Retinal blood flow in nonischemic central retinal vein occlusion.
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Blood Flow Velocity↗
Biomedical subjects
S Orgül
Publications and source records attributed to S Orgül.
Fludrocortisone in the treatment of systemic hypotension in primary open-angle glaucoma patients.
BACKGROUND: Fludrocortisone is a potent mineralocorticoid, which has no known direct vasoactive properties, and is the first-line drug for treatment of orthostatic hypotension. The present study evaluated the systemic hemodynamic effects of fludrocortisone treatment in glaucoma patients. PATIENTS AND METHODS: A retrospective analysis of the charts of glaucoma patients of the University Eye-Clinic Basel was performed. Twenty-two patients with open-angle glaucoma under treatment with fludrocortisone were selected. The selected patients had one 24-h blood pressure recording immediately prior to treatment with fludrocortisone and one recording at least 2 months after starting the treatment. Parallel to blood pressure recordings, diurnal intraocular tension curve recordings and visual field testings were carried out. In addition, twelve patients also had nail-fold video-capillaroscopy. RESULTS: IOP and visual fields remained stable. The average values for all systemic blood-pressure readings showed an improvement in the follow-up compared to primary examination. Mean (+/- SD) night-to-day ratio ('nocturnal dips') of systolic, diastolic and mean arterial blood pressure decreased from 13.6 +/- 4.3%, 16.9 +/- 5.2% and 15.9 +/- 3.5%, respectively, to 9.9 +/- 5.9% (p = 0.01), 13.2 +/- 4.3% (p = 0.044) and 11.7 +/- 3.9% (p = 0.0004). Baseline capillary blood-flow velocity increased and capillary blood-flow standstill time after cold provocation decreased significantly under fludrocortisone therapy. CONCLUSION: Hemodynamic parameters show a tendency towards improvement in a magnitude which might be of clinical relevance.
Blood Flow Velocity↗
Is corneal temperature correlated with blood-flow velocity in the ophthalmic artery?
PURPOSE: To evaluate the correlation of blood-flow velocities in the ophthalmic artery and corneal temperature in normal subjects and glaucoma patients. METHODS: Corneal temperature was measured on both eyes by means of the THI-500 non-contact infrared thermometer in 18 healthy volunteers and in 18 age and sex matched open-angle glaucoma patients. In these subjects, blood flow velocity was assessed by means of color Doppler imaging (CDI) in both ophthalmic arteries. Peak systolic velocity (PSV), end diastolic velocity (EDV), and resistivity index (RI = [(PSV-EDV)/ PSV]) were computed. RESULTS: Corneal temperature values correlated positively with the ipsilateral values of EDV (R(2) = 0.13, p = 0.028, and R(2) = 0.16, p = 0.017 in the left and the right eyes respectively) and negatively with the ipsilateral values of RI (R(2) = 0.11, p = 0.046 and R(2 ) = 0.11, p = 0.044 in the left and the right eyes respectively) in the ophthalmic artery. In addition, the interocular difference in corneal temperature values were significantly correlated positively with the difference in EDV(R( 2) = 0.30, p = 0. 0005) and negatively with the difference in RI (R( 2) = 0.20; p: 0. 0056). All regression models were statistically comparable between normals and glaucoma patients, as well as between right eyes and left eyes. PSV did not contribute to corneal temperature. CONCLUSIONS: The present study suggests that retrobulbar hemodynamics influence corneal temperature, and that this relationship is comparable in normal subjects and glaucoma patients.
Adult↗
Relation between blood flow velocities in the ophthalmic artery and in nailfold capillaries.
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Blood Flow Velocity↗
Relationship between blood flow velocities in retrobulbar vessels and laser Doppler flowmetry at the optic disk in glaucoma patients.
The relationship between blood flow velocities in retrobulbar vessels and blood flow at the optic nerve in glaucoma patients was assessed in a prospective study. The Heidelberg retina flowmeter (HRF) was used to assess optic nerve head blood flow in 13 open-angle glaucoma patients. In the same patients, color Doppler imaging (CDI) measurements were obtained from the ophthalmic artery, the central retinal artery and the posterior ciliary arteries. Using data for one randomly selected eye per subject, correlations between HRF recordings and CDI measurements were evaluated by means of Spearman's rank correlation factor. All three HRF parameters correlated with CDI measurements obtained from retrobulbar vessels. The most marked correlations were those of the HRF parameter 'volume' with the end-diastolic velocity in the ophthalmic artery and the medial posterior ciliary artery (R = 0.79, p = 0.0012 and R = 0.81, p = 0.0007, respectively), and the peak systolic velocity in the lateral posterior ciliary artery (R = 0.82, p = 0.0006). The present study suggests that glaucoma patients with altered blood flow in retrobulbar vessels are likely to show an alteration in optic nerve blood flow as measured with the HRF.
