Search

Laser photocoagulation of the retina using an intraocular probe (endophotocoagulation) has become an important therapeutic tool in vitreoretinal surgery. The Ar-ion laser, the source most frequently used for endophotocoagulation, is an expensive low-efficiency device. Typical powers used in Ar-ion laser photocoagulation are of the order of a few hundred milliwatts in a 100-μm diam spot. Semiconductor diode laser devices producing powers of 200 mW at 780–840 nm have recently become commercially available and offer the potential of replacing expensive water-cooled Ar-ion lasers as sources for retinal photocoagulation. The feasibility of this application of semiconductor diode lasers depends on both the light intensity that can be delivered to the retina and the absorption of the retinal pigment epithelium at the laser wavelength.

One limitation on laser surgery has been excessive damage to normal tissue adjacent to the targeted diseased sites. For example, in laser angioplasty, investigators have caused perforations, aneurysms, spasms, and other forms of inadvertent damage to the arterial wall using cw argon, CO2, and Nd:YAG lasers to ablate obstructions (primarily atherosclerotic plaque). The use of pulsed lasers can reduce thermal diffusion damage; however, they can still cause ablation when accidentally directed at normal tissue. In this study, a selective laser ablative technique is demonstrated by using wavelengths at which there is preferential absorption in the plaque.

The high powered, short pulsed output of the excimer laser has been proposed for use is producing spatially confined tissue, ablation. In vitro studies of ablation of corneal tissue using 193 nm have been previously reported (Trokel, Srinivasan, Braren, 1983). The excimer laser may be useful in producing incisions in the cornea which alter the topography, thereby modifying the optical power of the cornea. The laser may therefore be applied therapeutically to the correction of myopia and astigmatism (that is, in refractive surgery of the eye).