Photocoagulation of the monkey fundus with an
argon-
krypton laser photocoagulator was performed. Lesions produced by
argon and
krypton wavelengths were compared at various power settings, spot sizes, and exposure durations. At low energy levels
argon laser lesions appeared clinically stronger than those produced by the
krypton mode. Lesions in the foveal area produced with the
argon laser demonstrated more extensive microscopic damage to the inner
retinal layers than did those produced with the
krypton laser. Histologically, both modalities affected the outer layers of the retina. However, the
krypton wavelength affected more of the choriocapillaries and the larger choroidal vessels than the
argon wavelengths. Conversely,
argon laser coagulation of the retinal vessels damaged the perivascular tissue in the nerve fiber layer more than the
krypton laser did.
Rupture of Bruch's membrane and
choroidal hemorrhage occurred frequently with the
krypton laser at low energy levels when a small spot size and a short coagulation time were used. Both complications were less likely to occur with
argon burns at similar dosage parameters. By choosing larger spot sizes and longer coagulation times for the
krypton laser, these complications were prevented.