Cold stimulation induces different responses of ophthalmic artery blood flow velocity depending on baseline blood pressure and gender.

Earlier, we have introduced the spectral index (SI), which was derived from the harmonic content of the blood flow velocity envelope of the ophthalmic artery. SI changed in dependency on the baseline blood pressure (bBP). We now examined SI during sympathetic activation by cold stimulation for 300 s in dependency on bBP to investigate the response to sympathetic neural activity in arterial hypertension. Ten men and 12 women with normal bBP (age, 60.5+/-4.6 years and 61.9+/-7.2 years) and age-adjusted men and women with increased bBP underwent the cold pressor test, including a periodical measurement of blood pressure and blood flow velocity in the ophthalmic artery, the latter by pulsed Doppler sonography. From this, the course of the SI was calculated. During cold stimulation men with increased bBP achieved their SI peak and their systolic blood pressure peak earlier than those with normal bBP (P=0.002 and P=0.035, respectively) and their SI slope was steeper than in normotensive men (P=0.002). Multiple testing showed that the difference of SI decrease between men with normal and increased bBP occurs on average 60 s after the beginning of cold stimulation (P=0.018). These differences were not found between female blood pressure groups, but the results in women may be influenced by antihypertensive treatment of some of the hypertensive women. In conclusion, the SI is useful to evaluate the response to sympathetic activation in hypertensive men but a larger study population should confirm the study results in women.

[Telemedical-supported screening of retinal vessels ("talking eyes")]. / Telemedizinisch unterstütztes Screening der retinalen Gefässe ("Talking Eyes").

BACKGROUND: Cerebral and retinal vessels behave similarly under the influence of vascular risk factors. Several groups have shown that retinal microvascular abnormalities represent an independent risk factor with regard to strokes and heart attacks. AIM OF THE STUDY: The aim of this study was to perform a prospective screening examination with regard to retinal microvascular abnormalities as well as an extended vessel diagnosis in a subgroup of patients with lower arteriovenous risk values. METHODS: In the course of a prospective cross-sectional study ("Talking Eyes") between 1.9.2001 and 1.8.2002 a telemedical-supported screening of the retina (study I) was carried out in 7,163 subjects. The patients were selected without any inclusion or exclusion criteria. The mean age was 48.2 +/- 8 years (18 - 83 years) with a sex distribution of 39.2 % females to 60.8 % males. Digital fundus photos of the right and left eyes were taken for all patients. The pictures were taken without pupil dilation using a CANON-NM camera. The pictures and case histories were stored in a central server using web-based software (MedStage, Siemens). In a central reading centre, the arteriovenous ratio of both eyes was determined telemedically using the Parr-Hubbard formula and the retinas subjected to a standardised examination by an ophthalmologist. The retinal risk factor was calculated on the basis of the arteriovenous ration, the presence of microvascular abnormalities and the case history. The reproducibility of measurement of the arteriovenous ratio (Kronbach alpha coefficient) was evaluated by double measurements on 1,332 images. In a subgroup of study I with arteriovenous ratio values < 0.76 (N = 107), an extended vessel diagnosis with measurement of 24-h blood pressure and vessel-relevant blood values (homocysteine, cholesterol, LDL, HDL, CRP, TG, HbA1c) was carried out (study II). RESULTS: Study I: The Kronbach alpha coefficient as a measure of reproducibility amounted to 0.77. The mean arteriovenous ratio of the retinal vessels was 0.83 +/- 0.09 and showed a pronounced age dependence (R = 0.9, p < 0.0001). On multivariate testing the arteriovenous ratio correlated significantly (R = 0.33, p < 0.001) with the factors age, systolic blood pressure, diastolic blood pressure and body mass index. Diastolic blood pressure followed by age had the largest influence. The prevalence of microvascular abnormalities in the right (RE) and left (LE) eyes, respectively were: cotton wool foci RE 0.0015 %, LE 0.003 %, retinal haemorrhage RE 0.1 %, LE 0.1 %, focal stenoses RE 3.4 %, LE 3.4 %, tortuositas vasorum RE 4.1 %, LE 4.0 %, arteriovenous crossing signs RE 11.2 %, LE 11.2 %. On multivariate testing the occurrence of microvascular abnormalities correlated significantly (R = 0.38, p < 0.001) with the factors high blood pressure known from case history, body mass index, and gender. Arterial hypertension had the strongest influence followed by diastolic blood pressure. The calculated retinal risk factor correlated with the prevalence of angina pectoris. Study II: 2/3 of the subjects with arteriovenous risk factor values < 0.76 exhibited pathologically high 24-h blood pressure values. For these patients there were significant correlations between the arteriovenous ratio and the low-density lipoprotein concentration as well as the Framingham risk score. CONCLUSION: In the course of a prospective, telemedical-supported screening examination of the retinal vessels of more than 7,000 subjects the arteriovenous ratio exhibited a strong dependence on age and blood pressure. Among the subjects with lowered arteriovenous ratio values, 2/3 exhibited arterial hypertension in the 24-h blood pressure determination.

