Objective: To characterize the mechanism by which air bubbles damage t
he corneal endothelium during phacoemulsification. Materials and Metho
ds: A series of experiments was conducted to expose the corneal endoth
elium of New Zealand white rabbit and human eyes that were obtained fr
om an eye bank to air under different conditions. Phacoemulsification
at different power settings and irrigation with and without the introd
uction of air into the anterior chamber were performed. Corneal endoth
elial perfusion experiments were conducted with air bubbles that were
introduced into the perfusion chamber for 2 seconds to 1 hour. Air was
also injected into the anterior chambers of anesthetized rabbits for
2 minutes to 3 hours. Corneas were stained with nitrobenzoxadiazole-ph
allacidin and examined with fluorescence microscopy. Selected corneas
were also examined with scanning and transmission electron microscopy.
Results: Intracameral air bubbles during phacoemulsification, irrigat
ion, and perfusion studies resulted in a severe injury to the corneal
endothelium in as little as 20 seconds. Intracameral air bubbles in a
living rabbit resulted in a slower injury that was morphologically dif
ferent from the more rapid injury. Conclusions: Air bubbles in intraoc
ular fluids with a high surface tension can cause a ring-shaped patter
n of damage to the corneal endothelium. The mechanism that caused this
pattern of damage appears to be a surface tension phenomenon.