PubMed Health⌕ Search

Biomedical subjects

L Schmetterer

Publications and source records attributed to L Schmetterer.

At least 19 recordsLinked to original sources
PubMed2004

Diffuse luminance flicker increases blood flow in major retinal arteries and veins.

It has been shown that diffuse luminance flicker increases optic nerve head blood flow. The current study has been performed to quantify changes in retinal blood flow during flicker stimulation. In a group of 11 healthy volunteers, red blood cell velocity and retinal vessel diameters were assessed with bi-directional laser Doppler velocimetry and the Zeiss retinal vessel analyzer before, during and after stimulation with diffuse luminance flicker. Retinal blood flow was calculated for each condition. Flicker stimulation increased retinal blood flow by +59 +/- 20% (p<0.01) in arteries and by +53 +/- 25% (p<0.01) in retinal veins. These results demonstrate that diffuse luminance flicker increases retinal blood flow in the human retina.

Adult↗
PubMed2004

Clonidine added to bupivacaine enhances and prolongs analgesia after brachial plexus block via a local mechanism in healthy volunteers.

BACKGROUND AND OBJECTIVE: The addition of clonidine to local anaesthetics enhances pain relief after peripheral nerve block, but the site of action is unproven. METHODS: Seven healthy volunteers underwent three brachial block procedures using bupivacaine 0.25% 1 mg kg(-1) + epinephrine 1:200,000 (=local analgesic) in a randomized, double-blind cross-over fashion: (a) control treatment: local analgesic with 0.9% sodium chloride solution for the block and an intramuscular injection of saline; (b) intramuscular treatment: local analgesic with 0.9% NaCl for block and an intramuscular injection of clonidine 2 microg kg(-1) and (c) block treatment: local analgesic with clonidine 2 microg kg(-1) for block and an intramuscular injection of saline. RESULTS: The onset and duration of complete blockade (sensory/motor/temperature) was evaluated in the four nerve regions of the hand and forearm. Additionally, sedation score, blood pressure, heart rate and plasma clonidine concentrations were determined. The median duration of complete sensory blockade was 270 min (range 0-600) for block treatment compared to 0 min (range 0-480) for intramuscular treatment (P < 0.05) and 0 min (range 0-180) for control treatment (P < 0.05). Motor and temperature blockade exhibited similar results. Administration of clonidine was associated with sedation and a decrease in heart rate and blood pressure independent of the route of administration. Plasma clonidine concentrations were lower for block compared to the intramuscular treatment. CONCLUSIONS: The admixture of clonidine to bupivacaine plus epinephrine prolongs and enhances brachial plexus blockade. Lower clonidine plasma concentrations for block treatment strongly suggest a local effect.

Adult↗
PubMed2004

Twelve hour reproducibility of choroidal blood flow parameters in healthy subjects.

AIMS/BACKGROUND: To investigate the reproducibility and potential diurnal variation of choroidal blood flow parameters in healthy subjects over a period of 12 hours. METHODS: The choroidal blood flow parameters of 16 healthy non-smoking subjects were measured at five time points during the day (8:00, 11:00, 14:00, 17:00, and 20:00). Outcome parameters were pulsatile ocular blood flow as assessed by pneumotonometry, fundus pulsation amplitude as assessed by laser interferometry, blood velocities in the opthalmic and posterior ciliary arteries as assessed by colour Doppler imaging, and choroidal blood flow, volume, and velocity as assessed by fundus camera based laser Doppler flowmetry. The coefficient of variation and the maximum change from baseline in an individual were calculated for each outcome parameter. RESULTS: None of the techniques used found a diurnal variation in choroidal blood flow. Coefficients of variation were within 2.9% and 13.6% for all outcome parameters. The maximum change from baseline in an individual was much higher, ranging from 11.2% to 58.8%. CONCLUSIONS: These data indicate that in healthy subjects the selected techniques provide adequate reproducibility to be used in clinical studies. Variability may, however, be considerably higher in older subjects or subjects with ocular disease. The higher individual differences in flow parameter readings limit the use of the techniques in clinical practice. To overcome problems with measurement validity, a clinical trial should include as many choroidal blood flow outcome parameters as possible to check for consistency.

Adult↗
PubMed2004

Response of choroidal blood flow to carbogen breathing in smokers and non-smokers.

