Photocoagulation originally was designed by Meyer-Schwickerath1 for the treatment of retinal lesions in the posterior fundus, especially macular holes. The original equipment soon was replaced by a controlled light source delivered from a xenon tube and accurately applied through an ophthalmoscopic device. This development led to the treatment of more peripheral fundus lesions.
Photocoagulation is based on the following principles: If a high intensity light source is focused onto the retina, the pigment epithelium and the choroid absorb the radiant energy, transforming it into heat. This heat is discharged into the surrounding structures. In order to produce a burn the local production of heat must exceed the dispersal. If the temperature needed to cause this coagulation is attained quickly, little heat can diffuse, and a small dense focus of coagulation occurs. In order to obtain a circumscribed coagulation of 0.5 to 6.0 degrees the necessary heat must
EISSLER R. PhotocoagulationTheoretical Considerations on Its Use in the Peripheral Retina. AMA Arch Ophthalmol. 1960;63(6):993-996. doi:10.1001/archopht.1960.00950020995014