Laser Speckle Flowgraphy Examination of Choroidal Microcirculation After Scattered Fundus Photocoagulation

Abstract

Abstract: : Purpose: To study alterations of choroidal microcirculation after scattered photocoagulation, using a laser speckle flowgraphy (LSFG) system. Methods: Forty–nine pigmented rabbits were studied. Diode laser (810nm) photocoagulation was performed in thirty–nine eyes. Thirty five to forty scattered burns were placed at the inferior part of each fundus, one disc diameter away from the optic nerve head. Choroidal microcirculation was examined one week, two weeks, four weeks, 12 weeks, and 24 weeks after photocoagulation using an LSFG system. Square blur rates (SBR), a quantitative index of relative blood velocity, were calculated at interested lesions with an LSFG analysis system. The interested lesions included the photocoagulated scar sites, those between the scars (inter–coagulated sites), and those away from the scars (non–coagulated sites). In addition, we did a similar experiment in other ten eyes after a red dye laser (630nm) photocoagulation. Results: Throughout the examination periods, the SBR had significantly decreased at the coagulated sites, compared with those at the inter–coagulated sites (p<0.001). The latter SBR had significantly decreased in comparison to those at the non–coagulated sites (p<0.001). Similar results were obtained in the experiments using the red dye laser. Ratios of the SBR at the inter–coagulated sites versus those at the coagulated sites significantly decreased at two weeks (p<0.05), four weeks (p<0.05), 12 weeks (p<0.001) and 24 weeks (p<0.001), compared with those at one week. Similarly, ratios of the SBR at the non–coagulated sites versus those at the coagulated sites significantly decreased at 12 weeks and 24 weeks. In the red dye laser experiments, although the SBR ratios of the inter–coagulated sites versus the coagulated sites showed no significant changes throughout the experiment preiods, the SBR ratios of the non–coagulated sites versus the coagulated sites,significantly decreased at 12weeks (p<0.05). Conclusions: It was suggested that laser photocoagulation not only reduced the anatomical structure of the choroidal vasculature but reduced the blood flow of the residual vasculature at the inter–coagulated sites and the surrounding non–coagulated sites.

Keywords: imaging/image analysis: non-clinical • choroid • laser