TY - JOUR
T1 - Autoregulation of human optic nerve head circulation in response to increased intraocular pressure
AU - Pillunat, Lutz E.
AU - Anderson, Douglas R.
AU - Knighton, Robert W.
AU - Joos, Karen M.
AU - Feuer, William J.
N1 - Funding Information:
Supported in part by a grant from The Glaucoma Research Foundation, San Francisco, California ; in part by the National Research Service Award T32 EY-07021 and by Clinical Vision Research Development Award R21 EY-10900, awarded by the National Eye Institute, Bethesda, Maryland; in part by Humphrey Instruments, Inc., San Leandro, California, a company of the Carl Zeiss Group; and in part by a grant of the Deutsche Forschungsgemeinschaft Pi 181}3-1, Bonn, Germany.
PY - 1997/5
Y1 - 1997/5
N2 - The following experiments were undertaken to determine if blood flow is maintained by autoregulation in the human optic nerve head when circulation is challenged by elevated intraocular pressure, and to determine if the presence or absence of autoregulation is universal. Laser Doppler flowmetry was used to determine the average velocity, the number of moving erythrocytes, and the volume of flow in the capillary bed of the optic disc. These parameters were measured in 10 subjects at spontaneous levels of intraocular pressure (IOP), and at pressures artificially elevated to 25, 35, 45 and 55 mm Hg with a scleral suction cup. Four subjects (two who showed autoregulation and two who did not) were studied on six additional occasions to determine consistency of the findings. In these same four subjects a second location on the disc was also measured on six occasions to determine if the IOP-effect on blood flow varied by location. Of the 10 subjects initially studied, seven maintained the baseline level of blood flow over the lower part of the range of elevated intraocular pressure (evidence of autoregulation), but showed a decline in flow by the time IOP reached 45 or 55 mm Hg. Two subjects showed a linear decline in blood flow beginning with the smallest increment of elevation of IOP (no autoregulation), and one showed an uninterpretable result. The two individuals who showed the linear decline and two of those who showed efficient autoregulation were remeasured, and each showed consistently the same pattern as before when restudied on six different occasions each. However, at a different location on their discs, autoregulation was manifest in all of these four individuals. When challenged by elevated IOP, the optic nerve head typically maintains a steady-blood flow over a range of IOP, but fails to maintain the same flow by the time IOP reaches 45 or 55 mm Hg. Some disc locations, at least in some individuals, do not show this autoregulation, but exhibit a decline in blood flow linearly related to IOP, even with the modest elevation of IOP.
AB - The following experiments were undertaken to determine if blood flow is maintained by autoregulation in the human optic nerve head when circulation is challenged by elevated intraocular pressure, and to determine if the presence or absence of autoregulation is universal. Laser Doppler flowmetry was used to determine the average velocity, the number of moving erythrocytes, and the volume of flow in the capillary bed of the optic disc. These parameters were measured in 10 subjects at spontaneous levels of intraocular pressure (IOP), and at pressures artificially elevated to 25, 35, 45 and 55 mm Hg with a scleral suction cup. Four subjects (two who showed autoregulation and two who did not) were studied on six additional occasions to determine consistency of the findings. In these same four subjects a second location on the disc was also measured on six occasions to determine if the IOP-effect on blood flow varied by location. Of the 10 subjects initially studied, seven maintained the baseline level of blood flow over the lower part of the range of elevated intraocular pressure (evidence of autoregulation), but showed a decline in flow by the time IOP reached 45 or 55 mm Hg. Two subjects showed a linear decline in blood flow beginning with the smallest increment of elevation of IOP (no autoregulation), and one showed an uninterpretable result. The two individuals who showed the linear decline and two of those who showed efficient autoregulation were remeasured, and each showed consistently the same pattern as before when restudied on six different occasions each. However, at a different location on their discs, autoregulation was manifest in all of these four individuals. When challenged by elevated IOP, the optic nerve head typically maintains a steady-blood flow over a range of IOP, but fails to maintain the same flow by the time IOP reaches 45 or 55 mm Hg. Some disc locations, at least in some individuals, do not show this autoregulation, but exhibit a decline in blood flow linearly related to IOP, even with the modest elevation of IOP.
KW - Autoregulation
KW - Blood flow
KW - Intraocular pressure
KW - Laser Doppler Flowmetry (LDF)
KW - Optic nerve head
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U2 - 10.1006/exer.1996.0263
DO - 10.1006/exer.1996.0263
M3 - Article
C2 - 9245904
AN - SCOPUS:0031149796
VL - 64
SP - 737
EP - 744
JO - Experimental Eye Research
JF - Experimental Eye Research
SN - 0014-4835
IS - 5
ER -