Safety aspects of laser scanning ophthalmoscopes

Safety standards such as American National Standards Institute Z-136.1 do not give clear light-level limitations for laser scanning ophthalmoscopes. To have more than a rough estimation the retinal temperature rise due to intraocular scanning laser illumination was calculated on the basis of a thermal model. The predicted temperature development with time was compared with the calculated effect of other retinal illumination patterns with well-known hazard risks. The similarity of the thermal effect of retinal scanning and extended-source pulsed illumination is discussed and used to give maximum permissible light-level recommendations for the safe use of laser scanning ophthalmoscopes.