Choroidal vascular repair following orange dye laser photocoagulation

In order to evaluate the effect of laser photocoagulation on choroidal vessels, moderate laser burns were performed on monkey fundi with a dye orange beam (595 nm) at various intervals for a period of 60 days. After photocoagulation, choroidal vascular casts were prepared by injection of Mercox resin into the carotid arteries, and then observed by scanning electron microscopy. Immediately after photocoagulation, filling defects of the choriocapillaris and medium-sized choroidal vessels were seen in all lesions. By three to five days, restoration of the choroidal microcirculation in the laser lesions had begun. At seven to ten days, filling defects of the choriocapillaris had gradually become undemarcated. By 2 weeks, the sites of the former filling defects were occupied by a loose network of capillaries. At 60 days, the laser lesions had been entirely replaced by newly formed choriocapillaris, composed of narrower lumina and showing a more irregular lobular pattern than normal choriocapillaris.