Role of NO in Choroidal Blood Flow Regulation during Isometric Exercise in Healthy Humans

Luksch, Alexandra; Polska, Elżbieta; Imhof, A.; Schering, Joanne; Fuchsjäger-Mayrl, Gabriele; Wolzt, Michael; Schmetterer, Leopold

doi:10.1167/iovs.02-0177

Cited by 71 publications

(70 citation statements)

References 31 publications

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“…16 Previous studies have demonstrated a decrease in choroidal blood flow with intravenously administered systemic inhibitors of NOS. 19 , [40][41][42][43][44][45] A decrease in choroidal blood flow might be expected to lead to a reduction in the choroidal pO 2 , as was observed. In the current study, the retinal vascular pO 2 remained relatively constant with NOS inhibition, consistent with previous studies that have reported no change in the retinal blood flow.…”

Section: Discussionmentioning

confidence: 99%

“…The feasibility of the system for determining pO 2 changes separately in the retinal and choroidal vasculatures was established by varying the fraction of inspired oxygen in rats. Furthermore, because inhibition of nitric oxide synthase (NOS) has been shown to be associated with decreased blood flow in the choroid and, to a lesser degree, in the retinal vascular bed, [16][17][18][19][20][21][22][23][24] this model was also used in the current study to establish the feasibility of our system for measuring chorioretinal pO 2 changes.…”

Section: Introductionmentioning

confidence: 99%

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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%

Section: Introductionmentioning

confidence: 99%

A Method for Chorioretinal Oxygen Tension Measurement

Shahidi¹,

Shakoor²,

Blair³

et al. 2006

Current Eye Research

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“…33,138 The mechanisms of autoregulation in the human eye are, however, complex and not fully explored. [139][140][141][142][143][144][145][146][147][148] No strategy is currently available to normalize autoregulation in disease states associated with abnormal blood flow regulation in response to changes in perfusion pressure. In addition, the time course of loss of RGCs and decline in blood flow is not fully established.…”

Section: Other Approachesmentioning

confidence: 99%

Pharmacotherapy of Glaucoma

Schmidl

Schmetterer²,

Garhöfer³

et al. 2015

Journal of Ocular Pharmacology and Therapeutics

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134

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Glaucoma is a group of diseases involving the optic nerve and associated structures, which is characterized by progressive visual field loss and typical changes of the optic nerve head (ONH). The only known treatment of the disease is reduction of intraocular pressure (IOP), which has been shown to reduce glaucoma progression in a variety of large-scale clinical trials. Nowadays, a relatively wide array of topical antiglaucoma drugs is available, including prostaglandin analogues, carbonic anhydrase inhibitors, beta-receptor antagonists, adrenergic agonists, and parasympathomimetics. In clinical routine, this allows for individualized treatment taking risk factors, efficacy, and safety into account. A major challenge is related to adherence to therapy. Sustained release devices may help minimize this problem but are not yet available for clinical routine use. Another hope arises from non-IOP-related treatment concepts. In recent years, much knowledge has been gained regarding the molecular mechanisms that underlie the disease process in glaucoma. This also strengthens the hope that glaucoma therapy beyond IOP lowering will become available. Implementing this concept with clinical trials remains, however, a challenge.

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“…Stable choroidal layer perfusion pressure is associated with vascular resistance controlled by the sympathetic nervous system (20) . Released from the vascular endothelium, endothelin-1 and nitric oxide (NO) also play a role in the adaptation of choroidal vascular resistance (18,21,22) . The choroidal layer has the ability to regulate ocular perfusion pressure (which is 67% above baseline) (21,23) .…”

Section: Discussionmentioning

confidence: 99%

“…Released from the vascular endothelium, endothelin-1 and nitric oxide (NO) also play a role in the adaptation of choroidal vascular resistance (18,21,22) . The choroidal layer has the ability to regulate ocular perfusion pressure (which is 67% above baseline) (21,23) . It has been shown that stable perfusion is produced by ocular vasoconstriction (20) .…”

Section: Discussionmentioning

confidence: 99%

Evaluation of choroidal thickness in patients with obstructive sleep apnea/hypopnea syndrome

Kara¹,

Özçimen²,

Bekçi³

et al. 2014

Arquivos Brasileiros De Oftalmologia

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Obstructive sleep apnea/hypopnea syndrome (OSAHS) is characterized by transient upper airway resistance caused by a recurrent reduction or cessation of airflow, due to partial or complete occlusion of the upper airway during sleep. It is associated with sleep fragmentation, arousals, bradycardia, tachycardia, and inadequate oxygen saturation despite an increased respiratory effort (1) . Major clinical consequences of the disorder include excessive daytime sleepiness, neurocognitive dysfunction, cardiovascular diseases (hypertension, ABSTRACTPurpose: To compare the subfoveal choroidal thickness (SFCT) of patients with different severities of obstructive sleep apnea/hypopnea syndrome (OSAHS) and normal controls via enhanced depth imaging optical coherence tomography (EDI-OCT). Methods: In this retrospective, case-control study, 49 eyes from 49 patients that had undergone polysomnography were included. SFCT of the horizontal and vertical line scans were manually measured for all eyes based on EDI-OCT images. Two separate analyses were performed according to different apnea/hypopnea index (AHI) groupings. Initial testing was conducted using non-OSAHS, mild OSAHS (5≤AHI<15), moderate OSAHS (15≤AHI<30), and severe OSAHS (AHI≥30) patient groupings, while secondary testing used non-OSAHS, mild OSAHS (5≤AHI<15), and moderate/severe OSAHS (AHI≥15) patient groupings. Results: The mean SFCT was 314.5 µm in the non-OSAHS patients (n=14), 324.5 µm in the mild OSAHS patients (n=15), 269.3 µm in the moderate OSAHS patients (n=11), and 264.3 µm in the severe OSAHS patients (n=9). SFCT between the four groups revealed no significant differences despite a trend towards slight thinning in the severe group (P=0.08). When the moderate and severe groups were merged and compared with the mild OASHS and non-OSAHS groups, SFCT of the moderate/severe group was found to be significantly thinner than that of the mild group (P=0.016). A negative significant correlation was found between SFCT and AHI in OSAHS patients (r=0.368, P=0.033). Conclusions:In patients with moderate/severe OSAHS, EDI-OCT revealed a thinned SFCT. Other accompanying systemic or ocular diseases may induce perfusion and oxygenation deficiency in eyes of OSAHS patients. Further studies are required in order to determine the exact relationships between ocular pathologies and clinical grades of OSAHS. Keywords

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Role of NO in Choroidal Blood Flow Regulation during Isometric Exercise in Healthy Humans

Abstract: These data indicate that NO plays an important role in the regulation of choroidal blood flow during isometric exercise.

Cited by 71 publications

References 31 publications

A Method for Chorioretinal Oxygen Tension Measurement

A Method for Chorioretinal Oxygen Tension Measurement

Pharmacotherapy of Glaucoma

Evaluation of choroidal thickness in patients with obstructive sleep apnea/hypopnea syndrome

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