Studies of the Retinal Circulation in Man

Hickam, John B.; Frayser, Regina

doi:10.1161/01.cir.33.2.302

Cited by 192 publications

(58 citation statements)

References 43 publications

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“…Determination of the vessel diameters is also a sensitive technique for studying the effect of hyperoxia on the retinal vascular bed. Vasoconstriction in the same range as found in the present study has been reported previously (Hickam et al 1959;Deutsch et al 1983;Riva et al 1983;Grunwald et al 1984;Fallon et al 1985;Pakola & Grunwald 1993;Kiss et al 2002). As both flow and volume were reduced, as judged by BFS and vessel diameters, it is perhaps not surprising that we found no change in either MTT IR or AVP.…”

Section: Oxygen Breathingsupporting

confidence: 92%

“…Vasoconstriction has been reported for pure O 2 breathing (Hickam et al 1959;Deutsch et al 1983;Riva et al 1983;Grunwald et al 1984;Fallon et al 1985;Pakola & Grunwald 1993). Pure O 2 breathing reduces blood flow by approximately 60% as estimated from vessel diameter and velocity determined by laser Doppler (Riva et al 1983;Grunwald et al 1984).…”

Section: Introductionmentioning

confidence: 87%

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Effects of oxygen and carbon dioxide on human retinal circulation: an investigation using blue field simulation and scanning laser ophthalmoscopy

Tomić¹,

Bjärnhall²,

Mäepea³

et al. 2005

Acta Ophthalmologica Scandinavica

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ABSTRACT.Purpose: To investigate the quantitative response of retinal circulation in normal human eyes to oxygen and carbon dioxide provocation and to gain more information about retinal mean transit time (MTT). Methods: Healthy subjects were studied while breathing: room air (O 2 baseline); pure O 2 ; room air (CO 2 baseline), and CO 2 in room air. The CO 2 level was brought to 30% above individual baseline level. During each gas exposure, blue field simulation was used to estimate the velocity of macular leucocytes and fluorescein angiography was used to determine MTT, arteriovenous passage time (AVP) and vessel diameters. Results: Breathing pure O 2 caused a reduction in macular leucocyte velocity of about 13%, a non-significant change in MTT and AVP from baseline, and a 10% reduction in the diameter of temporal retinal arteries and veins. Breathing CO 2 caused an increase in macular leucocyte velocity of 21%, a non-significant change in MTT and AVP, and no change in retinal vascular diameters. Conclusion: Both O 2 and CO 2 had the expected effects on retinal blood flow, as judged by leucocyte velocity in the macular capillaries, but little effect on retinal MTT, indicating concomitant changes in flow and retinal vascular volume. Measuring the diameter of retinal vessels before and during pure O 2 breathing is a simple and effective way of determining the reactivity of retinal vessels.

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Section: Oxygen Breathingsupporting

confidence: 92%

Section: Introductionmentioning

confidence: 87%

Effects of oxygen and carbon dioxide on human retinal circulation: an investigation using blue field simulation and scanning laser ophthalmoscopy

Tomić¹,

Bjärnhall²,

Mäepea³

et al. 2005

Acta Ophthalmologica Scandinavica

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“…However, it is believed that the retinal venous blood pressure, which remains above the intraocular pressure, is less affected by changes of body position. 28 We therefore considered the changes in effective MABP to represent alterations of the retinal perfusion pressure.…”

Section: Discussionmentioning

confidence: 99%

“…22,28 These data suggest that the reactivity of the cerebral arteries can be estimated well from the reactivity of the retinal arteries.…”

mentioning

confidence: 88%

Retinal vascular autoregulation in normal subjects.

