Laser photocoagulation of the choroid through experimental subretinal hemorrhage
M. W. Johnson, T. S. Hassan and V. M. Elner
W. K. Kellogg Eye Center, Department of Ophthalmology, University of Michigan School of Medicine, Ann Arbor.
OBJECTIVE: 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. METHODS:
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. RESULTS: 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.
CONCLUSIONS: 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.
