The Effect of Antibiotics in the Irrigation Solution on Corneal Endothelial Function

The practice of adding antibiotics to anterior chamber-irrigating solutions as a prophylaxis for endophthalmitis has been used recently.To evaluate corneal endothelial toxicity of different concentrations of antibiotics in irrigating solutions, rabbit corneas were mounted in the in-vitro dual-cham-bered specular microscope and the endothelium was perfused with glu-tathione-bicarbonate Ringer solution (GBR)containing antibiotics such as ofloxacin, vancomycin or cephapirin.Mate corneas were perfused with GBR alone and used as control.Corneal thickness was measured every 15 minutes throughout the perfusion period and corneal swelling rates were calculated. Swelling rates of corneas perfused with 2 /ml or 5 /ml ofloxacin, 60 microgram/ml or1 0 /ml vancomycin, and 10 /ml or 20 /ml cephapirin was not significantly different from that of control (p>0.05).The corneas perfused with 20 /ml cephapirin deswelled probably due to high osmolarity of it.Perfusion with 10 /ml vancomycin plus 5 /ml ofloxacin did not show corneal swelling compared to control (p>0.05).This study demonstrates that the above concentra-tions of antibiotics in irrigating solutions do not affect endothelial function of the rabbit cornea.

Effect of Ascorbic Acid on Corneal Endothelial Function

It has been reported that ascorbic acid[AA]appears to be actively taken up by the corneal endothelium and protect the endothelium against harmful effects of the oxidative reactions. To investigate the effect of ascorbic acidon the corneal endothelial function, rabbit`s corneas were mounted in the in vitro specular microscope. Corneal endothelium was perfused with ascorbic acid, then switched to AA plus ouabain solution, and vice versa. Also, phloretin was perfused onto the endothelium with AA and ouabain. Andcorneal endothelium was perfused with GBR or AA solution followed by perfusion with ouabain. Corneal thickness was measured during the perfusion and the corneal swelling rate calculated. Corneal endothelial permeability was also measured after perfusion of ascorbic acid. Perfusion with AA showed no corneal swelling, but swelling rate was even lower than GBR control. Corneal endothelial permeability did not change upon AA perfusion. In corneas preperfused with ouabain, AA added to ouabain solution decreased corneal swelling rates induced by ouabain solution[19.9 vs. 40.5 micrometer/hr]. The corneas preperfused with AA also showed decreased swelling rates with subsequent perfusion of ouabain added to AA solution[21.7 vs.28.6 micrometer/ hr]. Phloretin inhibited the effect of AA.However, when ouabain was removed, the corneal swelling plateaued but did not return to baseline thickness in both AA and GBR perfusion.The results of this study showed that AA can increase corneal endothelial pump function and reduce corneal swelling caused by ouabain.

The Changes of Ultrastructure and Function of the Corneal Endothelial Cell Caused by Benzalkonium Chloride

The purpose of this study was to evaluate alterations in corneal endothelial cell function and ultrastructure caused by benzalkonium chloride (BAC). Sixteen albino rabbits (32 eyes)were used for this study. One cornea of each matched pair was assigned to experimental group and the other cornea to control group. The experimental groups were divided into 4 groups, of which corneal endothelium were perfused with 0.01%, 0.001%, 0.0002%, and 0.0001% BAC. After paired rabbit corneas were isolated and mounted in the in vitro dual-chambered specular microscope, experimental corneas of each matched pair were perfused with different concentrations of BAC. Control corneas were perfused with glutathione-bicarbonate-Ringer solution(GBR). Corneal thickness was measured every 15 minutes throughout the perfusion period.Swelling rates were calculated by linear regression analysis, and compared to swelling rate of each paired mate perfused with GBR alone. At the end of perfusion,the corneas were fixed in 2.5%glutaraldehyde solution for transmission electron microscopy(TEM). Swelling rates of rabbit corneas perfused with BAC, 0.0001% did not differ significantly from control corneas (p>0.05). But, 0.0002%, 0.001%, and 0.01% BAC differed significantly from control corneas (p<0.05). BAC, 0.0001% showed normal corneal endothelial findings, but 0.0002% and 0.001% BAC showed reversible endothelial cellular injury. BAC, 0.01% showed irreversible endothelial cellular injury such as loss of nuclear membrane and disruption of cellular organelles. The results of this study indicate that long-term use of topical eye solutions containing BAC might induce corneal endothelial damage, especially in the absence of epithelial barrier such as corneal ulcer.