Aged↗
Asymmetry in intraocular pressure and retinal nerve fiber layer thickness in normal-tension glaucoma.
The etiology of glaucoma is most probably multifactorial. This study intended to investigate the asymmetry in intraocular pressure (IOP) and that in retinal nerve fiber layer (RNFL) thickness in normal-tension glaucoma patients. Two diurnal tension curves, obtained within 3 months and counting at least five IOP readings each, including an early morning IOP measurement upon awaking, were obtained in 15 normal-tension glaucoma patients. None of the patients received IOP-lowering therapy. IOP asymmetry was present in at least three readings and was always in the same direction. The optic nerve was imaged in both eyes in each patient by means of confocal scanning laser ophthalmoscopy (Heidelberg Retina Tomograph). The interocular difference in RNFL thickness and the RNFL cross-sectional area were correlated with the interocular difference in IOP by means of Spearman's rank correlation factor. Nine female and 6 male normal-tension glaucoma patients (mean +/- SD age was 62. 4 +/- 16.9 years) were included in this study. Interocular IOP asymmetry varied between 0.30 and 4 mm Hg. Strong negative correlations were found between interocular asymmetry in IOP and interocular asymmetry in RNFL thickness asymmetry (R = -0.652, p = 0. 0083) and interocular asymmetry in RNFL cross-sectional area (R = -0. 702, p = 0.0034). The present results demonstrate for the first time a more marked thinning of the neuroretinal nerve fiber layer in the eye with the higher IOP in normal-tension glaucoma patients.
Chronic Disease↗
Variability in the measurement of corneal temperature using a noncontact infrared thermometer.
PURPOSE: To assess the variability of corneal temperature and the reproducibility of its measurement by means of a noncontact infrared thermometer in healthy subjects. METHODS: The THI-500 noncontact infrared thermometer (Tasco Japan, Osaka, Japan) was used for the measurement of corneal temperature. The reproducibility of corneal temperature measurements was assessed for 5 consecutive temperature readings obtained within 45 min or within 5 days. In addition, the interocular difference in corneal temperature and the diurnal temperature changes of the cornea were assessed. For each experiment, 10 healthy subjects were recruited. RESULTS: The reliability of 5 consecutive corneal temperature measurements obtained within 45 min and within 5 days was 97.92 and 85.35%, respectively. Interocular differences in corneal temperature were not statistically significant (p = 0.70). Average corneal temperature varied significantly during the day (p < 0.0001), with lower corneal temperature readings during the morning hours compared to those obtained during the afternoon. CONCLUSION: The assessment of corneal temperature by means of noncontact infrared thermometry is highly reproducible. Corneal temperature varies throughout the day, and this variation is independent of variations in environmental temperature.
Adult↗
Vascular dysregulation: a principal risk factor for glaucomatous damage?
Both intraocular pressure (IOP) and vascular factors appear to play an important role in the pathogenesis of glaucomatous optic neuropathy (GON). Arteriosclerosis and its risk factors are of minor importance, whereas vasospastic syndrome clearly is associated with GON. A vascular endotheliopathy seems to be involved in the diathetic hyperresponsiveness to stimuli, such as coldness or emotional stress. This in turn leads to a compromised autoregulation, and thereby renders the eye more sensitive to IOP or to a decrease in blood pressure. A variation in ocular perfusion may lead to an increase in free oxygen radicals. This may finally lead to apoptosis.
Animals↗
Optic nerve blood-flow abnormalities in glaucoma.
Glaucoma can be defined as an optic nerve disease with typical morphological and functional changes. There are many risk factors associated with this neuropathy. The best known factor is an increased intraocular pressure. There are, however, many other risk factors. Among them, vascular factors play a major role. Although such vascular factors have been postulated more than hundred years ago, it is only recently that the physiology and pathophysiology of the optic nerve head circulation is, to some extent, understood. New instruments have been developed to measure ocular blood flow including blood flow in the optic nerve head. Although most of the studies indicate that circulation is changed in glaucoma patients, there is little association between glaucoma and arteriosclerosis. The main cause for the circulation disturbance in glaucoma seems rather to be a vascular dysregulation leading to local vasospasm and to systemic hypotension.
Animals↗
Abnormalities of microcirculation in glaucoma: facts and hints.