Retinal microcirculation correlates with ocular wall thickness, axial eye length, and refraction in glaucoma patients.

PURPOSE: To examine the correlations of refraction, axial eye length, and posterior eye wall thickness with retinal microcirculation. PATIENTS AND METHODS: In a prospective study, 25 patients with primary open-angle glaucoma, 12 patients with ocular hypertension, and 12 healthy subjects were examined; only one eye of each participant was considered in the analysis. Posterior eye wall thickness and axial eye length were measured with standardized A-scan ultrasonography. Retinal microcirculation temporal to the optic disc was determined by a scanning laser Doppler flowmeter using automatic full-field perfusion image analyzer software. RESULTS: In glaucoma patients, temporal retinal mean flow exhibited significant correlation to the eye wall thickness (r = 0.470, P = 0.042), axial eye length (r = -0.570, P = 0.011), and refraction of the eye (r = 0.520, P = 0.022). In glaucomatous eyes, the temporal retinal mean flow was significantly lower than in healthy subjects or in ocular hypertensive patients (P = 0.01). CONCLUSIONS: Myopic eyes have longer axial eye length and thinner ocular wall than emmetropic eyes. In glaucoma patients, the longer the axial eye length and the thinner the ocular wall, the more reduced the retinal microcirculation. The reduced microcirculation found in myopic glaucomatous eyes might contribute to the development of glaucomatous damage in these eyes.

Changes in ocular blood flow velocities during external counterpulsation in healthy volunteers and patients with atherosclerosis.

BACKGROUND: External counterpulsation (ECP) is a new noninvasive means of augmenting organ perfusion by applying ECG-triggered diastolic pressure to the vascular bed of the lower limbs. In this study, effects of ECP on changes of ocular blood flow velocities were studied. METHOD: Mean, systolic and diastolic flow velocities of the ophthalmic artery were measured by Doppler sonography before and during ECP. Twelve healthy volunteers (age 31.3+/-4.3 years) and 12 patients with severe atherosclerosis (inclusion criteria: two atherosclerotic risk factors, at least one severe coronary stenosis, age 62.1+/-5.3 years) were included in the study. RESULTS: In healthy subjects, ECP changed diastolic flow velocity of the ophthalmic artery nonsignificantly from 21.6+/-7.7 to 23.7+/-10.5 cm/s. Systolic flow velocity decreased significantly from 36.1+/-13.6 to 28.9+/-10.2 cm/s (P<0.01). Mean flow velocity changed nonsignificantly from 28.1+/-9.4 to 26.5+/-9.9 cm/s. In atherosclerotic patients, mean flow velocity increased significantly from 26.3+/-11.4 to 29.3+/-11.2 cm/s (P<0.001), which was caused by significant diastolic flow augmentation from 19.7+/-9.1 to 23.9+/-9.7 cm/s (P<0.001). Systolic flow velocity was not changed significantly (from 34.2+/-12.8 to 32.6+/-11.8 cm/s). CONCLUSION: No significant change of mean blood flow velocity in the ophthalmic artery was found in young healthy subjects. In elderly patients with atherosclerosis, ECP significantly increased blood flow velocity in the ophthalmic artery by 11.4%. This may indicate an ocular perfusion benefit in these patients as a result of ECP and could also explain the increase of perfusion found in patients with retinal ischemia after ECP.

Functional imaging of the retinal microvasculature by scanning laser Doppler flowmetry.

