Stress raises intraocular pressure in rabbits

Purpose. To test whether encagement and volume load as stressors influence the intraocular pressure in rabbits. Method. Rabbits were encaged for an hour in a horizontally-plastic tube with an internal diameter of 13.2 cm and a length of 33.2cm. After the encagement, rabbits received a rapid intraveonus drip infusion of 5% glucose solution, 20 ml per kilogram of body weight, for 5-6 minutes. All experiments were performed at the same time of day. Results. The intraocular pressure after encagement (11.2±3.0mmHg as a mean and standard deviation) was significantly higher compared with that of control rabbits without encagement (9.2±1.0mmHg, Student t-test,p=0.046). This differnce became signifficantly larger when volume load was exerted on both groups of rabbits (p=0.0007). Serum levels of cortisol, adrenaline, and nordrenaline were significantly elevated afte encagement (n=6, p=0.0002, p=0.027, p=0.030, respectively). Venous pressure of the ear tended to increase in rabbits after encagement (15.8±3.1mmHg) compared with that of control rabbits (8.5±2.3mmHg,p=0.11), and the difference became significant when volume load was placed on each group of rabbits (p=0.021). Conclusions.Encagement, especially in combination with volume losd, increased the intraocular pressure in rabbits. The elevation of peripheral venous pressure caused by an increase in serum catecholamines would underlie the elevation of intraocular pressure proh-ably through the increased outflow resistance.

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