Freshly isolated stroma-endothelial preparations were perfused with a glucose, adenosine and glutathione-supplemented Ringer solution at 37 degrees C at a hydrostatic pressure of 20 cm H2O. The composition (tCO2, pH, Ca2+ and osmolality) of the stromal-side bathing solution was analyzed during a 90-min equilibration period during which this solution was covered or deliberately left open to the atmosphere. If exposed to the atmosphere, even for a few minutes, substantial changes in pH, osmolality and ionized calcium occurred such that, when silicone oil was subsequently applied to the stromal surface, significant increases in both the rate and amplitude of deturgescence were observed. The rates and amplitude were proportional to the corneal thickness prior to silicone oil application. The results further indicate that the physicochemical state of the stroma is an important determinant in the corneal deturgescence mechanism.