Rv. Searles et al., COMPARISON OF ANTERIOR-CHAMBER INFUSATES ON THE INTRAOCULAR-PRESSURE OF INTACT RAT EYES, General pharmacology, 27(6), 1996, pp. 1073-1076
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.