Retinal Arteriolar Dilation to Flicker Light Is Reduced on Short-Term Retesting

Noonan, Jonathan; Nguyen, Thanh T.; Best, W; Wang, Jie Jin; Lamoureux, Ecosse L.

doi:10.1167/iovs.13-12525

Cited by 13 publications

(12 citation statements)

References 25 publications

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“…In contrast, large vessels are disproportionately represented in the standard vessel density (%) measurements. Numerous studies have shown an increase in large vessel flow velocity and vessel diameter during flicker stimulation 16–26. In our study, the increase in vessel density and decrease in VLD in the SCP during ambient light and flicker stimulation suggest active dilation of the larger vessels and redistribution of blood from the smaller capillaries to either the larger SCP vessels or toward the deeper layers via anastomoses, which are vertically oriented (parallel to the OCT beam) and may therefore be difficult to detect with OCTA 28…”

Section: Discussionmentioning

confidence: 59%

“…Flicker stimulation studies have produced more consistent results, perhaps in part because flicker leads to neural activation in the inner retina, where most previous hemodynamic studies have focused. Flicker-induced arterial and venular vasodilation and increased blood flow velocity have been reported in humans and rodents 16–26. The techniques used to study the vascular response to dark adaptation and flicker stimulation in humans have largely been limited to large vessels.…”

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confidence: 99%

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Hemodynamic Response of the Three Macular Capillary Plexuses in Dark Adaptation and Flicker Stimulation Using Optical Coherence Tomography Angiography

Nesper

Lee

Fayed

et al. 2019

Invest. Ophthalmol. Vis. Sci.

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Citation: Nesper PL, Lee HE, Fayed AE, Schwartz GW, Yu F, Fawzi AA. Hemodynamic response of the three macular capillary plexuses in dark adaptation and flicker stimulation using optical coherence tomography angiography. Invest Ophthalmol Vis Sci. 2019;60:694-703. https://doi.org/ 10.1167/iovs.18-25478 PURPOSE. To assess retinal microvascular reactivity during dark adaptation and the transition to ambient light and after flicker stimulation using optical coherence tomography angiography (OCTA). METHODS.Fifteen eyes of 15 healthy participants were dark adapted for 45 minutes followed by OCTA imaging in the dark-adapted state. After 5 minutes of normal lighting, subjects underwent OCTA imaging. Participants were then subjected to a flashing light-emitting diode (LED) light and repeat OCTA. Parafoveal vessel density and adjusted flow index (AFI) were calculated for superficial (SCP), middle (MCP), and deep capillary plexuses (DCP), and then compared between conditions after adjusting for age, refractive error, and scan quality. SCP vessel length density (VLD) was also evaluated. Between-condition capillary images were aligned and subtracted to identify differences. We then analyzed images from 10 healthy subjects during the transition from dark adaptation to ambient light.RESULTS. SCP vessel density was significantly higher while SCP VLD was significantly lower during ambient light and flicker compared to dark adaptation. There was a significant positive mean value for DCP ''flicker minus dark or light,'' suggesting more visible vessels during flicker due to changes in flow, dilation, or vessel recruitment. We found a significant, transient increase in SCP and decrease in both MCP and DCP vessel density during the transition from dark to light.CONCLUSIONS. We show evidence suggesting constriction of deeper vessels and dilation of large SCP vessels during the transition from dark to light. This contrasts to redistribution of blood flow to deeper layers during dark adaptation and flicker stimulation.

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Section: Discussionmentioning

confidence: 59%

mentioning

confidence: 99%

Hemodynamic Response of the Three Macular Capillary Plexuses in Dark Adaptation and Flicker Stimulation Using Optical Coherence Tomography Angiography

Nesper

Lee

Fayed

et al. 2019

Invest. Ophthalmol. Vis. Sci.

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“…Limitations of this study were a small sample of nine subjects and a low contrast stimulus with a minor chromatic component. Another study of healthy subjects that used a high contrast, fixed green wavelength 12.5 Hz flicker found arteriole and venule dilations after 20 s of 3.2% and 4.3%, respectively . Proximal venule dilations are typically larger but less reproducible than proximal arteriole dilations during flicker stimulation.…”

Section: Flicker‐evoked Retinal Haemodynamic Changesmentioning

confidence: 99%

“…Another study of healthy subjects that used a high contrast, fixed green wavelength 12.5 Hz flicker found arteriole and venule dilations after 20 s of 3.2% and 4.3%, respectively. 38 Proximal venule dilations are typically larger but less reproducible than proximal arteriole dilations during flicker stimulation. This could be due to different contributions of vessel dilations and increased velocities to hyperaemia in the arterial and venous circulations.…”

