Variability of RPE reaction in two cases after selective RPE laser effects in prophylactic treatment of drusen

Background: The value of prophylactic photocoagulation of soft drusen is unclear. Photocoagulation is usually performed by a continuous wave laser. Methods: We report the cases of two patients with age-related macular degeneration with soft drusen who were treated by selective retinal pigment epithelium (RPE) photocoagulation of a pulsed Nd:YLF (527 nm) laser. Laser parameters were: wavelength 527 nm, number of pulses in a train 500, pulse duration 1.7 μs, energy per pulse 70 μJ, spot size 160 μm, repetition rate 500 Hz. Results: Dosimetry performed individually showed that in both patients laser photocoagulation was performed at the threshold of RPE disruption. None of the laser effects was visible during photocoagulation. They were detectable only by fluorescein angiography. Despite identical photocoagulation parameters the RPE reaction was completely different. In the first patient RPE hyperpigmentation was notable at most photocoagulation sites and the drusen had disappeared after 6 months. In the second patient the laser effects were not visible after 6 months by biomicroscopy and the drusen stayed unchanged. Conclusion: These findings could reflect different repair mechanisms of the RPE after alteration and could represent a sign of a different viable stage:in the life of RPE cells. Close attention should be paid to this phenomenon in the various drusen studies currently under way.