Ocular Perfusion Pressure (ocular + perfusion_pressure)

Distribution by Scientific Domains


Selected Abstracts


Autoregulation in the choroid

ACTA OPHTHALMOLOGICA, Issue 2009
S ORGUL
Purpose To compare subfoveal choroidal blood flow (ChBF) in sitting and supine position in normal volunteers. Methods ChBF was measured with laser Doppler flowmetry in 22 healthy volunteers (mean age SD: 24 5 years). Six independent measurements of choroidal blood flow were obtained in one randomly selected eye of each subject. Subsequently, the subjects assumed a supine position for 30 minutes and a new series of 6 measurements was obtained. Parallel hereto, systemic blood pressure and intraocular pressure were measured. Ocular perfusion pressure (OPP) was calculated based on formulas derived from ophthalmodynamometric studies. The influence of changing OPP on the change in ChBF was assessed in a linear regression analysis. Results The coefficient of variation for ChBF was 10.28% and 9.58% in the sitting and the supine position respectively. ChBF decreased by 6.6% (p=0.0017) in the supine position. The estimate for ophthalmic blood pressure in the supine position was adjusted to obtain a result of no change in OPP for no change in ChBF, yielding an average decrease for the estimate of OPP of 6.7% (p=0.0002). Change in OPP correlated significantly with change in ChBF (R2: 0.20; p=0.036) with a slope for the regression line of 1.04. Conclusion The comparable degree of change in ChBF and OPP and the linear relationship between the two parameters suggest a passive response of the choroidal circulation to the posture change. In contrast, the OPP estimates suggest a marked buffering of the change in perfusion pressure by the carotid system, compatible with a close control of the gradient in perfusion pressure between the heart and its branches within the carotid system. [source]


Association between optic nerve head blood flow as assessed with Laser Doppler Flowmetry and mean arterial blood pressure in glaucoma, ocular hypertension and healthy control subjects

ACTA OPHTHALMOLOGICA, Issue 2009
D SCHMIDL
Purpose It has been implicated that vascular dysregulation plays a role in the pathogenesis of primary open angle glaucoma (POAG). In the present study the association between optic nerve head blood flow as measured with laser Doppler flowmetry and ocular perfusion pressure in patients with treated and untreated POAG, patients with ocular hypertension and healthy control subjects was compared. Methods 136 patients with treated POAG, 116 patients with untreated POAG, 138 patients with ocular hypertension and 160 control subjects were included in the study. Optic nerve head blood flow was assessed using laser Doppler flowmetry. Ocular perfusion pressure was calculated based on measurement of IOP and systemic hemodynamics. Results Optic nerve head blood flow was significantly reduced in patients with glaucoma compared to patients with ocular hypertension and healthy subjects (p<0.01). However, no difference in optic nerve head blood flow between treated and untreated glaucoma patients was detected. The highest association between ocular perfusion pressure and optic nerve head blood flow was found in untreated glaucoma patients followed by ocular hypertensives and treated glaucoma patients. Conclusion The present study confirms evidence that optic nerve head blood flow is reduced in patients with POAG and patients with ocular hypertension. Correlation coefficients in the glaucoma groups and in the ocular hypertensives indicate a vascular dysregulation in these patients compared to healthy control subjects. [source]


2224: Oxygenation of the human retina

ACTA OPHTHALMOLOGICA, Issue 2010
E STEFANSSON
Purpose Partial pressure of oxygen in the optic nerve and retina is regulated by the intraocular pressure and systemic blood pressure, the resistance in the blood vessels and oxygen consumption of the tissue. The PO2 is autoregulated and moderate changes in intraocular pressure, blood pressure or tissue oxygen consumption do not affect the retinal and optic nerve oxygen tension. Methods If the intraocular pressure is increased above 40 mmHg or the ocular perfusion pressure decreased below 50 mmHg the autoregulation is overwhelmed and the optic nerve becomes hypoxic. The levels of perfusion pressure that lead to optic nerve hypoxia in the laboratory correspond remarkably well to the levels that increase the risk of glaucomatous optic nerve atrophy in human glaucoma patients. Medical intervention can affect optic nerve PO2. Lowering the intraocular pressure tends to increase the optic nerve PO2, even though this effect may be masked by the autoregulation when the optic nerve PO2 and perfusion pressure is in the normal range. Results Carbonic anhydrase inhibitors increase retinal PO2 through a mechanism of vasodilatation and lowering of the intraocular pressure. Carbonic anhydrase inhibition reduces the removal of CO2 from the tissue and the CO2 accumulation induces vasodilatation resulting in increased blood flow and improved oxygen supply. This effect is inhibited by indomethacin but not other cyclo-oxygenase inhibitors. Conclusion Carbonic anhydrase inhibitors increase retinal blood flow and increase oxygen delivery. Glaucoma drugs and glaucoma surgery lower intraocular pressure, increase ocular perfusion pressure and blood flow. Demand of oxygen by retinal cells may be reduced through apoptosis and tissue atrophy, as well as active destruction of tissue by laser photocoagulation. [source]