PURPOSE: to image functionally perfused retinal vessels and to assess quantitatively the intercapillary space of the retinal microvasculature. METHOD: The base of functional imaging and the quantitative assessment of the retinal vasculature is the two-dimensional map of the retina encoded by the laser Doppler frequency shift. By Scanning Laser Doppler Flowmetry (HRF. Heidelberg Engineering) the laser Doppler frequency shift of 16.384 retinal sites (256 pixels x 64 lines, spatial resolution 10 mum) of a retinal area of 2.7 x 0.7 mm was gained. The image processing was performed by a recently described algorithm (AFFPIA). Using the data of the laser Doppler frequency shift of every retinal site, a color-coded retinal image was established showing perfused vessels and capillaries. By automatic pattern analysis of this image vessels and capillaries were identified and segmented. Based on this image the distances in [microm] of every retinal site to the next vessel or capillary were calculated ("distance to next capillary"). The functional imaging of the retinal perfusion was demonstrated in (1) normal retina, (2) retinal arterial occlusion, and (3) proliferative retinopathy. Intraobserver reliability of the quantitative assessment of the parameter "distance to next capillary" was estimated by measuring 10 eyes of 10 subjects at 5 different days by one observer. Interobserver reliability of the quantitative assessment was evaluated by analysing 10 perfusion maps by 5 different operators. In 93 eyes of 71 normal subjects (mean age 40.4 mu 15 years) the juxtapapillary retina was quantitatively evaluated. RESULTS: QUALITATIVE EVALUATION: The functional images of the retinal perfusion of eyes with normal retina, with retinal arterial occlusion, and with proliferative retinopathy corresponded well with the fluorescein angiography. Perfused vessels and capillaries became visible in a high local resolution. QUANTITITATIVE ASSESSMENT: The coefficient of reliability of the introobserver and interobserver reproducibility of the parameter 'mean distance to next capillary" was 0.74, and 0.95, respectively. The quantitative assessment of the perfusion showed that the major part of the retinal sites (>700%) had distances to the next capillary lower than 30 microm 46% of the retinal area had distances to the next capillary from 0-20 microm 26% of the retina had distances from 20-30 microm, 12% of the retina had distances from 30-40 microm 7% of the retina had distances from 40-50 microm, 4% of the retina had distances from 50-60 microm, and 4% of the retinal sites showed distances to the next capillary greater than 60 mum. The mean distance to the next capillary or vessel was calculated with 21 +/- 6.5 microm. CONCLUSION: By non-invasive Scanning Laser Doppler Flowmetry in combination with adequate software it is possible to perform a functional imaging of the retinal vasculature and to measure all index for the functional density of retinal capillaries and vessels.

[Changes in retinal blood flow by topical administration of 0.1% dipivefrin]. / Retinale Blutflussveränderungen durch topische Gabe von Dipivefrin 0.1%.

PURPOSE: Most of the antiglaucomatous drugs affect ocular blood flow. Blood flow of the anterior uvea under the effect of glaucoma medication has been described in the literature, but measurement of microcirculation at the posterior pole correlated to glaucoma medication is rarely found. We present a placebo-controlled study in which we focused on the short and long-term effects of topical dipivefrine 0.1% on the microcirculation of the retina and optic nerve head. PATIENTS AND METHODS: In a randomized, placebo-controlled double-masked study we examined 40 healthy persons (21 male and 19 female) with a mean age of 35 +/- 4.6 years. Two groups of volunteers (n = 20) were treated either with placebo or dipivefrine 0.1% for 5 days twice a day. Measurement of microcirculation was done at baseline, 30 min after the first application and on days 3 and 5. Microcirculation was evaluated by scanning-laser Doppler flowmetry (SLDF, Heidelberg Engineering; Heidelberg, Germany) [retinal and optic nerve head capillary blood flow (ONH)]. Systemic parameters were checked at all times of blood flow measurement (blood pressure, pulse); intraocular pressure (IOP) was also measured at baseline, 30 min after and on days 3 and 5. RESULTS: Systemic parameters: None of serum medications affected blood pressure or pulse. Dipivefrine 0.1% lowered the IOP significantly (P = 0.01). Microcirculation: dipivefrine 0.1% leads to a significant reduction of retinal capillary blood flow (P = 0.01). ONH blood flow was not significantly affected by dipivefrine 0.1%. CONCLUSION: Retinal capillary perfusion is affected by dipivefrine 0.1% medication. In neuroprotection, it is of interest that glaucoma medication did not alter the microcirculation in a way that leads to an increase of hypoxemia. Therefore, we consider dipivefrine 0.1% not to be useful for long-term glaucoma treatment.

