COMPARISON OF ANTERIOR-CHAMBER INFUSATES ON THE INTRAOCULAR-PRESSURE OF INTACT RAT EYES

1. Infusions of balanced salt solutions (BSS) into the eye often cause a delayed, gradual increase in intraocular pressure or outflow facili ty, known as the ''washout'' effect. The reason(s) is occult, especial ly at low input rates when drainage mechanisms are not overloaded by e xcessive volume input. However, direct, quantitative comparisons of BS Ss used in ocular research have been reported infrequently. 2. We comp ared the effects of three BSSs on intraocular pressure and the estimat ed resistance to drainage after a 1-hr, low-volume infusion into the a nterior chambers of the eyes of anesthetized rats. 3. The BSSs tested raised intraocular pressure (P<0.05) after a 20-40-min delay, and the highest IOPs occurred at 1 hr. Recovery of intraocular pressure to bas eline only occurred with one BSS (Dulbecco). 4. Fitting the ascending and descending portions of the mean pressure curl es to an exponential revealed differences among the infusates. The Dulbecco solution resul ted in minimal changes in time constant, gain, and offset during the a scending and descending periods. 5. The data obtained show that differ ent BSSs yield pressure curves that appear grossly similar, even thoug h there were large differences in composition and osmolality. However, the underlying changes in ocular dynamics were not identical. Thus, i t may be prudent to test more than one solvent to study ''washout,'' o r to deliver drugs directly into the anterior chamber.