2323: Role of nitric oxide in optic nerve head blood flow regulation during isometric exercise in healthy humans

ACTA OPHTHALMOLOGICA, Issue 2010
D SCHMIDL
Purpose Nitric oxide (NO) is an important regulator of optic nerve head (ONH) blood flow in humans. We have previously shown that NO is also involved in choroidal blood flow regulation during isometric exercise. Inhibition of NO synthase (NOS) has been reported to shift choroidal pressure,flow curves during squatting to the right. The hypothesis for the present study was that inhibition of NOS may also influence ONH blood flow during isometric exercise. Methods To test this hypothesis, a randomized, double-masked, placebo-controlled, three-way crossover study was performed in 18 healthy volunteers. Subjects received on different study days intravenous infusions of NG-monomethyl- L-arginine (L-NMMA), phenylephrine, or placebo. During these infusion periods, subjects were asked to squat for 6 minutes. ONH blood flow was assessed with laser Doppler flowmetry, and ocular perfusion pressure (OPP) was calculated from mean arterial pressure and intraocular pressure. Results L-NMMA and phenylephrine increased resting OPP (p < 0.001 versus baseline), but only L-NMMA reduced resting ONH blood flow (p = 0.02 versus baseline). The relative increase in OPP during isometric exercise was comparable with all drugs administered (p = 0.69). In addition, the change of ONH blood flow was comparable with all administered drugs (p = 0.43). Conclusion These data indicate that NO plays an important role in the regulation of ONH blood flow at baseline, but does not change the response of ONH blood flow during isometric exercise. [source]


2326: Influence of change in body position on choroidal blood flow in patients with obstructive sleep apnea syndrome

ACTA OPHTHALMOLOGICA, Issue 2010
A ALMANJOUMI
Purpose Obstructive sleep apnea syndrome (OSA) has been reported to be associated with ischemic and glaucomatous optic neuropathy (especially normal tension glaucoma). OSA per se is able to generate hypertension, atherosclerosis and autonomic dysfunction, all conditions possibly interacting with ocular vascular regulation. The aim of our study was to characterize the choroidal vascular reactivity to change in body position in OSA patients, as compared with matched healthy control subjects. Methods Eighteen newly diagnosed OSA patients were included in this prospective study. Control subjects were matched with OSA patients for body mass index (BMI), gender and age. At the screening visit, each subject underwent a general exam, cardiovascular, neurologic and ophthalmological examinations, and overnight polysomnography. The LDF instrument used in this study to measure subfoveal choroidal blood flow (ChBF), ChBVel , velocity (kHz); and volume, ChBVol (in arbitrary units, AU) Vascular choroidal reactivity was tested during the change in body position from the sitting to the supine position (10 min). Results OSA patients exhibited a similar choroidal reactivity during change in body position than controls with increased ChBVel (+15%), decreased ChBVol (-11.6%), and unchanged ChBF. IOP increased by 14.2% in the supine position whereas ocular perfusion pressure remained stable. Conclusion This prospective comparative study showed for the first time unimpaired choroidal vascular reactivity in otherwise healthy OSA patients. This suggests OSA patients, without comorbidities, has long-term adaptive mechanisms active in ocular microcirculation. [source]


Effect of acute postural variation on diabetic macular oedema

ACTA OPHTHALMOLOGICA, Issue 2 2010
Martin Vinten
Abstract. Purpose:, This study aimed to study the pathophysiology of diabetic macular oedema (DMO) by analysis of concomitant changes in macular volume (MV), mean arterial blood pressure (MABP), intraocular pressure (IOP), and retinal artery and vein diameters in response to acute postural changes in patients with DMO and healthy subjects. Methods:, Thirteen patients with DMO (13 eyes) and five healthy subjects (five eyes) were examined after resting in a chair for 15 mins using optical coherence tomography to measure MV and fundus photography to assess retinal vessel diameters. The patients then lay down for 60 mins, during which they were examined repeatedly before they were reseated and examined again. Intraocular pressure was measured using pulse-air tonometry, arterial blood pressure by sphygomanometry and fluid columns using rulers and a spirit level. Results:, In healthy subjects, retinal artery (p = 0.02) and vein (p = 0.001) diameters decreased when subjects lay down, whereas MV remained stable. In patients with DMO, no orthostatic variation in retinal vessel diameters could be demonstrated, whereas MV had increased by 2.4 0.6% (mean standard error of the mean; p = 0.006) 50 mins after assuming a recumbent position. In both healthy subjects and DMO patients, MABP decreased and IOP increased in a recumbent position, with no significant difference between the groups. Conclusions: The increase in MV that occurs in DMO when changing from a seated to a recumbent position is associated with a failure of retinal artery contraction, a response seen in healthy subjects that appears to counter-regulate the increase in ocular perfusion pressure caused by assuming a recumbent position. [source]


