50 years, free of ocular and systemic diseases and planning to receive HRT were recruited as the study group. Twenty-four healthy, age-matched but still menstruating women were enrolled as controls. On the first day of study basal and reflex Schirmer test, tear break-up time and IOP measurements (at 08.00, 12.00 and 16.00 h) were performed for all groups. On the second day of the study, the peak systolic velocity (PSV), end diastolic velocity (EDV) and resistivity index (RI) of the ophthalmic (OA), central retinal (CRA), nasal (NSPCA) and temporal short posterior ciliary (TSPCA) arteries were determined by color Doppler imaging. The menopausal group received HRT for 2 months, when all measurements were repeated for the 15 women who had received HRT on a daily basis., Results: The quality and amount of tear decreased (p < 0.01), IOP (p < 0.01) and RI of the CRA, TPCA and NPCA (p < 0.05) increased in postmenopausal women compared with the control group. After 2 months of HRT, the quality and amount of tear had increased (p < 0.001) and the IOP had decreased (p < 0.001). The PSV of the CRA and TSPCA had decreased (p < 0.05), as had the RI in the CRA (p < 0.001), NSPCA and TSPCA (p < 0.05)., Conclusion: We conclude that age-induced changes on quality and amount of tear, IOP and retrobulbar blood flow are intensified by the menopause and that it may be possible to decrease the menopausal effects on these parameters by HRT., (Copyright 2004 S. Karger AG, Basel)

Purpose: To assess the blood flow changes in eyes with central retinal vein occlusion (CRVO) and compare these values with values of fellow eyes and eyes of normal subjects., Methods: 25 eyes of 25 consecutive newly diagnosed patients with CRVO comprised the study group. Their fellow eyes and those of 25 healthy subjects were the control group. All patients underwent a complete ophthalmological examination. Eyes with CRVO were classified into two groups as non-ischaemic and ischaemic by fundus fluorescein angiography. Colour Doppler imaging was performed with a Toshiba Sonolayer SSH-140A and 7.5-MHz linear array probe. Maximum systolic velocity (V(max)), end-diastolic velocity (V(min)) and resistive index (R(i)) values were noted for each of the central retinal artery (CRA), central retinal vein (CRV) and ophthalmic artery (OA). These parameters were compared with those of the fellow eyes and both eyes of the control group., Results: Mean ages were 63.55 and 61.45 years in the CRVO and control groups, respectively. Age and sex distributions were statistically identical in both groups. When we compared the eyes with CRVO to the control group, no statistically significant difference existed between the two groups with regard to the V(min) and R(i )values of the CRA and CRV. However, V(max ) values of the CRA and CRV were significantly lower in CRVO eyes when compared to the control group. The CRVO group and control group had similar V(max), V(min ) and R(i) values for the OA. Only the V(max) was significantly lower in the CRV in eyes with CRVO when compared to the unaffected fellow eyes. No statistically significant difference could be detected between any of the parameters of CRA, CRV and OA of the ischaemic and non-ischaemic CRVO groups., Conclusions: More data on broader series need to be obtained in order to decide on the practical use of colour Doppler imaging in the differentiation of ischaemic eyes from non-ischaemic eyes in CRVO., (Copyright 2002 S. Karger AG, Basel)

The authors considered a group of patients with newly diagnosed primary open-angle glaucoma studying the effects of a 4-week treatment with timolol or dorzolamide on retrobulbar vessels. Ocular hemodynamics were assessed by means of color Doppler imaging of the ophthalmic artery, the temporal short posterior ciliary arteries (SPCAs) and the central retinal artery. For each vessel, systolic and diastolic blood flow velocities were measured, and the resistivity index (RI) was calculated. The only significant result was a reduction of temporal SPCA RI after dorzolamide treatment in comparison with baseline (p = 0.011). In the same group, dorzolamide treatment had a slight and nonsignificant increase in temporal SPCA diastolic velocity. The resistance decrease observed after dorzolamide treatment in the ciliary circulation may be due to the decrease in intraocular pressure or a possible direct vasodilating effect of the drug., (Copyright 2002 S. Karger AG, Basel)

The authors investigated the effect of ketanserin 0.5% eye drops on intraocular pressure and orbital blood flow in some healthy volunteers. Ketanserin is a selective antagonist of serotonin S(2) receptors; moreover, it produces an alpha(1)-blocking effect. It causes a systemic reduction of blood pressure and capillary vasodilatation. Three hours after topical administration of ketanserin 0.5%, the intraocular pressure was decreased by about 14% from the baseline. At the same time, we observed by color Doppler imaging that the mean percent increase in the peak systolic velocity in the ophthalmic artery (OA) was 5.18% (p < 0.161) and 23.18% (p < 0.001) in the posterior ciliary arteries (PCAs). The mean resistance index of the OA was in contrast reduced by 1.16% (p < 0.669) and by 32.14% (p < 0.003) in the PCAs. These data show that ketanserin 0.5% eye drops may be useful not only to decrease intraocular pressure but also to improve blood flow in the PCAs that supply the optic nerve head.

Purpose: Because the protean biological effects of ethanol include acute alterations in both cortical function and circulatory control, we investigated the effect of acute alcohol consumption on retrobulbar hemodynamics and contrast sensitivity in healthy human volunteers., Subjects and Methods: Twelve young adults received orange juice with and without ethanol in a double-masked fashion. The ethanol dose was sufficient to raise blood alcohol to 0.07 +/- 0.003 g/dl. Retrobulbar hemodynamics were assessed at baseline and twice at elevated blood alcohol by color Doppler imaging., Results: Acute elevation of blood alcohol lowered intraocular pressure from 13.0 +/- 0.7 to 10.7 +/- 0.7 mm Hg (p < 0.05). In contrast, elevated blood alcohol left peak systolic velocity, end-diastolic velocity and the resistance index constant in three retrobulbar arteries (ophthalmic, central retinal and posterior ciliary). For example, in the central retinal artery, peak systolic velocity, end-diastolic velocity and the resistance index averaged 11.0 +/- 1.3 cm/s, 2.8 +/- 0.4 cm/s and 0.75 +/- 0.03 before ethanol, as compared with 10.5 +/- 1.0 cm/s, 2.9 +/- 0.3 cm/s and 0.72 +/- 0.03 after ethanol (all p = NS). Alcohol ingestion also failed to alter either visual acuity or contrast sensitivity, as assessed under both photopic and mesopic conditions., Conclusions: Although ethanol has widespread cognitive and cardiovascular effects, at blood levels near legal definitions of intoxication we found it ineffective in altering either retrobulbar hemodynamics or contrast sensitivity.

The authors evaluated, by means of color Doppler imaging, the blood flow of the ophthalmic artery, ciliary arteries and central retinal artery in normal and glaucomatous subjects. In normals they found that flow velocities of all considered vessels progressively decline while resistivity indices increase with advancing age. In glaucomatous subjects there was a statistically significant reduction of the mean systolic peak flow velocity of the ophthalmic artery in comparison with normals. Glaucomatous eyes with uncontrolled IOP and with visual-field worsening showed a statistically significant decrease in the end-diastolic flow velocities and an increase in the resistivity index values in ciliary arteries.