A laser controlled area must be established around a medical laser when there is a risk of maximum permissible exposure (MPE) levels being exceed within the area. This is necessary for compliance with guidelines issued by the DHSS. Before this can be done, the divergence of the laser beam must be determined. Two simple methods for doing this are described in the paper and results are presented for an argon-krypton ophthalmic laser and an Nd-YAG multi-user laser. Depending on the delivery system, beam divergence ranged between 0.86 and 20 degrees at a single installation. MPE levels for the types of laser studied were calculated and the distance within which the MPE might be exceeded was found to range between 1.5 and 33 m. These results were used as a basis for establishing a laser-controlled area.
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