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R.F. Ramos, W.D. Stamer; Effect of Pulsatile Pressure on Outflow Facility of Human Anterior Segments in Organ Culture . Invest. Ophthalmol. Vis. Sci. 2006;47(13):224.
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The conventional drainage pathway is a pressure–sensitive regulator of outflow facility in vivo. In human eyes, intraocular pressure oscillations associated with each heartbeat average 2.7 mm Hg. The aim of the present study was to determine the effect of long–term pulsatile pressure on outflow facility through the conventional drainage pathway.
Using the anterior segment perfusion model, post–mortem human eyes (n=5) were perfused at a constant rate (2.5 µl/min) until reaching a stable baseline within a physiological range. Intraocular pulses were then introduced to the system using two pumps, a syringe pump and a pulsatile blood pump, in tandem to simulate the magnitude and frequency of intraocular pressure oscillations found in vivo. Intraocular pressure was recorded over time. Viability of the ocular tissues was evaluated using changes in central corneal thickness over the time of perfusion and standard histology post–perfusion.
The introduction of ocular pulsations resulted in an immediate decrease (within 24 hours) in outflow facility in all human anterior segments tested. A new baseline outflow facility was established within 70 hours, decreasing on average by 28 ± 12% of the original baseline.
Results suggest that cyclic intraocular oscillations in pressure stimulate a contraction of trabecular meshwork tissues that cause a decrease in outflow facility. The absence of ciliary muscle tone to counterbalance a TM response in these preparations may explain the increased intra–chamber pressure in response to pressure pulsations.
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