Rabbit corneas have been exposed to radiation from a CO2 laser emitting a spatially smooth beam. Energy densities of 1.2 Joules (J)/sq cm, 0.77 J/sq cm, and 0.55 J/sq cm were found to cause minimal damage to the cornea at exposure times of 55, 10, and 3.5 msec. At these levels damage was confined to the corneal epithelium and was manifested by a flat, white area of edema which disappeared within 24 hours. A theoretical heat-flow model was constructed to predict temperature rise as a function of depth and exposure time. A comparison of the model with experimental data suggests that a threshold lesion may be caused at a temperature rise of 35 C.
Peabody RR, Zweng HC, Rose HW, Peppers NA, Vassiliadis A. Threshold Damage From CO2 Lasers. Arch Ophthalmol. 1969;82(1):105-107. doi:10.1001/archopht.1969.00990020107025