AIM: To investigate a potential difference in ocular vascular reactivity during carbogen breathing in optic nerve head, choroid, and retina between healthy smokers and non-smokers. METHODS: 25 (13 smokers and 12 non-smokers) healthy male volunteers participated in this observer masked, two cohort study. During inhalation of carbogen (5% CO(2) and 95% O(2)) over 10 minutes measurements were taken using laser Doppler flowmetry to assess submacular choroidal and optic nerve head blood flow, laser interferometry to assess fundus pulsation amplitudes, and retinal vessel analyser (RVA) to assess retinal vessel diameters. RESULTS: At baseline choroidal blood flow was higher (p = 0.018, ANOVA) in smokers than in non-smokers. During administration of carbogen the response in choroidal blood flow was significantly different between the two groups: there was an increase in non-smokers after carbogen breathing (p = 0.048) compared with relatively stable blood flow in smokers (p = 0.049 between groups, ANOVA). A similar response pattern was seen for fundus pulsation amplitude, which increased notably after carbogen breathing in non-smokers but not in smokers (p<0.001 between groups, ANOVA). Optic nerve head blood flow and retinal vessel diameters were reduced in both groups to a comparable degree during carbogen breathing. CONCLUSION: The study indicated abnormal choroidal vascular reactivity in chronic smokers. These early haemodynamic changes may be related to the increased risk to smokers of developing ocular vascular diseases. The specific mechanisms underlying abnormal choroidal vascular reactivity in chronic smokers remain to be characterised.

Adult↗
PubMed2003

A randomized, double-blind, placebo controlled study on analgesic effects of botulinum toxin A.

OBJECTIVE: Botulinum toxin type A (BTXA) is used to treat neurologic disorders associated with increased muscle tone. Its use is often associated with pain relief. METHODS: A possible direct analgesic effect of BTXA on C and Adelta fibers was studied on 16 healthy volunteers receiving 30 U BTXA into one forearm and pure saline into the other. To exclude the secondary effect due to muscular tone reduction, BTXA was injected intradermally. Thermal sensory testing of heat pain (threshold and tolerance) and neuroselective current sensory testing of current pain threshold/tolerance were performed at baseline and 3, 14, and 28 days after treatment. Thereafter, on day 28, capsaicin was administered simultaneously into both forearms to evaluate a possible peripheral effect and central effect on pain processing and on the axon reflex flare. RESULTS: The authors observed no significant difference in any of the perception outcome measures between BTXA and placebo pretreated areas. Flare areas as a result of the release of neuropeptides after capsaicin application showed no differences. CONCLUSIONS: The results suggest that pain reduction after BTXA treatment is mediated through its effect on muscle tone rather than a direct analgesic effect.

Adult↗
PubMed2003

Interventions for normal tension glaucoma.

BACKGROUND: Normal tension glaucoma is a clinical condition in which the optic nerve is pathologically excavated and the visual field is disturbed. Nevertheless it has been assumed that intraocular pressure plays a role in the progression of visual field defects in this disease, but other, mainly vascular factors, have been discussed as well. OBJECTIVES: The objective of this review is to assess the effects of medical and surgical treatments for normal tension glaucoma. SEARCH STRATEGY: Trials were identified from the Cochrane Central Register of Controlled Trials (CENTRAL) (which contains the Cochrane Eyes and Vision Group trials register), MEDLINE, EMBASE and BIOSIS Previews. Bibliographies of identified trials were searched to find additional trials. In addition, investigators and pharmaceutical companies were contacted. Date of last search: January 2001. SELECTION CRITERIA: This review includes randomised controlled trials in which medical or surgical interventions were compared to no treatment, placebo or other treatment in people with normal tension glaucoma. Two reviewers independently assessed the full text copies of the possibly relevant trials. Trial quality was assessed according to the methods set out in Section 6 of the Cochrane Reviewers' Handbook (Clarke 2000). DATA COLLECTION AND ANALYSIS: Data were extracted by two reviewers and results were compared for differences. Discrepancies were resolved by discussion. The heterogeneity of interventions, follow-up periods and outcomes did not allow for statistical combinations of the study results. MAIN RESULTS: According to the selection criteria on visual field loss, eight studies were included in this review. Only three studies focussed on patient relevant outcomes. In one trial a beneficial effect of lowering intraocular pressure was found, but only if data were corrected for cataract development. In two small studies a beneficial effect on visual field loss of brovincamine, a calcium antagonist was reported. REVIEWER'S CONCLUSIONS: In one study the effect of intraocular pressure lowering on visual field outcome was only significant when data were corrected for cataract development. The results for calcium antagonists are promising, but larger trials have to be performed. Studies that focussed on reduction of intraocular pressure or haemodynamic variables are not necessarily relevant for the outcome in people with normal tension glaucoma.