Tachibana¹,

Gotoh²,

Ishikawa³

1982

Stroke

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SUMMARY The retinal arterial diameter and its response to changes in perfusion pressure were measured by means of a fundus camera in 65 normal subjects. A reduction of effective MABP was induced by a postural change from a recumbent to an erect position. A small but significant increase in retinal arterial diameter was observed by reduction of the perfusion pressure in all subjects.The reduction of retinal arterial reactivity in response to blood pressure changes (-% change in diameter/A effective MABP) was significantly correlated with advancing age (p < 0.01). No significant correlations were observed between the retinal arterial reactivity, magnitude of the retinal arterial diameter (range: 60-140 n), and systemic blood pressure (range of MABP: 75-110 mmHg).These results indicate that the retinal artery has an autoregulatory mechanism which is influenced by aging. Stroke, Vol 13, No 2, 1982 CEREBROVASCULAR AUTOREGULATION is defined as constancy of blood flow despite changes in perfusion pressure within the range of 50-160 mmHg. 1,2 The mechanism of autoregulation is mediated by changes in arterial calibre; the vessels dilate as the pressure falls and constrict as the pressure rises. Although cerebrovascular autoregulation is known to be altered in various diseases 8, *• e and conditions, 3, 8 " 8 little is known about the effects of aging on the autoregulation in normal subjects. This lack of basic data is probably related in part to the traumatic and invasive nature of the techniques for estimating autoregulation.The retinal artery, a branch of the ophthalmic artery deriving from the internal carotid artery, is considered to represent part of the cerebral vessels and is the only vessel seen directly under physiological conditions. Several workers 8,1B have reported that the human retinal circulation responds actively to changes in perfusion pressure, thus demonstrating the presence of an autoregulatory mechanism in the retina. Furthermore, the retinal vessels react to changes in oxygen 16 "18 and carbon dioxide tension 18,18~21 as noted in the cerebral vessels. 22,28 These data suggest that the reactivity of the cerebral arteries can be estimated well from the reactivity of the retinal arteries.The purpose of the present study was to investigate the retinal vascular autoregulation in normal subjects of various ages and to assess the influence of aging on the cerebrovascular autoregulation.Department of Neurology, School of Medicine, Keio University, 35 Shinanomachi, Shinjuku-ku, Tokyo 160, Japan.Mailing Address: Hisao Tachibana, M.D., Department of Neurology, School of Medicine, Keio University, 35 Shinanomachi, Shinjuku-ku, Tokyo 160, Japan. Materials and MethodsSixty-five normal subjects (40 males, 25 females) with ages ranging from 18 to 73 (mean 36 years) were included in the present study. Thirty-seven were volunteers, while the remaining 28 were out-patients of Keio University hospital. All were fully active, independent, and non-hospitalized. The out-patients underwent detailed interviews and g...

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“…In humans, the increased retinal oxygen tension in light should lead to autoregulatory vasoconstriction (14) in the retina and reduced retinal blood flow in vascularized retinas in light as has been observed in the human retina (15,16).…”

Section: Discussionmentioning

confidence: 88%

Retinal Oxygen Tension Is Higher in Light than Dark

Stefánsson

1988

Pediatr Res

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ABSTRACT. The oxygen tension at the inner retinal surface in rabbits was measured with intraocular polarographic electrodes. In the air breathing rabbit, the oxygen tension is 21 f 9 mm Hg (mean f 1 SD, n = 6) in 12 footcandles white light at the cornea. The oxygen tension falls 6 + 2 mm Hg (mean 2 I SD, n = 4, p < 0.02) in darkness.In bright white light (800 foot-candles), the retinal oxygen tension is about 6 mm Hg higher than at 12 foot-candles. The in vivo retinal oxygen consumption was calculated to be 2.4 ml 02/100 g/min in light and 2.6 ml 02/100 g/min in dark. The higher oxygen consumption is probably responsible for the lower oxygen tension of the retina in dark as compared to light. Breathing The physiological effects of light and oxygen on the retina are of considerable general interest and specifically play a role in the pathogenesis of retinopathy of prematurity. Retinopathy of prematurity has long been known to be related to oxygen breathing (I). Recently, Glass et al. (2) reported that bright lights also contribute to the development of retinopathy of prematurity. This report shows that light elevates the retinal oxygen tension in rabbits. Therefore, illumination may not be an independent risk factor for the development of retinopathy of prematurity, but rather acts through raising the retinal oxygen tension. The report also shows that preretinal oxygen levels rise to levels above the hemoglobin saturation level when the rabbits breathe 100% oxygen. The extraordinarily high oxygen tension of the retina in hyperoxia may help explain the sensitivity of the immature retina to oxygen breathing. Also a method to calculate the retinal oxygen consumption in vivo is shown, and the oxygen consumption calculated in light and dark. MATERIALS AND METHODSSix New Zealand Red rabbits were anesthetized with ketamine hydrochloride (20-30 mg/kg intramuscularly) and anesthesia was maintained with alphachloralose (80 mg/kg intravenously). The pupils were dilated with 2.5% phenylephrine and 1 % tropicamide on the cornea. The rabbits were intubated and mechanically ventilated. A femoral artery was cannulated for continuous arterial blood pressure measurements and arterial blood oxygen and carbon dioxide tension, pH (blood gas analyzer, Instrumentation Laboratory Inc., Lexington, MA, model 7 13), and hematocrit determinations (Table 1). The electrocardiogram and rectal temperature were continuously monitored and body temperature maintained close to 38" C with a heating pad. The animal was placed in a stereotactic head holder. A lateral canthotomy and a conjunctival peritomy were performed. Holding ties were placed under two recti muscles. The sclera was punctured with a cannula in the area of the pars plana of the ciliary body and the polarographic oxygen electrode (Diamond Electrotech Inc., MI, model 760) placed in the vitreous gel approximately 0.1 mm in front of the avascular retina as described previously (3, 4). The preretinal oxygen tension was measured continuously while the light levels varied between darkness ...

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Studies of the Retinal Circulation in Man

Cited by 192 publications

References 43 publications

Effects of oxygen and carbon dioxide on human retinal circulation: an investigation using blue field simulation and scanning laser ophthalmoscopy

Effects of oxygen and carbon dioxide on human retinal circulation: an investigation using blue field simulation and scanning laser ophthalmoscopy

Retinal vascular autoregulation in normal subjects.

Retinal Oxygen Tension Is Higher in Light than Dark

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