Corneal endothelial injury thresholds for exposures to 1.54 micro m radiation

The endothelial injury threshold was determined in rabbit for an 11-s exposure to 1.54 micro m radiation from an Erbium fiber laser. The beam was Gaussian with a 1/e diameter of 7 mm. Cell damage was detected with a wet staining technique. The threshold dose for these conditions is 4.4 x 10(5) J m(-2) (44 J cm) and is only 9% greater than the threshold for epithelial damage for the same exposure conditions. Exposures just above the threshold caused substantial endothelial damage, including loss of cells. The calculated endothelial temperature increase at the threshold is similar to that calculated for the epithelium at its injury threshold for the same exposure conditions. The results suggest that endothelial damage can be correlated with a critical temperature damage model with a critical temperature increase near 40 degrees C. The results also suggest that if a person were to receive an exposure only slightly above the epithelial injury threshold from a beam having a diameter of 7 mm (which is the diameter of the exit pupil of 7 x 50 binoculars) he or she would risk sustaining substantial endothelial damage.