Antihypertensive Agents↗
PubMed2003

Choroidal blood flow and arterial blood pressure.

PURPOSE: Untreated hypertension is associated with ocular complications and is a risk factor for the development and progression of vascular ocular pathologies. We set out to investigate the association between systemic blood pressure and choroidal blood flow. METHODS: All subjects were male non-smokers, who did not receive any medication and had normal or slightly elevated blood pressure (systolic blood pressure < or = 160 mmHg; diastolic blood pressure < or = 100 mmHg). The association between systemic blood pressure and fundus pulsation amplitude, a measure of pulsatile choroidal blood flow, was investigated in 318 volunteers. In addition, the association between systemic blood pressure and blood flow velocities in the posterior ciliary arteries supplying the choroid was investigated in these subjects. RESULTS: Ocular fundus pulsation amplitude (r = 0.252; P < 0.001) and mean flow velocity in the posterior ciliary arteries (r = 0.346, P < 0.001) were significantly associated with mean arterial pressure. The correlation of ocular haemodynamic variables with systolic and diastolic blood pressure was in the same range. CONCLUSIONS: Our data indicate a small, but significant increase in choroidal blood flow with increasing blood pressure.

Adult↗
PubMed2002

Ocular hyperperfusion following onset of intensified insulin therapy is inversely correlated with plasma endothelin-1 in Type I diabetes.

AIMS/HYPOTHESIS: It has been reported that improvement of metabolic control by intensified insulin therapy in patients with Type I (insulin-dependent) diabetes mellitus is associated with alterations in ocular blood flow. We hypothesized that these changes in ocular blood flow could be associated with alterations of plasma insulin, glucose or endothelin concentration. METHODS: In 16 patients with Type I diabetes ocular haemodynamic parameters were assessed daily during the first 5 days of institution of intensified insulin therapy and plasma concentrations of glucose, insulin, and endothelin-1 plasma were measured. Retinal white blood cell flux was estimated with the blue field entoptic technique. Pulsatile choroidal blood flow was assessed by laser interferometric measurement of fundus pulsation amplitude. RESULTS: Retinal white blood cell flux ( p=0.0015) and ocular fundus pulsation amplitude ( p<0.001) increased during institution of strict metabolic control. Changes in ocular haemodynamic variables were inversely correlated with concentrations of plasma ET-1, but not with that of insulin or glucose. CONCLUSIONS/INTERPRETATION: These data indicate that institution of improved metabolic status is paralleled by rapid changes in the production of ET-1, which could in turn affect ocular perfusion.

Adult↗
PubMed2002

Endothelin ETA receptor-subtype specific antagonism does not mitigate the acute systemic or renal effects of exogenous angiotensin II in humans.

BACKGROUND: Angiotensin II (Ang II) is assumed to play a pathophysiological role in a variety of vascular diseases. Animal studies indicate that these effects are partly attributed to stimulation of endothelin-1 (ET-1) release. The aim of the present study was to investigate whether the acute effects of Ang II on systemic and renal haemodynamics in healthy subjects can be influenced by endothelin ET(A)-receptor blockade. DESIGN: The study design was balanced, randomized, placebo-controlled, double blind, two-way cross-over, in 10 healthy male subjects. METHODS: Subjects received stepwise increasing intravenous doses of Ang II (0.65, 1.25, 2.5, 5 ng kg(-1) min(-1) for 15 min per dose level) in the presence or absence of BQ-123 (60 microg min(-1)), a specific ETA-receptor antagonist. Renal plasma flow (RPF) and glomerular filtration rate (GFR) were assessed by the para-aminohippurate and inulin plasma clearance method, respectively. Renal vascular resistance (RVR) was calculated from mean arterial pressure (MAP) and renal plasma flow. RESULTS: Ang II decreased RPF by 34% and GFR by 9% and increased RVR by 94% and MAP by 27% (ANOVA, P < 0.001 vs. baseline, for all parameters). BQ-123 did not alter these renal and systemic haemodynamic responses to a significant degree. In addition, BQ-123 had no significant haemodynamic effect under baseline conditions. CONCLUSIONS: Short-term increase of circulating Ang II levels causes systemic and renal pressor effects, which are not mitigated by endothelin ETA-receptor blockade. This suggests that the pressor response to Ang II cannot be accounted for by the acute release of vasoactive ET-1.

