EFFECT OF CARBOGEN, OXYGEN AND INTRAOCULAR-PRESSURE ON HEIDELBERG RETINA FLOWMETER PARAMETER FLOW MEASURED AT THE PAPILLA

The aim of the study was to evaluate whether the Heidelberg retina flo wmeter (HRF), a new device for retinal and anterior optic nerve blood flow assessment, can gauge, at least semiquantitatively, a known effec t such as an increase in optic nerve blood flow by hypercapnia or a de crease in optic nerve blood flow by hyperoxia or high intraocular pres sure (IOP). Measurements with the HRF were obtained at the papilla of three groups of 5 young healthy subjects (1) at baseline and after bre athing 5% carbogen, (2) at baseline and after breathing 100% oxygen an d (3) at baseline and after increasing IOP to 20 and 50 mm Hg. The cha nges in the value of the HRF parameter 'flow' were analyzed by means o f a paired Student's t test. Breathing 100% oxygen for 7 min resulted in a statistically significant decrease of 34.7+/-2.5% (mean +/- SEM) in HR parameter 'flow' (p<0.01) at the papilla. Breathing 5% carbogen for 7 min resulted in a statistically significant increase of 18.3+/-2 .6% in HRF parameter 'flow' (p = 0.024). Increasing IOP to 20 mm Hg di d not result in a statistically significant change in HRF parameter 'f low' (-9.6+/-74%, p = 0.13). Increasing IOP from 20 to 50 mm Hg, howev er resulted in a statistically significant decrease of 40.1+/-6.6% in HRF parameter 'flow' (p = 0.003). With the applied stimuli, the HRF pa rameter 'flow' changed in the expected direction, i.e. an increase wit h hypercapnia and a decrease with hyperoxia or high IOP. The simplicit y of use of the HRF instrument suggests that it might be well suited f or a non-invasive, at least semiquantitative, assessment of changes in blood flow at the papilla.