A 3-dimensional ultrasound C-scan imaging technique for optic nerve measurements.

PURPOSE: To evaluate the use of 3-dimensional ultrasound C-scan imaging for optic nerve diameter measurements. DESIGN: Prospective observational case series. PARTICIPANTS: Thirty-eight normal eyes of 32 healthy adults. METHODS: Coronal C-scans of 38 normal optic nerves were imaged 3 mm behind the globe. MAIN OUTCOME MEASURES: Optic nerve sheath diameter (ONSD) and optic nerve diameter (OND). RESULTS: Mean ONSD was 4.8 mm (range: 3.9-5.9; SD 0.6), whereas mean optic OND was 1.9 mm (range: 1.8-2.1; SD 0.1). Mean ONSDs were 4.9 mm (male), 4.5 mm (female), 5.0 mm (subjects younger than 50 years), and 4.6 mm (subjects 50 and older). CONCLUSION: Coronal C-scans generated from 3-dimensional ultrasound can be used to measure the optic nerve diameters in adult eyes.

Retinal blood flow in the normal human eye using the canon laser blood flowmeter.

PURPOSE: To establish a retinal blood flow database in normal human eyes using the Canon Laser Blood Flowmeter (CLBF). METHOD: Fourteen healthy subjects (7 males, 7 females) between the ages of 24 and 33 underwent birectional laser Doppler velocimetry (BLDV) in one eye using the CLBF. Measurements consisting of blood vessel diameter (D) in micrometers, velocity (V) in millimeters per second, and flow (F) in microliters per minute were recorded at sites along the major retinal veins. Four to six veins were measured in each eye. Total volumetric blood flow was calculated as the sum of the venous flow rates in the major veins. RESULTS: Total retinal blood flow could be reliably determined on 5 of the subjects (1 male, 4 females). Venous blood vessel diameter ranged from 84 to 177 microm. The correlations between D and F, as well as D and V were found to be significant. Specifically, the correlation coefficient between D and F was 0.885 (p < or = 0.001), while the log-log regression coefficient was 3.35 +/- 0.23 (p < or = 0.001). The correlation coefficient between D and V was 0.694 (p < or = 0.001), while the log-log regression coefficient was 1.43 +/- 0.27 (p < or = 0.001). Total venous blood flow showed a mean of 64.9 +/- (SD) 12.8 microl/min (range: 50.9-80.6 microl/min). Venous blood flow averaged 44.1 +/- 4.5 microl/min temporally and 20.8 +/- 9.2 microl/min nasally, showing a temporal retinal blood flow approximately twice that of the nasal retina (p < 0.001). On the other hand, venous blood flow averaged 30.6 +/- 9.8 microl/min superiorly and 34.3 +/- 8.0 microl/min inferiorly. These values showed no statistical difference. CONCLUSION: The average total retinal blood flow in 5 healthy subjects using the CLBF was 64.9 +/- 12.8 microl/min. Venous blood flow at the temporal retina was about twice that of the nasal retina, whereas flow at the superior and inferior retina showed no statistical difference. Our findings are comparable with studies done using a different BLDV system.