[Changes in uveal and retinal hemodynamics caused by retrobulbar anesthesia using various injection volumes]

In 20 patients, retrobulbar injections of 2 or 5 ml local anesthetic (bupivacaine-lidocaine mixture with hyaluronidase) were given preoperatively. Directly after the 5-ml injection, the systolic retinal and ciliary perfusion pressures (measured by means of oculo-oscillo-dynamography according to Ulrich) were reduced by an average of 5.6 mmHg (p less than 0.001) in comparison with the untreated fellow eyes. The ocular pulsation volume (PVoc) was reduced by 39%. Fifteen minutes after the 5-ml injection, the perfusion pressures and PVoc were reduced even slightly more. The intraocular pressure (Pio) was increased by an average of 3.2 mmHg directly after the 5-ml injection, whereas after 15 min the Pio had reassumed its preinjection level. After the 2-ml injection, the PVoc was reduced by the same amount as found after the 5-ml injection. However, there was no significant change in perfusion pressures or Pio after the 2-ml injection. The findings observed during retrobulbar anesthesia may be interpreted as an inhibitory effect on ocular hemodynamics, which increases at higher injection volumes. This effect cannot be accounted for by adrenaline--which was not employed--and can at best only partially be accounted for by the changes in Pio.