Adult↗
PubMed2002

Influence of diffuse luminance flicker on choroidal and optic nerve head blood flow.

PURPOSE: In the retina there is general agreement that blood flow adapts in response to different conditions of light and darkness including diffuse luminance flicker. By contrast, regulation of choroidal blood flow in response to different light conditions is still a matter of controversy. Thus, we investigated the effect of diffuse luminance flicker on choroidal and optic nerve head blood flow. METHODS: In a group of 14 healthy volunteers, choroidal blood flow and ocular fundus pulsation amplitude were assessed with laser Doppler flowmetry and laser interferometry, respectively. Measurements were done before, during and after stimulation with diffuse luminance flicker. Furthermore, the response of optic nerve head blood flow (ONHBF) to flicker stimulation was measured. Flicker stimuli were generated by a Grass PS2 photostimulator, stimulating at a frequency of 8 Hz. Flicker light consisted of light flashes at a wavelength below 550 nm and produced a retinal irradiance of 140 microW/cm( 2). Blood pressure and pulse rate were measured non-invasively. Paired t-test was used for statistical analysis. RESULTS: ONHBF increased immediately after onset of flicker stimulation. The maximum increase in ONHBF was 30% +/- 10% (mean +/- SEM, p < 0.008). Both choroidal perfusion parameters were only slightly increased during flicker stimulation, by 2 +/- 2% (laser Doppler flowmetry, p < 0.5) and by 4 +/- 1% (laser interferometry, p < 0.12). After the end of stimulation all values returned to baseline levels. CONCLUSION: Our study clearly demonstrates that diffuse luminance flicker increases optic nerve head blood flow. In contrast, increased neural activity in the retina has no effect on choroidal blood flow. Thus, choroidal blood flow appears to be largely independent of alterations in retinal metabolism.

Choroid↗
PubMed2002

Effect of inhalation of different mixtures of O(2) and CO(2) on retinal blood flow.

AIM: To determine the effects of various mixtures of O(2) and CO(2) on retinal blood flow in healthy subjects. METHODS: A randomised, double masked, four way crossover trial was carried out in 12 healthy male non-smoking subjects. Gas mixtures (100% O(2), 97.5% O(2) + 2.5% CO(2), 95% O(2) + 5% CO(2), and 92% O(2) + 8% CO(2)) were administered for 10 minutes each. Two non-invasive methods were used: laser Doppler velocimetry (LDV) for measurement of retinal blood velocity and fundus imaging with the Zeiss retinal vessel analyser (RVA) for the assessment of retinal vessel diameters. Arterial pH, pCO(2), and pO(2) were determined with an automatic blood gas analysis system. Retinal blood flow through a major temporal vein was calculated. RESULTS: Retinal blood velocity, retinal vessel diameter, and retinal blood flow decreased during all breathing periods (p <0.001 each). Administration of 92% O(2) + 8% CO(2) significantly increased SBP, MAP, and PR (p <0.001 each, versus baseline), whereas the other gas mixtures had little effect on systemic haemodynamics. Addition of 2.5%, 5%, and 8% CO(2) to oxygen caused a marked decrease in pH and an increase in pCO(2) (p <0.001 versus pure oxygen). CONCLUSIONS: Breathing of pure oxygen and oxygen in combination with carbon dioxide significantly decreases retinal blood flow. Based on these data the authors speculate that hyperoxia induced vasoconstriction is not due to changes in intravascular pH and cannot be counteracted by an intravascular increase in pCO(2).

Adult↗
PubMed2001

Ocular hemodynamics during isometric exercise.

