Purpose:
To investigate the oxygen supply in the anterior segment ofthe eyes of anesthetized rabbits.
Methods:
Mean arterial pressure (MAP) and intraocular pressure (IOP)by direct cannulation of the central ear artery and the vitreousrespectively. Laser Doppler flowmetry was used to measure ciliaryblood flow (n=5) while oxygen tension was measured with twoindependent fluorescent probes at the endothelial side of thecornea and the anterior surface of the lens. To change oxygengradients the cornea was exposed to nitrogen or oxygen contentof the breathing air was lowered (Table 1). The third perturbationwas a decrease in ciliary blood flow in response to topicalapplication of brimonidine 0,1% (Table 2). CarBF was measuredwith a bidirectional ultrasonic probe on the ipsilateral carotidartery.
Results:
Table 1. Table 2.
Conclusions:
Substantial changes of the oxygen gradients in response to allperturbations were observed (see tables). As reported previouslythe cornea is an important source of oxygen in the anteriorchamber. In the present study we found that this is the case,even at the level of the anterior lens surface. However, changingciliary blood flow also impacts the oxygen levels at the cornea.The equilibrium of oxygen gradients in the anterior segmentseems to be very sensitive to local and systemic perturbations.
Keywords: anterior segment • blood supply