Laser photocoagulation of the choroid through experimental subretinal hemorrhage

To study the differential abilities of diode infrared, krypton red, and argon blue-green laser energies to penetrate experimental subretinal hemorrhage and coagulate the underlying choroid.

Autologous, heparinized whole blood was injected beneath the neurosensory retina of pigmented rabbit eyes. After 30 to 60 minutes, confluent patches of moderate or severe diode, krypton, or argon laser burns were applied to adjacent healthy retina and continued into the region of the subretinal hematoma without varying the power setting or focal plane. Histopathologic evaluation of early lesions was performed in a masked fashion, and subretinal hemorrhage thickness was determined with computer-assisted image capture and analysis.

Retina overlying treated subretinal hemorrhage showed no ophthalmoscopically visible signs of photocoagulation with diode energy, a faint gray reaction with krypton energy, and an intense white reaction with argon energy. Histopathologic analysis revealed photocoagulative inner choroidal damage beneath a mean (+/- SD) maximum blood thickness of 0.56 +/- 0.14 mm with severe diode burns, 0.42 +/- 0.09 mm with severe krypton burns, and 0.22 +/- 0.04 mm with severe argon burns.

These data demonstrate that laser penetration of subretinal blood increases with longer wavelengths in vivo. Diode infrared laser energy is capable of penetrating subretinal blood to coagulate the choroid in the absence of ophthalmoscopically visible changes in the overlying retina.