Oxidative effects of laser photocoagulation

Paul E. Jennings, Carrie J. MacEwen, Tim J. Fallon, Norma Scott, William M. Haining, Jill J.F. Belch

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    Abstract

    Diabetic proliferative retinopathy is a common and sight-threatening condition. Oxidative stress is an integral and possibly causative part of the pathogenesis. Although laser photocoagulation is usually a beneficial treatment it remains unclear how it works. The possibility that it induces a sudden, temporary increase in free radical activity either by direct thermal damage or by oxygen reperfusion is explored in this clinical study by measuring the oxidative status in the peripheral blood of 13 patients undergoing panretinal photocoagulation. There were significant increases at one hour in malondialdehyde-like material (MDA-LM), 8.1 (6.9-9.6) nmol/mL, to 9.1 (7.6-9.8) nmol/mL, (<0.005); plasma thiols (PSH), 423 (352-457) µm/L, to 444 (382-478) µm/L, (p <0.005) and red cell reduced glutathione (GSH), 1357 (1295-1655) µm/L, to 1480 (1305-1760) µm/L, (p <0.01). Diene conjugates rose over the first hour 0.55 (0.36-0.79) od/mL, to 0.58 (0.34-0.85) od/mL falling to 0.56 (0.36-0.79) od/mL at 2 h but these changes were not significant. At 2 h, MDA-LM 8.4 (6.7-9.6) nmol/mL and PSH 404 (379-462) µm/L had returned to baseline but GSH remained significantly elevated 1500 (1325-1675) µm/L, (p < 0.005 compared to baseline). This is a new observation and in some circumstances such generation of free radicals could explain the mechanism behind the complications of photocoagulation by direct or indirect damage to vascular endothelium leading to increased vascular permeability manifest as macular oedema or choroidal effusions.
    Original languageEnglish
    Pages (from-to)327-330
    Number of pages4
    JournalFree Radical Biology and Medicine
    Volume11
    Issue number3
    DOIs
    Publication statusPublished - 1991

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    Jennings, P. E., MacEwen, C. J., Fallon, T. J., Scott, N., Haining, W. M., & Belch, J. J. F. (1991). Oxidative effects of laser photocoagulation. Free Radical Biology and Medicine, 11(3), 327-330. https://doi.org/10.1016/0891-5849(91)90130-U