Intraocular pressure and pulsatile ocular blood flow after retrobulbar andperibulbar anaesthesia

Aims-This study investigated the effect of peribulbar and retrobulbar local anaesthesia on intraocular pressure (IOP) and pulsatile ocular blood flow (POBF), as such anaesthetic techniques may adversely affect these parameter s. Methods-20 eyes of 20 patients who were to undergo phacoemulsification cata ract surgery were prospectively randomised to receive peribulbar or retrobu lbar anaesthesia. The OBF tonometer (OBF Labs, Wiltshire, UK) was used to s imultaneously measure IOP and POBF before anaesthesia and 1 minute and 10 m inutes after anaesthesia. Between group comparisons of age, baseline IOP, a nd baseline POBF were performed using the non-parametric Mann-Whitney test. Within group comparisons of IOP and POBF measured preanaesthesia and post- anaesthesia were performed using the non-parametric Wilcoxon signed ranks t est for both groups. Results-There was no statistically significant IOP increase post-anaesthesi a in either group. In the group receiving peribulbar anaesthesia, there was a significant reduction in POBF initially post-anaesthesia which recovered after 10 minutes. In the group receiving retrobulbar anaesthesia, there wa s a persistent statistically significant reduction in POBF. Conclusions-Retrobulbar and peribulbar injections have little effect on IOP . Ocular compression is not needed for IOP reduction when using local anaes thesia for cataract surgery. Conversely, POBF falls, at least for a short t ime, when anaesthesia for ophthalmic surgery is administered via a retrobul bar route or a peribulbar route. This reduction may be mediated by pharmaco logically altered orbital vascular tone. It may be safer to use other anaes thetic techniques in patients with ocular vascular compromise.