EFFECTS OF IRRIGATION SOLUTIONS ON CORNEAL ENDOTHELIAL FUNCTION

Rabbit corneas were perfused in vitro with an irrigation solution for 90 minutes. This was followed by 6 hours of perfusion with tissue cult ure medium TC199 during which endothelial function was assessed by mon itoring rates of swelling during a period of perfusion in the absence of bicarbonate ions, and subsequent rates of thinning when bicarbonate ions were restored to the perfusate. Corneal thickness (measured with an ultrasonic pachymeter) immediately following excision was 401 I-lm (SD 19, n = 23). During the 90 minute perfusion at 35 degrees C, corn eas exposed to balanced salt solution (BSS), Hartmann's solution or 0. 9% NaCl (all initially at room temperature) swelled, respectively, at 14 (SD 2.3, n = 4), 11 (SD 2.6, n = 4), and 70 (SD 4.3, n = 4) mu m/h. Cold Hartmann's solution (initially at 4 degrees C) caused corneas to swell at 9 (SD 2.3, n = 4) mu m/h. On the other hand, corneas perfuse d with BSS Plus thinned at 9 (SD 3.4, n = 4) mu m/h and TC199 with Ear le's salts had little effect on thickness. Rates of swelling and thinn ing during the following assessment perfusion showed no apparent effec ts of prior exposure to any of the irrigation solutions on the barrier properties or pump function of the endothelium. Despite this, the inc reased thickness of corneas exposed initially to BSS, cold Hartmann's solution, or 0.9% NaCl was not fully reversed, even by the end of the 6 hour assessment perfusion. In contrast, the swelling observed in cor neas exposed to Hartmann's solution at room temperature was reversed a nd these corneas had returned to their normal thickness by the end of the assessment period. All corneas, even those exposed to 0.9% NaCl, h ad an intact endothelial mosaic with no evidence of damage or cell los s, although morphological differences in cell shape and the appearance of cell borders were evident compared with freshly isolated cornea.