Anterior chamber measurements on CO2 laser corneal irradiation.

At threshold irradiation (•—0.1 w./cm.) of the rabbit cornea with a carbon dioxide (COi) laser, there was no detectable rise in intraocular pressure and only a slight (1 to 2° C.) rise in aqueous temperature. On suprathreshold COt corneal irradiation, the intraocular pressure rose to a plateau, during irradiation and then gradually fell. There was a concomitant rise in temperature in the anterior chamber caused by heat conduction from the site of corneal irradiation. Further rise in the temperature of the corneal stroma to the critical temperature range for heat shrinkage of collagen causes the cornea to thicken. This thickening of the cornea helps to bring heated aqueous under the irradiated site more closely in apposition to the lens and iris, thus further increasing the temperature of the anterior lens. Lens indentation was observed in fixed eyes only following pulses of sufficient power and duration to raise the temperature near the surface of the anterior lens to a range of at least 60 to 70° C. Increase in aqueous protein occurred only with irradiation over regions of the iris diaphragm.