Retinal Artery Blood Flow Velocities Research Articles

Flickering light increases retinal blood flow.

To examine the retinal blood flow in normal eyes before and during retinal stimulation by flickering light. A prospective cross-sectional study. PARTICIPANTS AND TESTING: Twenty-seven eyes of 27 normal subjects with a mean age +/- SD of 38 +/- 15 years (study I) and 21 eyes of 21 normal subjects with a mean age +/- SD of 46 +/- 17 years (study II) were examined with respect to capillary retinal blood flow and central retinal artery and central retinal vein blood flow velocities during flickering light stimulation. A luminance flicker light with a frequency of 8 Hz increased the neuronal activity of retinal ganglion cells. In study I, the retinal capillary blood flow was measured before and during flickering by scanning laser Doppler flowmetry (670 nm, Heidelberg Retina Flowmeter). In study II, the blood flow velocities in the central retinal artery and central retinal vein were examined by pulsed Doppler sonography. Change in blood flow velocities in the central retinal artery and vein and in retinal capillary blood flow after full-field flicker stimulation. In study I, measurements of blood flow during retinal flicker stimulation showed a significant increase in the mean value of blood flow +/- SD from 317 +/- 72 arbitrary units to 416 +/- 103 arbitrary units. The change was on average 46 +/- 19%. In study II, the systolic and end-diastolic blood flow velocities in the central retinal artery increased significantly (P < 0.0001): systolic, 9 cm/s to 15 cm/s (+62%); end-diastolic, 2.7 cm/s to 5.3 cm/s (+96%). In the central retinal vein, the systolic and end-diastolic blood flow velocities increased significantly (P < 0.0001): systolic, 4.3 cm/s to 6.7 cm/s (+56%); end-diastolic, 1.8 cm/s to 3.6 cm/s (+100%). The authors found no significant change in blood pressure and heartbeat frequency. Visual stimulation of the retina by flickering light strongly increased the juxtapapillary retinal capillary blood flow and central retinal artery blood flow velocity in normal eyes.

Normal neonatal values of ophthalmic and central retinal artery blood flow velocities.

To define standard values of blood flow velocities and indices in the ophthalmic and central retinal arteries in the neonatal period. Forty-two healthy full-term neonates comprised the study population. A color Doppler with mechanical sector probe was used for measuring blood flow velocity in the ophthalmic and central retinal arteries. Systolic, end diastolic, and mean-enveloped velocities were measured, and the resistance index and pulsatility index were calculated. Ophthalmic artery Doppler velocities were similar on the first and third days of life, but increased significantly on the fifth and seventh days of life; resistance index significantly increased during the first week of life, whereas pulsatility index did not change significantly. Doppler velocities of the central retinal artery were similar on the first and third days; they show a delayed increase compared to the ophthalmic artery. Central retinal artery blood flow velocities increased significantly from the third to seventh postnatal day. Resistance index also increased between the first two days and on the fifth and seventh postnatal days, while pulsatility index did not change. These data constitute a starting point for studying the possible relationship between eye circulation and pathogenesis of retinopathy of prematurity.

Doppler ultrasound of blood flow velocities in ophthalmic and central retinal arteries during the early neonatal period

PURPOSE: To obtain standard values of blood flow velocity in the ophthalmic artery and central retinal artery in the neonatal period and to compare blood flow velocity of orbital vessels with that of the anterior cerebral artery and middle cerebral artery. METHODS: Forty-five healthy neonates (gestational age, 39.2 ± 1.2 weeks; birth weight, 3,210 ± 567 g) on the first and third postnatal days (90 eyes each time) and on the fifth day of life (34 eyes) were included in a clinical trial. A duplex scanner with mechanical sector probe was used for measuring blood flow velocity in the ophthalmic artery, central retinal artery, anterior cerebral artery, and middle cerebral artery. A nominal imaging frequency of 7.5 MHz, a transmitted Doppler frequency of 5 MHz, and a wall filter setting of 50 Hz were used in each case. Systolic, end-diastolic, and mean-enveloped velocities were measured for the studied vessels and the resistance and pulsatility indices were calculated. RESULTS: On the first postnatal day, blood flow velocities and indices in the ophthalmic artery were systolic 14 ± 2.4 cm/sec, end-diastolic 3.8 ± 0.6 cm/sec, mean-enveloped 7.3 ± 1.3 cm/sec, resistance index 0.73 ± 0.03, and pulsatility index 1.5 ± 0.2. Central retinal artery blood flow velocities and indices were systolic 8.7 ± 1.8 cm/sec, end-diastolic 2.7 ± 0.7 cm/sec, mean-enveloped 5.0 ± 1.1 cm/sec, resistance index 0.70 ± 0.04, and pulsatility index 1.3 ± 0.1. There were no significant differences in ophthalmic artery and central retinal artery flow velocities between right and left eyes. Doppler values of the central retinal artery were significantly lower ( P = .0005) than those of the ophthalmic artery for each day studied. The Doppler data for the central retinal artery and ophthalmic artery were significantly lower (from P = .005 to .0001) than those observed in the anterior cerebral artery and middle cerebral artery at the same postnatal age. No significant differences in flow variables were found in the central retinal artery and ophthalmic artery from the first to third day, whereas blood flow velocities in the anterior cerebral artery and middle cerebral artery increased significantly ( P = .01 to .0001) from day 1 to day 3. On the fifth day of life a significant increase in blood flow velocities and indices was observed in the ophthalmic artery, whereas only systolic velocity significantly increased in the central retinal artery. CONCLUSIONS: We report blood flow data of the ophthalmic artery and central retinal artery in healthy neonates and suggest that a delay of arterial blood flow changes occurs for the ophthalmic artery and central retinal artery with respect to the anterior cerebral artery and middle cerebral artery in the early prenatal period.

Altered retrobulbar vascular reactivity in early diabetic retinopathy

AIM/BACKGROUNDIn diabetic eye disease the factors leading to compromised circulation and the resulting loss of visual function are poorly understood. Although retinal circulation has been widely investigated, it accounts for...

Successful Scleral Buckling Procedures Decrease Central Retinal Artery Blood Flow Velocity

Limited data suggest that scleral buckling procedures may decrease posterior segment blood flow. How this may affect functional outcome remains unknown. In a prospective, controlled study, color Doppler imaging was used to measure blood flow velocities in the central retinal and ophthalmic arteries of both eyes in patients with unilateral rhegmatogenous retinal detachments before and after primary scleral buckle repair. Encircling elements were used in all patients. Fellow eyes served as controls. Data from six consecutive patients did not show significant preoperative circulatory abnormalities in either artery compared with the controls. There was a statistically significant reduction in mean central retinal artery blood flow velocities of up to 53% in the immediate postoperative period. Ophthalmic artery blood flow velocities, however, did not significantly change after the procedure. Successful retinal reattachment with the expected visual improvement was achieved in all patients with this primary surgery. Scleral buckling procedures with encircling elements decrease blood flow velocities in the central retinal artery but leave the ophthalmic artery unaffected. Good anatomic and functional results still can be achieved despite these hemodynamic changes.