Originally Posted by Chesty
The energy density (measure of energy per unit of area) of the l@ser beam increases as the spot size decreases. This means that the energy of a l@ser beam can be intensified up to 100,000 times by the focusing action of the eye for visible and near infrared wavelengths. If the irradiance entering the eye is 1 mW/cm2, the irradiance at the retina will be 100 W/cm2. Even a 4% reflection off an optic can be a serious eye hazard. Remember a low power l@ser in the milliwatt range can cause a burn if focused directly onto the retina.
Which is very interesting, but if you read BS-EN60825 and the definition of MPE you'll find that the numbers on the graph relate to energy levels that can cause damage at the retina (amongst other things) so this is already taken into account, because the people writing these standards aren't
complete idiots*.
PDR
*I gather a few of the parts are still on back-order