The autoregulatory capacity of the human retina is well documented, but the pressure-flow relationship of the human choroid is still a matter of controversy. Recent data, using laser Doppler flowmetry to measure choroidal blood flow, indicate that the choroid has some autoregulatory potential, whereas most data using other techniques for the assessment of choroidal hemodynamics indicate that the choroidal pressure-flow curve is linear. We used a new laser interferometric technique to characterize choroidal blood flow during isometric exercise. Twenty healthy subjects performed squatting for 6 min during normocapnia and during inhalation of 5% CO2 and 95% air. Ocular fundus pulsation amplitude, flow velocities in the ophthalmic artery, intraocular pressure, and systemic hemodynamics were measured in 2-min intervals. To gain information on choroidal blood flow fundus pulsation amplitude was corrected for changes in flow pulsatility using data from the ophthalmic artery and for changes in pulse rate. Ocular perfusion pressure was calculated from mean arterial pressure and intraocular pressure. The ocular pressure-flow relationship was calculated by sorting data according to ascending ocular perfusion pressure values. In a pilot study in 6 healthy subjects comparable ocular pressure flow relationships were obtained when choroidal blood flow was assessed with the method described above and with laser Doppler flowmetry. In the main study isometric exercise caused a significant increase in mean arterial pressure (56%, P < 0.001), pulse rate (84%, P < 0.001), and intraocular pressure (37%, P 0.004), but decreased fundus pulsation amplitude (-36%, P < 0.001). Significant deviations from baseline choroidal blood flow were observed only at ocular perfusion pressures >69% during normocapnia and 70% during hypercapnia. Our data indicate that during isometric exercise the choroid has a high capacity to keep blood flow constant despite changes in perfusion pressure and that this pressure-flow relationship is not altered by moderate changes in arterial carbon dioxide levels.

Adult↗
PubMed2001

The renal and systemic hemodynamic effects of a nitric oxide-synthase inhibitor are reversed by a selective endothelin(a) receptor antagonist in men.

There is evidence for an interaction between nitric oxide (NO) and endothelin (ET) at the level of the renal vasculature. We hypothesized that acute renal effects of systemic NO synthase inhibition (NG-monomethyl-l-arginine, L-NMMA) may be blunted by coadministration of a specific ET(A) receptor antagonist (BQ-123) in healthy humans. Fifteen healthy young male subjects participated in this randomized, double-blind, placebo-controlled 3-way crossover study. These sodium-repleted volunteers received L-NMMA alone, or BQ-123 alone, or L-NMMA with a subsequent coinfusion of BQ-123. Renal plasma flow (RPF) and glomerular filtration rate (GFR) were determined with the PAH and inulin clearance method, respectively. Mean arterial pressure (MAP) and pulse rate were measured noninvasively at baseline and every 15 min after the start of the study period. L-NMMA alone reduced RPF (-22%, P < 0.001) and GFR (-8%, P < 0.009) and increased MAP (+10%, P < 0.001). BQ-123 alone did not affect these parameters. However, coinfusion of BQ-123 blunted the effects of L-NMMA on RPF (P < 0.001), GFR (P < 0.001), and MAP (P = 0.006). Peripheral and renal hemodynamic effects of acute systemic NO synthase inhibition are at least partially reversed by ET(A) receptor blockade with BQ-123. This indicates a functional antagonism between specific ET(A) receptor antagonist and NO synthase inhibitors at the level of the renal vasculature.

Adult↗
PubMed2001

Glucose and insulin exert additive ocular and renal vasodilator effects on healthy humans.

AIMS/HYPOTHESIS: There is evidence that insulin and glucose cause renal and ocular vasodilation. There is, however, currently no data on the effect of combined hyperglycaemia and hyperinsulinaemia on the renal and ocular blood flow seen in diabetic patients on insulin therapy. METHODS: We carried out two different 3-way crossover studies in healthy subjects (each, n = 9). In study one, hyperglycaemic clamps (5.6 mmol/l, 11.1 mmol/ 1, 16.7 mmol/l) were carried out during placebo or insulin (dose 1: 1 mU/kg/min; dose 2: 2 mU/kg/min) infusion. The second study was identical but endogenous insulin secretion was blocked with somatostatin. The renal plasma flow, glomerular filtration rate and pulsatile choroidal blood flow were measured using the paraaminohippurate method, the inulin method and a laser interferometric measurement of fundus pulsation amplitude, respectively. RESULTS: Insulin increased renal plasma flow and fundus pulsation amplitude but not the glomerular filtration rate. Hyperglycaemia increased all the renal and ocular parameters studied. Haemodynamic effects of glucose and insulin were additive when somatostatin was co-administered but not under basal conditions. CONCLUSIONS/INTERPRETATION: Glucose and insulin can exert additive vasodilator properties on renal and ocular circulation. To find out whether this observation is related to the increased regional perfusion in diabetes longitudinal studies on patients with Type I (insulin-dependent) diabetes mellitus are needed.