Section: Flicker-evoked Retinal Haemodynamic Changesmentioning

confidence: 99%

Neuronal activity‐dependent regulation of retinal blood flow

Noonan

Lamoureux

Sarossy

2015

Clinical Exper Ophthalmology

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Blood flow in the retina is intrinsically regulated to meet the metabolic demands of its constituent cells. Flickering light or stationary contrast reversals induce an increase in blood flow within seconds of the stimulus onset. This phenomenon is thought to compensate for an increase in ganglion cell activity and energy consumption. Ganglion cell activity is in turn dependent on signals from photoreceptors, bipolar cells, horizontal cells and amacrine cells. The physiological properties of these neurons determine how each type is affected by a particular light characteristic. Neuronal activity then triggers the release of signalling molecules that dilate local blood vessels and increase blood flow. Nitric oxide has been implicated as an important mediator, but metabolites of arachidonic acid may also be involved. Detailed elucidation of these mechanisms, together with advances in imaging technology, may facilitate the use of neurovascular tests to improve the detection of retinal damage in pathological conditions.

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“…(Palkovits et al, 2015) Although increased MO 2 is expected to reduce the intraretinal tissue oxygen tension (tPO 2 ), there are, in fact, two compensatory responses that counteract this reduction of tPO 2 . First, neurovascular coupling, which is active in both the inner retina and optic nerve,(Kornfield and Newman, 2014; Kur et al, 2012; Newman, 2013; Riva et al, 2005; Trick and Berkowitz, 2005) leads to vasodilation(Formaz et al, 1997; Kotliar et al, 2004; Mishra et al, 2011; Noonan et al, 2013; Palkovits et al, 2014; Polak et al, 2002) and increased blood velocity,(Michelson et al, 2002; Mishra et al, 2011; Scheiner et al, 1994) both of which augment retinal blood flow,(Garhofer et al, 2004; Kiryu et al, 1995; Shih et al, 2013) and inner retinal oxygen delivery (i.e., the product of retinal blood flow and arterial oxygen concentration). Second, the inner retina can change the rate at which oxygen is removed from the blood, thereby altering the arteriovenous oxygen concentration difference,(Hammer et al, 2011; Shakoor et al, 2006) and the oxygen extraction fraction (OEF).…”

Section: Introductionmentioning

confidence: 99%

Retinal tissue oxygen tension and consumption during light flicker stimulation in rat

Blair

Tan

Felder

et al. 2018

Experimental Eye Research

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Light flicker stimulation has been shown to increase inner retinal oxygen metabolism and supply. The purpose of the study was to test the hypothesis that sustained light flicker stimulation of various durations alters the depth profile metrics of oxygen partial pressure in the retinal tissue (tPO) but not the outer retinal oxygen consumption rate (QO). In 17 rats, tPO depth profiles were derived by phosphorescence lifetime imaging after intravitreal injection of an oxyphor. tPO profile metrics, including mean inner retinal tPO, maximum outer retinal tPO and minimum outer retinal tPO were determined. QO was calculated using a one-dimensional oxygen diffusion model. Data were acquired at baseline (constant light illumination) and during light flicker stimulation at 10 Hz under the same mean illumination levels, and differences between values obtained during flicker and baseline were calculated. None of the tPO profile metrics or QO differences depended on the duration of light flicker stimulation (R ≤ 0.03). No significant change in any of the tPO profile metrics was detected with light flicker compared with constant light (P ≥ 0.08). Light flicker decreased QO from 0.53 ± 0.29 to 0.38 ± 0.30 mL O/(min*100 gm), a reduction of 28% (P = 0.02). The retinal compensatory responses to the physiologic challenge of light flicker stimulation were effective in maintaining the levels of oxygen at or near baseline in the inner retina. Oxygen availability to the inner retina during light flicker may also have been enhanced by the decrease in QO.

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Retinal Arteriolar Dilation to Flicker Light Is Reduced on Short-Term Retesting

Cited by 13 publications

References 25 publications

Hemodynamic Response of the Three Macular Capillary Plexuses in Dark Adaptation and Flicker Stimulation Using Optical Coherence Tomography Angiography

Hemodynamic Response of the Three Macular Capillary Plexuses in Dark Adaptation and Flicker Stimulation Using Optical Coherence Tomography Angiography

Neuronal activity‐dependent regulation of retinal blood flow

Retinal tissue oxygen tension and consumption during light flicker stimulation in rat

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