Characterization of the oculocardiac reflex during compression of the globe in Beagle dogs and rabbits

Abstract

This investigation characterizes the occurrence of oculocardiac reflex (OCR) in conscious rabbits and dogs by observing the effect of an ocular compression stimulus on heart rate (HR). Thirty-four clinically healthy adult rabbits and 15 clinically healthy adult Beagle dogs were studied. An electrocardiogram was used to record the heart rhythm and HR continuously. Digital pressure was exerted over the eyelid on right eye, left eye and both eyes together for 1 min, with one-minute intervals between each compression. Variations in HR were observed in each minute by counting complexes on the electrocardiographs. There were no differences in HR between stages without ocular compressions both in dogs and in rabbits. HR reduction caused by ocular compression was statistically significant in rabbits only when both eyes were compressed in contrast with all stages without compression. In dogs, a statistically significant reduction in HR was seen during compression of just the right eye or the left eye compared with the baseline HR, and when both the right and left eyes were compressed together compared with baseline or after compression of the right eye. In dogs, compression of individual eyes produced a change similar to that seen during compression of both eyes. This study shows that OCR can occur during experimental ocular compression in conscious rabbits and Beagle dogs and characterizes the reduction in HR. Knowledge of this physiological response is important for veterinary anesthetists and ophthalmologists during ophthalmic surgery or eye manipulations.