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.

Peripheral chorioretinal lesions and axial length of the myopic eye.

A study of the retinal periphery of 1,437 predominantly myopic eyes revealed a statistically significant association of four types of peripheral chorioretinal degenerations with increased axial length of the eye. These were white without pressure, pigmentary degeneration, pavingstone degeneration, and lattice degeneration. There was a tendency for both white without pressure and lattice degeneration jointly to affect eyes of individuals 19 years of age and younger. Increasing age was a significant factor in the incidence of pigmentary and pavingstone degenerations, whereas aging significantly reduced the prevalence of white without pressure.

Intravitreal argon and carbon dioxide laser, and xenon arc photocoagulation in vitreoretinal surgery.

Argon laser, carbon dioxide laser, and xenon arc endophotocoagulators have been used intravitreally to produce chorioretinal lesions during the course of the vitrectomy procedure. The advantages and disadvantages of each method of endophotocoagulation are presented. Both the argon laser and the xenon arc have a fiber optic delivery system. The carbon dioxide delivery system has a series of quartz waveguides transmitted through a miniature articulating arm. The advantages of using a carbon dioxide laser are its dual quality to act as both a photocoagulator and phototransector, its lack of pigment dependence, and its ability to deposit its energy in a well-defined area without adverse effects on neighboring ocular tissue.

CO2 laser in vitreoretinal surgery.

Radiation from a CO2 laser has the dual effect of phototransection and photocoagulation. Incisions have been made in scleral-chorioretinal tissue, lens tissue, and the vitreous body (with and without membrane formation). Results indicate that the CO2 laser may be useful in intravitreal surgery. Its simultaneous cutting and coagulating properties may make the experimental transvitreal chorioretinal biopsy reported by Griffin et al [12] and the full-thickness ocular wall resection for small melanosarcomas of the choroid reported by Peyman and Sanders [13] clinical possibilities in the not too distant future. Finally, the effects of CO2 laser radiation on the normal human lens suggests the possibility of the dissolution of cataracts by laser irradiation.

CO2 laser in vitreoretinal surgery: 1. Quantitative investigation of the effects of CO2 laser radiation on ocular tissue.

Scleral, lens, and vitreoretinal tissue was incised using CO2 laser radiation in a controlled and predictable fashion without producing untoward effects on neighboring ocular tissue. The penetration depth of infrared radiation into normal human vitreous was measured and was found to be exceedingly small. A quantitative correlation was observed between the CO2 laser power and the depth of penetration in scleral-chorio-retinal wall incisions and in lens tissue from human eyebank eyes. The results of this investigation suggest that the CO2 laser may be useful in intravitreal surgery, full-thickness scleral-chorio-retinal wall resections, transvitreal chorioretinal biopsy, and even dissolution of cataracts.