Laser treatment of retinal diseases by subthreshold laser effects.

The retinal pigment epithelium (RPE) may play an important role in the therapeutic effect of laser photocoagulation. This suggests a benefit from targeting the RPE instead of the sensory retina. Calculating the actual temperature profile after laser photocoagulation, it can be shown that pulse durations have to be in the order of microseconds (micros) to spare the retina from damage. This is consistent with histological findings after laser exposure with repetitive, 5 micros Nd:YLF laser pulses (527 nm). Therapeutic effects have been shown in patients with diabetic macular edema, drusen, and central serous retinopathy.