Читать книгу Essentials of Veterinary Ophthalmology - Kirk N. Gelatt - Страница 104

The oculocardiac reflex can cause reflexive slowing of the heart and can be stimulated by pressure on the globe, tension on the EOMs or iris, or increased intraorbital pressure caused by injection, hemorrhage, or a foreign body. The most common effect of the reflex is bradycardia, but other clinically significant effects are cardiac arrest and ventricular fibrillation. The oculocardiac reflex has been reported in humans, dogs, cats, horses, rabbits, mice, and a cockatiel. The afferent arc of the oculocardiac reflex begins with the long and short ciliary nerves to the ciliary ganglion. The ophthalmic division of the trigeminal nerve (CN V) continues to the trigeminal ganglion to its sensory nucleus. The afferent arc continues along short internuncial fibers in the reticular formation to connect with the efferent pathway in the motor nucleus of the vagus nerve (CN X) to the myocardium. Sensory stimulation of the eye and orbital areas results in stimulation of the vagal nucleus in the brain stem, thus causing a reflexive slowing of the heart. Conscious, healthy rabbits and dogs do not show clinically significant decreases in heart rate with globe compression of 1 min. Endotracheal intubation can cause vagal stimulation as well, resulting in similar reflexive cardiac alterations. In the dog, as the IOP increases, the heart rate may also increase, thus indicating the possibility of an intraocular‐sympathetic‐cardiac reflex as well as a trigeminovagal reflex.