Abstract
Purpose :
Elevated intraocular pressure (IOP) has been identified as the leading risk factor for glaucoma. Understanding the factors that alter IOP allows clinicians to formulate more proactive treatments for the disease. Previous studies using tonometry to collect acute IOP data identified a correlation between anesthesia and IOP. The purpose of this study was to incorporate a continuous wireless monitoring system to examine the influence of anesthetics, body temperature, stress, and other experimental factors on IOP.
Methods :
The anterior chamber of the right eye in adult Brown-Norway rats was cannulated and connected to a wireless pressure sensor via a sterile catheter filled with artificial aqueous humor. Experiments were conducted 24 hours post-surgery. In one set of experiments, IOP data were collected with animals anesthetized with either isoflurane or ketamine and body temperature was monitored with and without heat support using a rectal thermometer. In another set of experiments, IOP data were collected before, during, and after placing animal in a small chamber that restricted movement. IOP data were collected every 4 seconds and averaged in 10-30 minute blocks per test condition.
Results :
There was a 54.2% (n=5) reduction in mean IOP during isoflurane induction. After repeating the isoflurane experiments with heat support, there was a 2.6 % (n=5) reduction in mean IOP, which was not significantly different from baseline. Ketamine evoked a 2.0% (n=4) reduction in mean IOP while maintaining body temperature. Experiments with heat support showed a significantly smaller reduction in IOP compared to those without heat support. Mean IOP increased by 24.1% (n=2) when the animal was placed in the chamber. The IOP elevation was not correlated with chamber temperature, which remained nearly constant.
Conclusions :
Our results indicate that isoflurane and ketamine anesthesia do not themselves alter IOP in rats. The anesthetics do though lower body temperature, which can cause IOP to decrease without heat support. Our results also suggest that acute stress increases IOP.
This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.