Illumimaton intensities of 6 indirect opthalmoscopes and 5 slit lamps were measured and calculated. The results showed the retinal irradiance from these instruments is quite high with dilated pupils ahd clear media. Although such illuminating intensity is a potential risk factor for the human retina, with careful use and reduced intensity, they are relatively safe. We suggest that ophthalmologists try their best to avoid using brighter source beyond useful illumination and unnecessary wide slit. （Chin J Ocul Fundus Dis,1992,8:133-137）