Purpose: The study was performed in an attempt to evaluate the pattern of optic nerve head blood flow as a response to an increment of intaocular pressure, to determine whether this response varies between individuals and to determine the time course of this response. Methods: Laser Doppler Flowmetry was used to determine the average velocity, the number of moving red blood cells, and the relative optic nerve head capillary blood flow, calculated from the broadening of the spectrum reflected from a spot on the disc illuminated with a 670nm laser beam. These parameters were measured in 11 subjects at spontaneous levels of intraocular pressure (IOP), after a sudden increase of IOP to approximately 40 mmHg for two minutes and after a release of the suction cup for five minutes. The individual time course of the response to IOP elevation, the average time course, the individulal release response, the average release response and the individual amount of regulation capacity were evaluated. Results: All of the 11 subjects studied showed a response to the increment in IOP within one minute. The amount of response, i.e. the increase of relative ONH blood flow as a response to an initial drop varied from one individual to another. The average blood flow at 90 sec after IOP increase was approx. 90 % of relative ONH blood flow measured at spontaneous IOP. The individual variation ranged from 40 to 100%. The average hyperemic response, i.e. after releasing the suction cup was 40 %. The amount of ONH blood flow increase after pressure increase or after pressure release did not correlate with the spontaneous IOP or the amount of the pressure step to reach 40 mmHg. Conclusions: When challenged by elevated IOP, optic nerve circulation responds after an intial drop with continous increase within 60 sec. The time course, the amount of regulatory response and the amount of hyperemic overshoot after pressure release varies from one individual to another.
|Original language||English (US)|
|Journal||Investigative Ophthalmology and Visual Science|
|State||Published - Feb 15 1996|
ASJC Scopus subject areas
- Sensory Systems
- Cellular and Molecular Neuroscience