Visual field defect and perfusion of the juxtapapillary retina and the neuroretinal rim area in primary open-angle glaucoma.

BACKGROUND: At this time little information is available about the relationship between glaucomatous visual field defects and impaired blood flow in the optic nerve head. The purpose of this study was to examine blood flow of the juxtapapillary retina and the rim area of the optic nerve head in primary open-angle glaucoma with a borderline visual defect. METHODS: Juxtapapillary retinal and neuroretinal rim area blood flow was measured by scanning laser Doppler flowmetry (SLDF). The visual field was evaluated by static perimetry (Octopus-G1). The optic nerve head was assessed on 15 degrees color stereo photographs. We examined 116 eyes of 91 patients with POAG with controlled IOP and 66 eyes of 44 healthy individuals. The POAG group was divided into eyes with a mean defect lower than 2 dB (POAG group I) and in eyes with a mean defect equal to or greater than 2 dB (POAG group II). The mean age of POAG group I and POAG group II was 55 +/- 11 years and 57 +/- 10 years, respectively. The mean age of the control group was 45 +/- 15 years. The eyes of POAG group I had an average C/D ratio of 0.71 +/- 0.18 with an average mean defect of the visual field of 0.97 +/- 0.68 dB; the eyes of POAG group II had an average C/D ratio of 0.80 +/- 0.17 with an average mean defect of the visual field of 8.2 +/- 6.0 dB. The intraocular pressure on the day of measurement in POAG group I was 18.2 +/- 3.7 mmHg, in POAG group II 17.6 +/- 4.0 mmHg, and in the control group 15.1 +/- 2.5 mmHg. For statistical analysis, age-matched groups of 32 normal eyes of 32 subjects (mean age 52 +/- 10 years) were compared to 18 glaucomatous eyes of 18 patients (POAG group I, mean age 55 +/- 11 years) and 59 glaucomatous eyes of 59 patients (POAG group II, mean age 55 +/- 10 years). RESULTS: In the eyes of POAG group I and POAG group II, both juxtapapillary retinal blood flow and neuroretinal rim area blood flow were significantly decreased compared to an age-matched control group: neuroretinal rim area "flow" POAG group I -65%, POAG group II -66%; juxtapapillary retina "flow" POAG group I -52%, POAG group II -44%. All eyes of the POAG group I (MD < 2 dB) and 56 of 61 eyes of the POAG group II (MD > = 2 dB) showed a retinal perfusion lower than the 90% percentile of normal blood flow. We found no correlation between reduction of juxtapapillary or papillary blood flow and mean defect in POAG eyes. CONCLUSION: Glaucomatous eyes with no defects or borderline visual field defects as well as glaucomatous eyes in an advanced disease stage show significantly decreased optic nerve head and juxtapapillary retinal capillary blood flow.

Automatic full field analysis of perfusion images gained by scanning laser Doppler flowmetry.