Many risk factors associated with glaucoma have been identified recently. The best known of these is increased intraocular pressure (IOP). Among the others, however, vascular risk factors play a major role. Although such vascular factors were already postulated more than 100 years ago, only recent technical developments have afforded systematic investigations of associated microcirculatory disturbances and basic principles of blood flow regulation. In glaucoma, besides IOP, vascular dysregulation (such as local vasospasm and systemic hypotension, resulting in impaired autoregulation of blood flow in the optic nerve head, the choroid, and other ocular tissues) seems to be a major risk factor. However, multiple coacting factors, which are not limited to the eye but are, rather, symptoms of a systemic disease, seem to be involved in the damaging process.
Choroid↗
Endothelium-derived vasoactive substances relevant to normal-tension glaucoma.
Glaucoma is a progressive optic neuropathy that has a multi-factorial etiology. The most important risk factor is certainly an increased intraocular pressure. However, clinical observations have indicated that factors other than increased intraocular pressure also damage the neural tissue in glaucomatous optic neuropathy. The most prominent of these to be vascular dysregulation. Vascular tone is permanently regulated by a number of regulatory systems and factors, and the endothelial cell layer acts as an important mediator for the response to these factors. According to recent evidence, glaucomatous optic neuropathy may be associated with changes in endothelium-dependent vascular regulation. Consequently, therapeutic approaches based on vasodilator drugs acting via endothelium-derived substances are being developed. Although promising preliminary studies have been performed, the clinical relevance of such treatment remains to be clarified.
Animals↗
Effect of carbogen, oxygen and intraocular pressure on Heidelberg retina flowmeter parameter 'flow' measured at the papilla.
The aim of the study was to evaluate whether the Heidelberg retina flowmeter (HRF), a new device for retinal and anterior optic nerve blood flow assessment, can gauge, at least semiquantitatively, a known effect such as an increase in optic nerve blood flow by hypercapnia or a decrease in optic nerve blood flow by hyperoxia or high intraocular pressure (IOP). Measurements with the HRF were obtained at the papilla of three groups of 5 young healthy subjects (1) at baseline and after breathing 5% carbogen, (2) at baseline and after breathing 100% oxygen and (3) at baseline and after increasing IOP to 20 and 50 mm Hg. The changes in the value of the HRF parameter 'flow' were analyzed by means of a paired Student's t test. Breathing 100% oxygen for 7 min resulted in a statistically significant decrease of 34.7+/-2.5% (mean+/-SEM) in HR parameter 'flow' (p < 0.01) at the papilla. Breathing 5% carbogen for 7 min resulted in a statistically significant increase of 18.3+/-2.6% in HRF parameter 'flow' (p = 0.024). Increasing IOP to 20 mm Hg did not result in a statistically significant change in HRF parameter 'flow' (-9.6+/-7.4%; p = 0.13). Increasing IOP from 20 to 50 mm Hg, however, resulted in a statistically significant decrease of 40.1+/-6.6% in HRF parameter 'flow' (p = 0.003). With the applied stimuli, the HRF parameter 'flow' changed in the expected direction, i.e. an increase with hypercapnia and a decrease with hyperoxia or high IOP. The simplicity of use of the HRF instrument suggests that it might be well suited for a non-invasive, at least semiquantitative, assessment of changes in blood flow at the papilla.
Adult↗
Measurement of intraocular pressure with a modern noncontact tonometer.
PURPOSE: To evaluate the intraocular pressure (IOP) in a population without known glaucoma as measured by means of a noncontact tonometer (NCT). METHODS: IOP values of 842 persons, measured by means of a Pulsair 2000 NCT (Keeler Instruments, Inc., Broomhall, Pennsylvania) by 5 investigators were evaluated. Three consecutive measurements were taken first on the right eye and then on the left eye in each subject. Topical anesthesia was not used. RESULTS: The distribution of the measured IOP values was significantly different from a normal distribution. The median IOP was 15.0 mmHg (lower quartile/ upper quartile 12.5/17.2). There were no differences in IOP values between male and female subjects or between right and left eyes. There was no correlation between age and IOP values. Ninety percent of the subjects had an IOP within a range of 9-24 mmHg in both eyes. Among the examined subjects, the IOP was above 24 and 21 mmHg in 4,6 and 11%, respectively, in at least one eye. The median range of consecutive IOP measurements in one eye was 3 mmHg (lower quartile/upper quartile 2.0/4.0). The median interocular IOP difference was 1.7 mmHg (0.7/2.7). The median individual coefficient of variation (CV) values were 10.0% for the right eyes, -10.8% for the left eyes. Among the 5 different examiners, the IOP values, range of 3 consecutive IOP readings in one eye, interocular asymmetry and CV values were statistically comparable. CONCLUSION: The Pulsair 2000 NCT is very simple to use and its handling is mostly independent of the operator. The results of the present investigation might be of some value for future screening programs.
