Correlation of tonography and constant pressure perfusion measurements of outflow facility in the rabbit

The values of aqueous outflow facility, determined using tonography and constant pressure perfusion, were compared in the New Zealand white rabbit. Four-minute indentation tonography was followed by multi-level constant pressure perfusion lasting 60 minutes in one randomly chosen eye of each animal. Mean outflow facility was 0.26 +/- 0.07 microliter/(min) (mmHg) using tonography and 0.26 +/- 0.6 microliter/(min) (mmHg) using constant pressure perfusion. These values are similar (p greater than 0.6) and show significant correlation (r = 0.914, p less than 0.001). Constant pressure perfusion was associated with a time-dependent facility increase, and with increased flow and stable resistance at higher infusion pressures. These results suggest that tonography may represent a repeatable, reproducible, and valid noninvasive technique to monitor outflow facility in this animal. This may be important in the evaluation of medications which alter wound healing after glaucoma filter surgery.