Abstract
Purpose :
Episcleral venous pressure (EVP) is important for steady state intraocular pressure (IOP), as it has to be overcome by aqueous humor in order to leave the eye. It was long assumed to be constant, but recent evidence suggests neuronal control, with a vascular tone through the innervation present. The superior salivatory nucleus in the brainstem could be identified to elicit increases in EVP during electrical stimulation. In the present study the effect of topical anesthesia on the stimulation effect was investigated.
Methods :
8 Spraque Dawley rats were anesthetized, artificially ventilated with CO2 monitoring and continuous blood pressure monitoring. Intraocular pressure was measured continuously through a cannula in the vitreous body. Episcleral venous pressure was measured by direct cannulation of an episcleral vein via a custom made glass pipette connected to a servonull micropressure system.
Results :
Electrical stimulation of the superior salivatory nucleus (10µA, 200 pulses of 1ms duration) increased EVP from 8,51 ± 1,82 mmHg to 10,97 ± 1,93 mmHg (p<0,05). After topical application of topical lidocaine EVP increased from 7,42 ± 1,59 mmHg to 9,77 ± 1,65 mmHg (p<0,05). The EVP response to stimulation before and after lidocaine application was not statistically significantly different (2,45 ± 0,5 vs 2,35 ± 0,49 mmHg, p = 0,69), while the decrease in baseline EVP was (8,51 vs. 7,42 mmHg, p <0,05)
Conclusions :
The present data suggest that distinct neuronal mechanisms controlling the episcleral circulation of rats exist. This is in keeping with previous reports of two distinct arterio-venous anastomoses, one in the limbal circulation and one in the conjunctival/episcleral circulation.
This is a 2021 ARVO Annual Meeting abstract.