Adolescent↗
Influence of acquisition parameters on hemodynamic measurements with the Heidelberg Retina Flowmeter at the optic disc.
PURPOSE: The Heidelberg Retina Flowmeter (HRF; Heidelberg Engineering GmbH, Heidelberg, Germany) is a new instrument that determines hemodynamic variables at discrete locations of the retina and the optic disc. The objective of this study was to evaluate the influence of various HRF recording settings on the long-term variability of the HRF parameter. "Flow," computed at the optic nerve head in healthy individuals. METHODS: The authors obtained 2 sets of 5 HRF recordings in 10 healthy individuals (age range, 23-60 years). The HRF recordings were obtained within a scan area of 10 degrees x 2.5 degrees (set 1) and 20 degrees x 5 degrees (set 2). For each set, the HRF recordings were obtained on 5 consecutive days. Respective HRF recordings for both sets were obtained on the same days. On these recordings, the HRF parameter, "Flow," was computed at 3 different regions of interest (temporal superior, temporal inferior, and temporal rim of the optic disc). At all three locations, Flow was computed within windows of measurement of 10 pixels x 10 pixels and 20 pixels x 20 pixels. The effect of larger windows (30 pixels x 30 pixels, 40 pixels x 40 pixels, and 50 pixels x 50 pixels) was tested at the temporal rim of the optic disc. RESULTS: The highest reliability coefficient was reached with a scan area of 20 degrees x 5 degrees at the temporal superior rim of the optic disc (r = 0.93). Within a scan area of 20 degrees x 5 degrees, the size of the user-defined measuring window did not influence the reliability. Two models of analysis of variance disclosed that the only effect on the computed value of Flow that reached statistical significance was that because of the scan area (F = 11.172; p = 0.001). The location of the window of measurement and its size had no statistically significant effect. CONCLUSION: The present results show that the location of the window of measurement has an important effect on the long-term variability of the HRF parameter, Flow. In addition, different scan areas influence significantly the computed values of this parameter.
Adult↗
Descriptive information of topographic parameters computed at the optic nerve head with the Heidelberg retina tomograph.
PURPOSE: To analyze the frequency distribution and descriptive information of topometric data obtained with the Heidelberg Retina Tomograph (HRT) in a normal population. METHODS: Topographic measurements of the optic disc were acquired and evaluated using the HRT in 225 subjects between 12 and 90 years of age. After randomly selecting one eye per subject, the frequency distributions, mean values, minima, maxima, and first, fifth, fiftieth, ninety-fifth, and ninety-ninth percentiles were evaluated for topographic parameters computed by the HRT. The influence of age, intraocular pressure (IOP), disc size, and disc shape on optic disc topometric data was analyzed. A principal component analysis of the topometric parameters was performed. The frequency distributions, mean values, minima, maxima, and first, fifth, fiftieth, ninety-fifth, and ninety-ninth percentiles of the interocular difference in topographic parameters were evaluated. RESULTS: All topographic parameters showed a unimodal but not necessarily normal distribution. None of the parameters showed a relevant correlation with age, IOP (in the normal range), and overall shape of the anterior optic nerve, but a few parameters showed a clinically significant correlation with disc size. A principal component analysis identified four relevant factors (optic nerve cup, retinal nerve fiber layer, optic disc size, and optic nerve cup shape) in the entire data set of optic nerve topometric data. The absolute value of all interocular differences in topographic parameters showed an asymmetric but unimodal distribution. CONCLUSION: The mathematical description of the optic nerve cup shape provides information on optic nerve head topography independently from cupping, nerve fiber layer thickness, and disc size. Potentially, quantification of further aspects in optic nerve head topography might improve the discriminatory power of computerized quantitative optic nerve head analysis.
Adolescent↗
Variability of contour line alignment on sequential images with the Heidelberg Retina Tomograph.
