Endophotocoagulation in vitrectomy with a carbon dioxide laser.

A continuous-wave carbon dioxide laser operating at a wavelength of 10.6 microns has been applied transvitreally by means of a miniature articulating arm and intraocular probe to produce chorioretinal lesions in albino white rabbit eyes. The advantages of using a carbon dioxide laser are its lack of pigment dependence, its ability to act both as a photocoagulator and as a phototransector, and its ability to deposit its energy in a well-defined area without adverse effect on neighboring ocular tissue. The main disadvantage of the carbon dioxide laser in vitreoretinal surgery is that in a fluid medium, such as the vitreous, the laser tip must be placed in direct physical contact with the target tissue to obtain a reaction.

Syneresis of vitreous by carbon dioxide laser radiation.

In carbon dioxide laser surgery of the vitreous a process of vaporization has been advocated. In this report syneresis, a thermal liquefaction of gel, is shown to be over ten times more efficient on an energy basis than vaporization. Syneresis of vitreous is experimentally shown to be a first-order kinetic process with an activation energy of 41 +/- 0.5 kilocalories per mole. A theory of laser surgery in which this figure is used agrees closely with results from laser experiments on human eye-bank vitreous. The syneresis of vitreous by carbon dioxide laser radiation could lead to a more delicate form of ocular microsurgery, and application to other biological systems may be possible.