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M. Rehak, M. Hollborn, S. Uhlmann, P. Köferl, P. Wiedemann, A. Bringmann; Treatment of Branch Retinal Vein Occlusion by Arteriolar Constriction (Crimping Technique) Does Not Increase Retinal Ischemia. Invest. Ophthalmol. Vis. Sci. 2009;50(13):498.
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Arterial crimping is a laser technique reported by some authors as effective method for the treatment of macular edema (ME) in patients with branch retinal vein occlusion (BRVO). While this procedure may decrease the arterial pressure and facilitate the draining of ME, some authors assumed that this technique increases the severity of retinal ischemia. We determined in a rat model of BRVO, followed by arterial crimping, the changes in the expression of factors implicated in the development/resolution of ME and the retinal oxygen concentration pO2.
In one eye of adult Brown Norway rats (n=12), retinal veins were photocoagulated using a blue-green argon laser. In the "crimping group" (n=12), laser induced constriction of the afferent arteriole was performed 30 minutes after BRVO. Untreated eyes served as controls. One and 3 days after BRVO the retinal pO2 was measured, the eyes were enucleated, and the retinal mRNA levels of following factors were determined with real-time RT-PCR: VEGF-A (Vegfa), PEDF (Pedf), interleukin-6 and -1β (Il6, Il1β), the potassium channel Kir4.1, and aquaporins 1 and 4.
Retinal pO2 was decreased in the eyes with BRVO compared to controls. No difference in pO2 was observed between the groups with and without arteriolar crimping. The expression of Vegf was upregulated 1 day after BRVO and returned to the control level after 3 days. Il6 and Il1ß were upregulated in both animal groups after 1 day. After 3 days, Il1ß remained upregulated whereas Il6 was decreased in the "crimping group". Kir4.1 and aquaporins were downregulated after BRVO in both groups and time intervals.
Arteriolar crimping does not increase retinal ischemia due to BRVO. The upregulation of the expresion of VEGF was slightly reduced in animals treated by crimping technique, but the difference to the untreated animals was not significant. No significant differences between animals with and without arterial crimping were observed for all investigated factors with the exception of IL-6.
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