BACKGROUND: Scanning laser Doppler flowmetry (SLDF) enables the measurement of the laser Doppler frequency shift in retinal tissue. This process allows the quantification of retinal and optic nerve head perfusion in an area of 2.7 mm x 0.7 mm within 2 seconds and with a spatial resolution of 10 microns x 10 microns. Owing to the local heterogeneity of the retinal microcirculation itself and to heart associated pulsation the capillary retinal blood flow depends on location and time. Because of technical limitations measurements of flow are only valid in retinal points with adequate brightness and focus, and away from big vessels. To include the heart beat associated pulsation and the spatial heterogeneity of retinal blood flow into the evaluation of blood flow an algorithm was developed examining automatically the whole SLDF perfusion image. AIM: To report intraobserver reliability and interobserver reliability of a new method for analysing automatically full field perfusion images. METHOD: The base of blood flow calculation by the automatic full field perfusion image analyser (AFFPIA) was 16,384 intensity time curves of all pixels of the whole perfusion image gained by the SLDF. AFFPIA calculates the Doppler frequency shift and the haemodynamic variables flow, volume, and velocity of each pixel. The resulting perfusion image was processed with respect to (1) underexposed and overexposed pixels, (2) saccades, and (3) the retinal vessel tree. The rim area and the saccades were marked interactively by the operator. The capillaries and vessels of the retinal vessel tree were identified automatically by pattern analysis. Retinal vessels with a diameter greater than 30 microns, underexposed or overexposed areas, and saccades were excluded automatically. Based on the whole perfusion image total mean flow, total mean volume, total mean velocity, standard deviation, cumulative distribution curve of flow, and the capillary pulsation index were calculated automatically. Heart beat associated pulsation of capillary blood flow was estimated by plotting the mean capillary flow of each horizontal line against time. Intraobserver reliability was estimated by measuring 10 eyes of 10 subjects on five different days by one observer. Interobserver reliability of AFFPIA was evaluated by analysing 10 perfusion maps by five different operators. To find a baseline of retinal blood flow, perfusion maps of 67 eyes of normal subjects with a mean age of 40.4 (SD 15) years were evaluated by AFFPIA. RESULTS: The coefficient of reliability of the intraobserver reproducibility of flow was 0.74. The coefficient of reliability of the interobserver reproducibility was 0.95. The juxtapapillary retinal capillary flow was temporally 484 (SD 125), nasally 450 (117); the rim area capillary flow was 443 (110). The mean capillary pulsation index of retinal flow was 0.56 (0.14). CONCLUSION: Retinal blood flow evaluation by the AFFPIA increases significantly the interobserver reliability compared with conventional evaluation of 100 microns x 100 microns areas in SLDF images with the original Heidelberg retina flowmeter software. The intraobserver reliability of AFFPIA was in the same range as conventional evaluation.

Increased vascular resistance for venous outflow in central retinal vein occlusion.

PURPOSE: The authors quantified the vascular resistance for venous outflow in central retinal vein occlusion (CRVO). METHODS: The blood velocity in the central retinal vein (CRV) and central retinal artery (CRA) was measured by pulsed Doppler sonography (4-Mhz probe), and the pulse curve of the intraocular pressure (IOP) was evaluated by pneumotonometry. With multichannel data acquisition and storage software, the velocity-pulse curve of the CRV and CRA, the IOP-pulse curve, the arterial blood pressure, and the electrocardiogram were measured simultaneously in real-time mode. The relationships between the pulse curves of the blood velocity in the CRV and CRA and the IOP were calculated off-line. The onset time, the time of half maximum, and the time to the maximum of the pulse curves were evaluated. A relative index R' for the retinal outflow resistance was calculated by R' = deltaIOP/deltaVcrv. The authors examined 23 eyes of 23 patients with CRVO not older than 2 weeks and 23 eyes of 23 age-matched controls. There was no significant difference between the mean age of the control group (46 +/- 16 years) and that of the CRVO group (54 +/- 20 years). RESULTS: In eyes with CRVO, the authors found significantly lower systolic, diastolic, and mean outflow velocity. The amplitude of the CRV velocity pulse was significantly decreased compared with control eyes. In CRVO, the mean CRV velocity pulse amplitude (deltaVvein) was 1.77 +/- 1.0 cm/second, and in controls, it was 2.08 +/- 0.61 cm/second (P < 0.005). There was no significant difference in the mean IOP, but the IOP pulse amplitude (deltaIOP) was significantly higher in CRVO compared with controls (deltaIOP: CRVO 2.82 +/- 1.45 mmHg, control 1.96 +/- 0.56 mmHg, P < 0.005). The relative resistance index R' for venous outflow was significantly increased in eyes with CRVO (2.0 +/- 1.1 mmHg/cm/sec) compared with controls (1.1 +/- 0.44 mmHg/cm/s, P < 0.001). CONCLUSION: In eyes with CRVO, the systolic, diastolic, and mean velocity and the amplitude of the CRV velocity-pulse curve were significantly decreased and the resistance for retinal venous outflow was significantly increased compared with controls.

Relationship between ocular pulse pressures and retinal vessel velocities.