BACKGROUND: The influence of the contour line alignment software algorithm on the variability of the Heidelberg Retina Tomograph (HRT) parameters remains unclear. METHODS: Nine discrete topographic images were acquired with the HRT from the right eye in six healthy, emmetropic subjects. The variability of topometric data obtained from the same topographic image, analyzed within different samples of images, was evaluated. A total of four mean topographic images was computed for each subject from: all nine discrete images (A), the first six of those images (B), the last six of those nine images (C), and the first three combined with the last three images (D). A contour line was computed on the mean topographic image generated from the nine discrete topographic images (A). This contour line was then applied to the three other mean topographic images (B, C, and D), using the contour line alignment in the HRT software. Subsequently, the contour line on the mean topographic images was applied to each of the discrete members of the particular images subsets used to compute the mean topographic image, and the topometric data for these discrete topographic images was computed successively for each subset. Prior to processing each subset, the contour line on the discrete topographic images was deleted. This strategy provided a total of three analyses on each discrete topographic image: as a member of the nine images (mean topographic image A), and as a member of two subsets of images (mean topographic image B, C, and/or D). The coefficient of variation (100 x SD/mean) of the topographic parameters within those three analyses was calculated for each discrete topographic image in each subject ("intraimage" coefficient of variation). In addition, a coefficient of variation between the nine discrete topographic images ("interimage" coefficient of variation) was calculated. RESULTS: The "intraimage" and "interimage" variability for the various topographic parameters ranged between 0.03% and 3.10% and between 0.03% and 24.07% respectively. The "intraimage" coefficients of variation and "interimage" coefficients of variation correlated significant (r2 = 0.77; P < 0.0001). CONCLUSION: A high "intraimage" variability, i.e. a high variability in contour line alignment between sequential images, might be an important source of test re-test variability between sequential images.
Adult↗
Sources of variability of topometric data with a scanning laser ophthalmoscope.
OBJECTIVE: To determine in a two-part study whether misalignment between the patient and the laser scanner is a major source of variability with the Heidelberg Retina Tomograph (Heidelberg [Germany] Engineering). METHODS: Three topographic images of the right optic nerve were acquired with the Heidelberg Retina Tomograph in eight patients with glaucoma. The correlations between average cup volume, variability of cup volume estimates, and direction of imaging were evaluated. Furthermore, the correlations between average rim volume, variability of rim volume estimates, and direction of imaging were evaluated. Next, the optic nerve cup volume and rim volume estimates of a rabbit's left eye were compared between three series of five topographic images acquired from three slightly different directions. RESULTS: Average cup volume, variability of cup volume estimates, and variability in the direction of imaging correlated significantly among the patients with glaucoma (multiple R2 = .95; P < .001). Average rim volume, variability of rim volume estimates, variability in the direction of imaging, and variability in the mean height of the contour line also correlated significantly (multiple R2 = .88; P = .03). In the rabbit eye, the cup volume and the rim volume differed significantly among the three image series (analysis of variance, P < .001 and P = .04, respectively). CONCLUSION: Misalignment between the patient and the laser scanner may account for significant variability with the Heidelberg Retina Tomograph.
Animals↗
Measurement of optic nerve blood flow with nonradioactive colored microspheres in rabbits.
The objective of this study was to establish a nonradioactive technique to accurately assess blood flow in a small tissue such as the anterior optic nerve. Colored microspheres, 10.2 +/- 0.23 microns in diameter, were injected into the left atrium in each of 17 anesthetized rabbits. The rabbits were divided into four groups injected, respectively, with 5, 10, 50, or 100 million microspheres. Microsphere quantification in the tissue was performed after postmortem dissection and alkaline corrosion of the anterior optic nerve. Blood flow was evaluated by means of reference sample comparison method. While the relative interocular difference (range, 15.3-162.8%) was not significantly different between the rabbits injected with 5, 10, or 50 million microspheres (Kruskal-Wallis test, P = 0.11), injection with 100 million microspheres yielded a significantly lower relative interocular differences (range 2.3-12.8%) compared to the other three groups (Kruskal-Wallis test, P = 0.0048). In addition, reproducibility of microsphere counts was evaluated by ranking the difference between right and left optic nerve in percentage of the average number of microspheres per milligram of tissue in both optic nerves. The correlation between the relative interocular difference (range, 2.3-162.8%) and the average number of microspheres per milligram of tissue (1.2-78.7 microspheres/mg optic nerve tissue) was statistically significant (Spearman R, -0.90; P < 0.0001). The interocular variability in microsphere counts and interocular difference in intraocular pressure did not correlate (Spearman R, 0.33; P = 0.20). The rabbits injected with 100 million microspheres showed the highest average number of microspheres (range, 31.8-78.7 microspheres/mg optic nerve tissue). The optic nerve blood flow ranged between 0.14 and 0.24 microliters/mg/min among the rabbits injected with 100 million microspheres. The present experimental technique of optic nerve blood flow measurement is relatively inexpensive, highly reproducible, and obviates disposal of radioactive materials.
Animals↗