Determination of the facility of aqueous humor outflow in the dog, comparing in vivo and in vitro tonographic and constant pressure perfusion techniques.

The gross facility of aqueous humor outflow (C) was estimated in the normal in vivo and in vitro dog eye, using tonography and constant pressure perfusion. Tonographic C value for 36 normal eyes, with the dog anesthetized with ketamine hydrochloride and acetylpromazine maleate, was 0.21 (+/- 0.14, SD); the mean tonographic value in 35 eyes with the patient anesthetized with sodium pentobarbital was 0.15 (+/- 0.09). Constant pressure perfusion of the in vivo normal dog eyes at 20 mm of Hg intraocular pressure yielded a mean C value of 0.13 (+/- 0.07) and at 30 mm of Hg 0.18 (+/- 0.13). As intraocular pressure increased from 10 to 50 mm of Hg, the rate of outflow, as determined by constant pressure perfusion, increased. The C values from in vitro constant pressure perfusion were greater than those in the in vivo eyes and deceased in most eyes as intraocular pressure was increased as compared with the in vivo preparation.