Changes in optic nerve head blood flow induced by the combined therapy of latanoprost and beta blockers

ACTA OPHTHALMOLOGICA, Issue 7 2009
Tetsuya Sugiyama
Abstract. Purpose, To assess the effects of combined therapy with latanoprost and beta blockers on optic nerve head (ONH) blood flow in normal-tension glaucoma (NTG) patients. Methods, Intraocular pressure (IOP), ONH blood flow (laser speckle flowgraphy) and blood pressure were measured in 15 eyes of 15 NTG patients (41,76 years old) before treatment or after a 1-month washout period. Similar measurements were performed at 2 months after the commencement of treatment with latanoprost and at 3 months after the start of combined therapy of latanoprost with 0.5% timolol or 2% carteolol in a crossover study using the envelope method. Measurement was carried out 2,3 hr after the morning application of eyedrops. Results, Latanoprost decreased IOP with no significant change in ONH blood flow. Concomitant use of timolol or carteolol further decreased IOP with no significant difference between these two drugs. Only the combined therapy of latanoprost with carteolol significantly (p < 0.01) increased ONH blood flow by approximately 10%, compared to initial levels. There was no significant change in mean blood pressure, ocular perfusion pressure or pulse rate as a result of these therapies. Conclusion:, Topical latanoprost,carteolol combined therapy increased ONH blood flow in NTG patients, unlike latanoprost,timolol therapy. Because ocular perfusion pressure was unchanged, direct vasodilative effects were suspected as the mechanism. [source]


Complex regulation of choroidal blood flow during combined changes in blood pressure and IOP

ACTA OPHTHALMOLOGICA, Issue 2009
L SCHMETTERER
Purpose In the recent years it has been shown that the human choroid shows some regulatory capacity during an artifical increase in intraocular pressure (IOP) as well as during an exercise induced increase in mean arterial pressure (MAP). The purpose of the present study was to test the hypothesis that human choroidal blood flow (ChBF) may depend, not only on ocular perfusion pressure (OPP), but also on absolute levels of MAP and IOP. Methods In a clinical study in 28 helathy subjects OPP was varied by elevating IOP during a squatting-induced increase in MAP. IOP was raised in stepwise increments by using the suction cup method. Subfoveal choroidal blood flow (VhBF, laser Doppler flowmetry), MAP, and IOP were assessed, and OPP was calculated as (2/3)(MAP - IOP). For correlation analysis, data from all subjects were pooled according to IOP and MAP values, and correlation analyses were performed. Results When data were grouped according to IOP, no correlation was observed between ChBF and MAP; but ChBFs were lower, the higher the IOP (P < 0.001). When data were grouped according to MAP, a significant correlation was found between ChBF and IOP (P < 0.001), but correlations were independent of MAP. Conclusion These data confirm previously published observations that the choroid shows some regulatory capacity during changes in OPP. In addition, the data indicate that the choroid regulates its blood flow better during exercise-induced changes in MAP than during an experimental increase in IOP. [source]


Ocular blood flow autoregulation and the clinical implications of its alteration

ACTA OPHTHALMOLOGICA, Issue 2009
G GARHOFER
Autoregulation is commonly defined as the ability of a vascular bed to adapt blood flow to changes in ocular perfusion pressure (pressure autoregulation) or to adapt to changes in metabolic need (metabolic autoregulation). Considering the high metabolic turnover of the eye, its intact function is strongly dependent on a stable blood supply, assured by an intact vascular autoregulation. However, it has been shown that in the recent years that several ocular diseases such as glaucoma, diabetic retinopathy or age related macula degeneration are associated with an impaired autoregulation. This vascular dysregulation may lead to an under- or overperfusion of the tissue and in turn to ischemia and/or oxidative stress. This talk seeks to summarize our current knowledge of autoregulation in the ocular vascular beds. Furthermore, the possible reasons of impaired autoregulation and how this may relate to ocular pathologies will be discussed. [source]