Adult↗
PubMed2001

Retinal blood flow and systemic blood pressure in healthy young subjects.

BACKGROUND: The aim of the present study was to investigate the association between systemic blood pressure and retinal blood flow in healthy young subjects. METHODS: Three independent study cohorts were included. A cross-sectional study was performed in 420 young male subjects with systolic blood pressure < 160 mmHg and diastolic blood pressure <100 mmHg. Retinal white blood cell flux (n=210) and blood velocity in the central retinal artery (n=210) were measured. In addition, a longitudinal study was performed in 40 young male subjects in whom retinal and systemic haemodynamic parameters were measured thrice within 6 weeks. Retinal white blood cell flux was measured with the blue-field entoptic technique. Blood flow velocity in the central retinal artery was measured by means of colour Doppler imaging. RESULTS: Retinal white blood cell flux (r=0.262; P<0.001) and mean flow velocity in the central retinal artery (r=0.174, P=0.010) were significantly associated with mean arterial pressure in the cross-sectional study. In the longitudinal study retinal white blood cell flux and mean flow velocity in the central retinal artery were also correlated with systemic blood pressure. CONCLUSIONS: Our data indicate a slight but significant increase in retinal blood flow with blood pressure. Whether this is of clinical relevance in eye diseases with altered retinal perfusion, such as diabetic retinopathy, remains to be established.

Adult↗
PubMed2001

Ocular blood flow in patients infected with human immunodeficiency virus.

PURPOSE: Alterations of ocular blood flow may play a role in the pathophysiology of human immunodeficiency virus (HIV) related retinal microvasculopathy. In this study ocular blood flow was investigated in patients with HIV infection. DESIGN: In a prospective, cross-sectional study ocular blood flow was measured in 37 eyes of consecutive HIV- infected persons and compared with the data of age-matched healthy controls. This sample size was calculated based on an alpha-error of 0.5 and a beta-error of 0.8. METHODS: Macular white blood cell flow, fundus pulsation amplitude, and blood flow velocities in the retrobulbar vessels were measured with blue field entoptic technique, laser interferometry, and Doppler sonography, respectively. Immunologic and ophthalmologic status was evaluated from each patient. RESULTS: Mean CD4+ cell count of the HIV-infected persons was 206.8 +/- 145.6 cells/mm(3). In five patients HIV-related retinopathy was observed. A significant reduction in leukocyte density was seen in HIV infected persons (82.2 +/- 23.4) as compared with the control group (102.0 +/- 28.4; P =.019). The resistive index in the central retinal artery was higher in HIV infected patients (0.77 +/- 0.05) as compared with the controls (0.74 +/- 0.04; P =.04). The other hemodynamic parameters were not different between groups. No correlation of flow parameters and CD4+ cell count or HIV-related retinopathy was observed. CONCLUSIONS: Decreased macular leukocyte density was detected in HIV infected persons. Our study suggests that abnormal retinal hemodynamics in individuals infected with HIV may be involved in the pathogenesis of HIV-related microvasculopathy.

Adult↗
PubMed2001

Unilateral light-dark transitions affect choroidal blood flow in both eyes.

There is recent evidence that the perfusion of the choroid changes during dark-light transitions. We set out to investigate this response in more detail and to elucidate possible mechanisms involved in this process. For this purpose, the effect of dark-light transitions on choroidal perfusion was studied in healthy subjects. Choroidal blood flow and ocular fundus pulsation amplitude were measured as indices of choroidal perfusion during dark-light transitions using laser Doppler flowmetry and laser interferometry, respectively. In the first experiment, subjects were first kept in room light for 20 min, then light conditions were changed to darkness for 20 min, and thereafter, subjects were exposed to room light again. Both choroidal parameters decreased (-12% to -14%) during darkness but returned to baseline after the final room light period. In the second experiment, the index eye underwent the same procedure, whereas the contralateral eye was kept in light throughout the experiment. Choroidal haemodynamic parameters in the index eye reacted in a way comparable to that seen in the first experiment. The eye that was kept in light also reacted, but the effect tended to be less pronounced than that seen in the index eye (-8% to -10%). The observation that choroidal blood flow in both eyes reacts during unilateral light-dark transitions indicates that choroidal perfusion rate is adapted to retinal illumination conditions by neural control mechanisms.

Adaptation, Ocular↗