Blood-retinal barrier breakdown caused by diode vs argon laser endophotocoagulation
Y. Sato, B. A. Berkowitz, C. A. Wilson and E. de Juan Jr
Duke University Eye Center, Durham, NC 27710.
We compared the effects of argon and diode laser endophotocoagulation on
blood-retinal barrier breakdown using real-time magnetic resonance imaging
following intravenous gadolinium-diethylenetriaminepentaacetic acid
(Gd-DTPA) injection. Endophotocoagulation was performed on eyes of
pigmented rabbits with either the argon or the diode laser to produce
ophthalmoscopically similar lesions. Magnetic resonance imaging studies
were performed either 2 or 7 days after laser treatment, and coronal
T1-weighted proton images were obtained in the first 20 minutes following
Gd-DTPA injection. The mean signal intensity over a region of interest in
the vitreous cavity was analyzed, and an initial rate analysis was
performed on each time-course curve. Two days after treatment, argon
laser-treated eyes showed significantly greater leakage of Gd-DTPA than
diode laser-treated eyes. The leakage in both groups was substantially
reduced by posttreatment day 7. Histopathologic examination performed 2
days following photocoagulation showed less damage of the retinal pigment
epithelium and more severe occlusion of the choriocapillaris and deep
choroidal vessels in diode laser-treated eyes. These changes may serve to
explain the observed differences in Gd-DTPA leakage.