PURPOSE: The authors quantified the relationship between ocular pulse pressures and retinal vessel velocities. METHOD: The blood velocity in the ophthalmic artery (OA), the central retinal vein (CRV), and artery (CRA) was measured by pulsed Doppler sonography (4-Mhz probe). The pulse curve of the intraocular pressure (IOP) was evaluated by pneumotonometry. With multichannel data acquisition and storage software, the velocity pulse curve of the OA, the CRV and CRA, the IOP-pulse curve, the arterial blood pressure, and the electrocardiogram were recorded simultaneously in real-time mode. The relationships between the pulse curves of the blood velocity in the OA, the CRV and CRA, and the IOP were calculated off-line. The onset time, the time of half maximum, and the time to the maximum of the pulse curves were evaluated. A relative retinal venous outflow resistance index (R') was calculated by R' = deltaIOP/deltaVcrv. We examined 23 eyes of 23 healthy subjects. The mean age of the group was 46 +/- 16 years. RESULTS: In all eyes, the outflow in the CRV was pulsatile and ran in synchrony with the IOP pulsation. The CRV velocity- and IOP-pulse curve showed a significant mean delay of 0.024 second compared with the CRA and OA velocity-pulse curve. The relative resistance index R' for venous outflow was 1.0 +/- 0.44 mmHg/cm/seconds. CONCLUSION: In all eyes, the authors found a significant linear relationship between the blood velocity in the CRV and the IOP pulsation. The CRV velocity- and IOP-pulse curve were significantly delayed compared with the CRA and OA velocity-pulse curve.

Principle, validity, and reliability of scanning laser Doppler flowmetry.

PURPOSE: The objective of this study is to present the reliability and validity of scanning laser Doppler flowmetry (SLDF) performing a high-definition topography of perfused vessels of the retina and the optic nerve head with simultaneous evaluation of blood flow. METHODS: The examination of blood flow by SLDF is based on the optical Doppler effect. The data acquisition and evaluation system is a modified laser scanning device; the wavelength of the laser source is 670 mm, with a power of 100 microW (Heidelberg Engineering, HRF). The reliability of SLDF was estimated by performing five separate measurements in 10 eyes on 5 days. The validity of the method was tested by two experiments. First, in an experimental set-up, the capability of SLDF to measure the velocity of a moving plane in absolute units was estimated. Second, comparative measurements were performed of retinal blood flow in normal eyes and in 33 glaucomatous eyes with SLDF and a commercially available single-point laser Doppler flowmeter (Oculix). RESULTS: We found SLDF to produce a high reliability. The reliability coefficients r1 of flow, volume, and velocity were 0.82, 0.81, and 0.83, respectively. Comparative measurements of the retinal blood flow by SLDF and a single-point laser Doppler flowmeter of corresponding retinal points showed a linear and significant relationship between flow (r = 0.83, p < 0.0001), volume (r = 0.51, p < 0.0001), and velocity (r = 0.59, p < 0.0001). In the experimental set-up, SLDF was able to quantitatively measure velocity in absolute units. CONCLUSIONS: SLDF enables the visualization of perfused vessels of the juxtapapillary retina and the optic nerve head in high resolution by two-dimensional mapping of the optical Doppler shift and a reproducible evaluation of capillary blood flow.

Influence of age on retinal and optic nerve head blood circulation.

PURPOSE: To quantify the influence of age on the retinal perfusion, the authors investigated the microcirculation of the retina and optic nerve head (ONH) and the blood flow velocity in the central retinal artery (CRA). METHOD: The authors examined two groups of healthy volunteers. In group 1 (n=36 eyes of 36 subjects; mean age, 41.5 +/- 14.9 years), retinal and ONH microcirculation was analyzed by scanning laser Doppler flowmetry. In group 2 (n=49 eyes from 49 subjects; mean age, 44.4 +/- 15.4 years), CRA blood flow velocity was examined using pulsed Doppler sonography. RESULTS: Blood flow velocity of the CRA showed a negative correlation to age (systolic velocity, r= -0.47, P=0.001; diastolic velocity r= -0.49, P=0.001). The slope of the linear regression was -0.62 cm/second per 10 years for systolic blood velocity and -0.51 cm/second for diastolic blood velocity. Resistivity index (RI) (RI=[systolic velocity--diastolic velocity]/systolic velocity) as a marker of the rigidity of the vessel increased significantly with age (r=0.40, P=0.004). The slope was 0.03 per 10 years. Retinal microcirculation (flow omega-ret) decreased significantly with age (r= -0.63, P=0.00001). The slope was -34.9[AU] per 10 years. Optic nerve head blood flow showed no significant correlation to age (r= -0.30, P=0.071). CONCLUSION: The authors' data indicate that there is a significant decrease of retinal and CRA blood flow of approximately 6% to 11% per decade. Optic nerve head blood flow seems not to be influenced by age.