Retinal Blood Flow during Hyperoxia in Humans Revisited: Concerted Results Using Different Measurement Techniques

Kiss, Barbara; Polska, Elżbieta; Dorner, Guido T.; Polak, Kaija; Findl, Oliver; Mayrl, Gabriele Fuchsjäger; Eichler, Hans‐Georg; Wolzt, Michael; Schmetterer, Leopold

doi:10.1006/mvre.2002.2402

Cited by 70 publications

(73 citation statements)

References 19 publications

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“…It is known that both retinal veins and arteries constrict in response to hyperoxic challenge. [33][34][35] Consequently, assuming constant oxygen consumption, the lower resultant blood flow through the retinal vasculature will presumably result in a higher fractional extraction of oxygen and hence an increase in the A-V difference. At pO 2 over about 100 mmHg, hemoglobin is saturated with oxygen.…”

Section: Discussionmentioning

confidence: 99%

A Method for Chorioretinal Oxygen Tension Measurement

Shahidi¹,

Shakoor²,

Blair³

et al. 2006

Current Eye Research

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Purpose-To report an optical imaging system that was developed to measure oxygen tension (pO 2 ) in the chorioretinal vasculatures. The feasibility of the system for the measurement of changes in pO 2 separately in the retinal and choroidal vasculatures was established in rat eyes by varying the fraction of inspired oxygen and inhibiting nitric oxide activity.Methods-Our optical section phosphorescence imaging system was modified to provide quantitative measurements of pO 2 separately in the retinal and choroidal vasculatures. A narrow laser line was projected at an angle on the retina after intravenous injection of an oxygen-sensitive probe (Pd-porphyrin), and phosphorescence emission was imaged. A frequency-domain approach allowed measurements of the phosphorescence lifetime by varying the phase relationship between the modulated excitation laser light and sensitivity of the imaging camera. Chorioretinal pO 2 was measured while varying the fraction of inspired oxygen and during intravenous infusion of N ω -nitro-L-arginine (N ω -NLA), a nonselective nitric oxide synthase inhibitor.Results-The systemic arterial pO 2 varied according to the fraction of inspired oxygen. The pO 2 in the retinal and choroidal vasculatures increased as the fraction of inspired oxygen was increased. Compared with base-line, choroidal pO 2 decreased during infusion of N ω -NLA, whereas the pO 2 in the retinal vasculatures remained relatively unchanged. The choroidal pO 2 decreased markedly with each incremental increase in N ω -NLA infusion rate, in the range 1-6 mg/min, and there was no additional change in the choroidal pO 2 at N ω -NLA infusion rates above 6 mg/min.Conclusions-An optical method combining pO 2 phosphorescence imaging with chorioretinal optical sectioning was established that can potentially be applied for better understanding of retinal and choroidal oxygen dynamics in physiologic and pathologic states.

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Section: Discussionmentioning

confidence: 99%

A Method for Chorioretinal Oxygen Tension Measurement

Shahidi¹,

Shakoor²,

Blair³

et al. 2006

Current Eye Research

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“…Alternatively, others have measured retinal vessel diameter and separately employed a bidirectional laser Doppler system to measure centerline retinal blood velocity to calculate flow (22,31,34,(37)(38)(39)42 In general, previous studies using 100% O 2 to assess retinal vascular reactivity have tended to find a greater magnitude of vasoconstriction, which we attribute to a compounded effect of elevated arterial O 2 and reduced CO 2 (22,37,38,42). Most of these studies have measured vascular reactivity in venules, possibly because the derived velocity profile was nonpulsatile.…”

Section: Discussionmentioning

confidence: 99%

“…In particular, retinal blood flow is strongly dependent on the partial pressure of oxygen (PO 2 ; Refs. 14,25,31,42,48).The retinal vasculature can be noninvasively visualized and, consequently, its hemodynamic parameters quantified. Impairment of vascular reactivity has been demonstrated in the pathogenesis of various ocular diseases including diabetic retinopathy (13,20,25,32).…”

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confidence: 99%

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Retinal arteriolar diameter, blood velocity, and blood flow response to an isocapnic hyperoxic provocation

Gilmore¹,

Hudson²,

Preiss³

et al. 2005

American Journal of Physiology-Heart and Circulatory Physiology

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Fisher. Retinal arteriolar diameter, blood velocity, and blood flow response to an isocapnic hyperoxic provocation. Am J Physiol Heart Circ Physiol 288: H2912-H2917, 2005. First published February 11, 2005 doi:10.1152/ajpheart.01037.2004.-The aim of this study was to simultaneously quantify the magnitude and response characteristics of retinal arteriolar diameter and blood velocity induced by an isocapnic hyperoxic provocation in a group of clinically normal subjects. The sample comprised 10 subjects (mean age, 25 yr; range, 21-40 yr). Subjects initially breathed air for 5-10 min, then breathed O 2 for 20 min, and then air for a final 10-min period via a sequential rebreathing circuit (Hi-Ox; Viasys) to maintain isocapnia. Retinal arteriolar diameter and blood velocity measurements were simultaneously acquired with a Canon laser blood flowmeter (CLBF-100). The response magnitude, time, and lag of diameter and velocity were calculated. In response to hyperoxic provocation, retinal diameter was reduced from control values of 111.6 (SD 13.1) to 99.8 (SD 10.6; P Ͻ 0.001) m and recovered after withdrawal of hyperoxia. Retinal blood velocity and flow concomitantly declined from control values of 32.2 (SD 6.4) mm/s and 9.4 (SD 2.5) l/min to 20.7 (SD 3.4) mm/s and 5.1 (SD 1.3) l/min, respectively (P Ͻ 0.001 for both velocity and flow), and recovered after withdrawal of hyperoxia. The response times and response lags were not significantly different for each parameter between effect and recovery or between diameter and velocity. We conclude that arteriolar retinal vascular reactivity to hyperoxic provocation is rapid with a maximal vasoconstrictive effect occurring within a maximum of 4 min. Although there was a trend for diameter to respond before velocity to the isocapnic hyperoxic provocation, the response characteristics were not significantly different between diameter and velocity. vascular reactivity; laser Doppler velocimetry; isocapnic hyperoxia THE BLOOD SUPPLY TO THE INNER retina is derived from the central retinal artery, whereas the choriocapillaris supplies the outer retina and photoreceptors. The retinal tissue is one of the most metabolically active in the body and, correspondingly, an uninterrupted nutrient supply is essential (50). The inner retinal blood vessels (i.e., past the lamina cribrosa) are thought to be unique due to the absence of an autonomic nerve supply to regulate vascular tone (53). Blood supply to the inner retina is regulated via local feedback signals that alter retinal perfusion in response to changes in systemic blood pressure or the concentration of certain metabolites (11,18). In particular, retinal blood flow is strongly dependent on the partial pressure of oxygen (PO 2 ; Refs. 14,25,31,42,48).The retinal vasculature can be noninvasively visualized and, consequently, its hemodynamic parameters quantified. Impairment of vascular reactivity has been demonstrated in the pathogenesis of various ocular diseases including diabetic retinopathy (13,20,25,32). Administration of O 2 has p...

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“…Inhalation of 100% O 2 is associated with retinal arteriolar vasoconstriction with minimal effect on systemic hemodynamics, and O 2 administration has been previously used as a test of retinal vascular reactivity by a number of investigators (19,35,48). We found that inhalation of 100% O 2 was accompanied by vasoconstriction of the retinal arterioles and that the magnitude of the change was greater in control subjects compared with patients with type 1 diabetes.…”

Section: Discussionmentioning

confidence: 72%