Impact of medication on ocular blood flow

ACTA OPHTHALMOLOGICA, Issue 2009
L SCHMETTERER
Purpose Reduced ocular blood flow appears to play a role in the pathophysiology of glaucoma. Hence, there is considerable interest in drugs that are capable of improving ocular perfusion. Methods A large numer of clinical trials have been performed investigating the ocular hemodynamic effects of topical and systemic medications. Such trials used a variety of different methods to assess ocular blood flow parameters. Results When adminsitered systemically most vasodilators decrease systemic blood pressure thereby reducing ocular perfusion pressure (OPP). Only few classes of drugs have been reported to increase ocular blood flow with no or minimal effect on OPP. Among these carbonic anhydrase inhibitors and endothelin receptor anatgonists show the most prononced ocular vasodilator effects. The ocular hemodynamoic effects of topical medications is generally considered small. Conclusion When drugs are given systemically the effects on OPP have to be considered. In addition, the potentially positive effects on ocular perfusion need to be carefully weighed against the side effects. With topically administered drugs the ocular hemodynamic effects will be generally small, because the drugs reach the posterior pole of the eye in small concentrations only. [source]


Evidence for altered ocular rigidity in glaucoma

ACTA OPHTHALMOLOGICA, Issue 2009
L SCHMETTERER
Purpose Based on theoretical models and animal studies altered biomechanical properties of the optic nerve head and the sclera have been implicated in the pathophysiology of glaucoma. Only few data have, however, demonstrated such biomechanical alterations in vivo. We tested the hypothesis that patients with primary open angle glaucoma (POAG) have an abnormal structural stiffness based on measurements of intraocular pressure amplitude and ocular fundus pulsation amplitude. Methods Seventy patients with POAG and 70 healthy control subjects matched for age, gender, intraocular pressure and systemic blood pressure were included in this study. The ocular pulse amplitude (PA) was assessed with pneumotonometry. The fundus pulsation amplitude (FPA) was measured using laser interferometry. Based on the Friedenwald equation a coefficient of structural stiffness (E1) was calculated relating PA to FPA. Results Systemic blood pressure, intraocular pressure, and ocular perfusion pressure was comparable between glaucoma patients and healthy control subjects. FPA as well as PA was lower in patients with glaucoma than in healthy controls. The calculated factor E1 was significantly higher in patients with POAG (0.0454 0.0085 a.u.) than in healthy control subjects (0.0427 0.0058 a.u., p = 0.03). Conclusion This study is indicative of increased structural stiffness of the sclera in patients with POAG. This is in agreement with a number of previous animal experiments and supports the idea that the biomechanical properties of ocular tissues play a role in the process of glaucomatous ONH damage. [source]


Association between optic nerve head blood flow as assessed with Laser Doppler Flowmetry and mean arterial blood pressure in glaucoma, ocular hypertension and healthy control subjects

ACTA OPHTHALMOLOGICA, Issue 2009
D SCHMIDL
Purpose It has been implicated that vascular dysregulation plays a role in the pathogenesis of primary open angle glaucoma (POAG). In the present study the association between optic nerve head blood flow as measured with laser Doppler flowmetry and ocular perfusion pressure in patients with treated and untreated POAG, patients with ocular hypertension and healthy control subjects was compared. Methods 136 patients with treated POAG, 116 patients with untreated POAG, 138 patients with ocular hypertension and 160 control subjects were included in the study. Optic nerve head blood flow was assessed using laser Doppler flowmetry. Ocular perfusion pressure was calculated based on measurement of IOP and systemic hemodynamics. Results Optic nerve head blood flow was significantly reduced in patients with glaucoma compared to patients with ocular hypertension and healthy subjects (p<0.01). However, no difference in optic nerve head blood flow between treated and untreated glaucoma patients was detected. The highest association between ocular perfusion pressure and optic nerve head blood flow was found in untreated glaucoma patients followed by ocular hypertensives and treated glaucoma patients. Conclusion The present study confirms evidence that optic nerve head blood flow is reduced in patients with POAG and patients with ocular hypertension. Correlation coefficients in the glaucoma groups and in the ocular hypertensives indicate a vascular dysregulation in these patients compared to healthy control subjects. [source]


Assessment of the spontaneous pulsations of the central retinal vein in daily ophthalmic practice

CLINICAL & EXPERIMENTAL OPHTHALMOLOGY, Issue 9 2007
Ulrich Legler MD
Abstract The purpose of this study is to assess the frequency of eyes with a spontaneous pulsation of the central retinal vein in the setting of a busy daily ophthalmic practice. The clinical observational case-series study included 690 eyes (345 subjects). The optic disc was ophthalmoscopically assessed using a non-contact ophthalmoscopic lens at the slit lamp. Out of the study population, 526 eyes (76.2%) of 265 (76.8%) subjects showed a detected spontaneous pulsation of the central retinal vein (prevalence rate: 76.2 1.6% [mean standard error] per eye, and 76.8 2.3% per subject). In univariate analysis, the presence of a detected spontaneous central retinal vein pulsations was statistically associated with systolic systemic blood pressure (P = 0.04) and with the ocular perfusion pressure (P = 0.03). The results suggest that as examined in the setting of a busy daily ophthalmic practice, the central retinal vein was found to show a spontaneous pulsation in about 80% of the subjects. [source]