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Ársaell Arnarsson, Einar Stefánsson; Laser Treatment and the Mechanism of Edema Reduction in Branch Retinal Vein Occlusion. Invest. Ophthalmol. Vis. Sci. 2000;41(3):877-879.
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purpose. To test a hypothesis on the physiological mechanism of the
disappearance of macular edema after laser treatment. The hypothesis is
based on the effect grid laser treatment has on retinal oxygenation and
hemodynamics. It predicts that laser-induced reduction of macular edema
is associated with shortening and narrowing of retinal vessels in
patients with branch retinal vein occlusion (BRVO).
methods. The study included 12 subjects, treated with argon laser
photocoagulation for BRVO and macular edema. Fundus photographs taken
at the time of diagnosis and again after laser treatment, were
digitized, and diameter and segment length of retinal vessels was
measured using NIH-Image program.
results. Macular edema disappeared or was dramatically reduced in all cases
after laser treatment. The diameter of occluded venules constricted to
0.81 ± 0.02 (mean ± SD, P = 0.019) of
the prelaser diameter and adjacent arterioles constricted to 0.78 ± 0.01 (P = 0.008). The laser treatment also led
to shortening of the affected vessels. The final segment length of the
occluded venules was 0.95 ± 0.17 (P = 0.005)
of the length before treatment. The corresponding value for the
adjacent arterioles is 0.95 ± 0.14 (P =
0.008). Control arterioles and venules in the same fundus did not
change in either length or width.
conclusions. These results do not reject the authors’ hypothesis that the
disappearance of macular edema in BRVO can be explained by the effect
the laser photocoagulation has on retinal oxygenation. Increased
oxygenation causes vessel constriction and shortening and lower
intravascular pressure, which reduces edema formation according to
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