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Canadian Journal of Anesthesia, Vol 41, 802-806, Copyright © 1994 by Canadian Anesthesiologists' Society

ARTICLES

The electroretinogram during orbital compression following intraorbital regional block for cataract surgery

RG Loken, SG Coupland and MC Deschenes
Department of Anaesthesia, Foothills Hospital, Calgary, Alberta, Canada.

The electroretinogram (ERG) is a transient biopotential that reflects the electrical response of the distal retina to photostimulation. Disturbances in retinal circulation produce characteristic abnormalities in the ERG wave form. The objective of this study was to investigate the changes in the ERG produced by combined retrobulbar and peribulbar injections of a large volume (8 ml) of local anaesthetic, followed by ocular compression. Electroretinogram recordings were obtained from skin electrodes placed on the infero orbital ridge in response to stroboscopic flash stimulation in 34 adult patients undergoing cataract surgery: (a) prior to regional anaesthesia (baseline condition); (b) within one minute after regional anaesthesia of the orbit (block condition); (c) after ten minutes of orbital compression with a Honan's device at 30 mmHg. (compression condition); (d) and five minutes after removal of orbital compression (recovery condition). The ERG implicit times of both a- and b-wave increased (P < 0.001) after anaesthetic block. The amplitude of the a- and b-waves also decreased (P < 0.001) immediately following anaesthetic block and continued to decrease following application of the compression device (P < 0.01). Following removal of ocular compression the amplitude of the b-wave increased (P < 0.01). Only the a-wave implicit time (P < 0.005) decreased with release of ocular compression. These findings are compatible with the ERG changes of transient retinal ischaemia produced by ocular compression.


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Y Akar, K C Apaydin, and A Ozel
Acute orbital effects of retrobulbar injection on optic nerve head topography
Br. J. Ophthalmol., December 1, 2004; 88(12): 1573 - 1576.
[Abstract] [Full Text] [PDF]


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Copyright © 1994 by the Canadian Anesthesiologists' Society.