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Y. Liang, L. Wang, G. Cull, C. F. Burgoyne, G. A. Cioffi; Time-Domain Analysis of Dynamic Blood Flow Autoregulation in Optic Nerve of Rhesus Monkeys. Invest. Ophthalmol. Vis. Sci. 2009;50(13):5854.
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© ARVO (1962-2015); The Authors (2016-present)
To develop a novel technique to assess the dynamic capacity of blood flow (BF) autoregulation in the optic nerve head (ONH) in normal primate eyes.
In both eyes of 4 monkeys under pentobarbital anesthesia, two needles were inserted into the anterior chamber - one was connected to a saline reservoir to manometrically set IOP and the other to a pressure transducer. Mean arterial BP was maintained between 80~90 mmHg and monitored continuously. With a Laser Speckle Flowgraphy, blood flow (BF) in the ONH was recorded at IOP 10 mmHg continuously for 10 sec, and followed by another 2 min when the IOP was raised to 40 mmHg in 2 sec. Time domain analysis of the BF response to the IOP change was performed offline to extract parameters to characterize the dynamic BF autoregulation, including baseline BF, maximal BF change (BFmax), time to reach the maximal change (Tr), and the BF recovering slope at 20 seconds (K20) after the BF reached the maximal change; Fig 1 illustrates the definitions of the parameters.
After the reservoir was raised to 40 mmHg, the IOP increased rapidly during the first 7~9 sec, then slowed down. It took 10~15 sec in total to equilibrate to the pressure of the reservoir. The BF decreased sharply immediately after the IOP started to increase and reached maximum in 6.9±1.5 sec (Tr , mean±SD). When the BF started returning towards baseline, it recovered quickly in the first 15~30 seconds and then slowed down. The average recovering slope (K20) is 0.053±0.012 per sec (arbitrary unit) for the first 20 seconds after the maximal change of BF. The maximal BF change (BFmax) was -19.9%±5.5% of all eyes when IOP was increased from 10 mmHg to 40 mmHg. The dynamic parameters Tr (P=0.27), K20 (P=0.47) and BFmax (P=1.0) had no significant difference between the left and right eyes.
During the initial 10-20 seconds after IOP change, the BF in the ONH exhibited dynamical adjustments. Characterization of the adjustment with the parameters introduced above may represent a pattern of dynamic autoregulation in the ONN. Studies designed to detect the autoregulation changes in the ONH of experimental glaucoma, is currently underway in our laboratory.
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