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Sung E. Watanabe, Somaia Mitne, Luciana C. Noia, Adriana Berezovsky, Paula Y. Sacai, Solange R. Salomao, Augusto Paranhos, Jr.; Electroretinogram Findings in Patients with Proliferative Diabetic Retinopathy after Argon Laser Photocoagulation. Invest. Ophthalmol. Vis. Sci. 2012;53(14):373.
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The Diabetic Retinopathy Study has shown that panretinal photocoagulation with argon laser reduce the risk of severe visual loss due to proliferative diabetic retinopathy. Consequently some degree of functional retinal impairment should be expected after panretinal laser photocoagulation. The purpose of this study is to evaluate retinal function through full-field electroretinogram (ERG) after panretinal argon photocoagulation in patients with proliferative diabetic retinopathy.
Nine patients (17 eyes, 7 males) aging from 39 to 63 (mean=55±7.6) years with ischaemic diabetic retinopathy had retinal function evaluated by full-field ERG before and after 6 months panretinal laser photocoagulation treatment. ERG was recorded according to the International Society for Clinical Electrophysiology of Vision standard protocol. Wilcoxon test was performed between ERG responses before and after photocoagulation and random effects models were performed to account for the dependence between eyes of the same patient.
Statistically significant reduction in amplitude was found for rod response (p= 0.0000), maximal response (p=0.0000), oscillatory potentials (p= 0.0000), cone response (p=0.0000), and 30-Hz flicker response (p=0.0000) after panretinal photocoagulation when compared to baseline ERG. No statistically significant difference was found for rod latency (p=0.860) and b/a wave ratio (p=0.709), but significantly delayed implicit time for cone response (p=0.0000). Greater amplitude reductions were detected for rod response, maximal response and cone response.
Full-field ERG provided a sensitive measure of retinal function impairment in patients with diabetic retinopathy treated with panretinal argon photocoagulation. Despite the reduction in all ERG responses, the b/a-wave ratio remained unchanged. These findings suggest that, the outer retina seems to be more vulnerable to laser treatment in patients with diabetic retinopathy.
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