  Laser systems emitting radiation in the visible and near infrared region are
potentially hazardous for the retina of the human eye. This can result in
irreparable injuries due to photomechanical, photothermal or photochemical
light-tissue interactions. This investigation focuses on the photothermal
interaction for which a computer model is used to simulate the thermal behavior
of the retina and to predict the injury threshold values. The most important
factors are the wavelength of the radiation, the exposure time and the
irradiance profile on the retina. For performing safety evaluations and
classifications the laser safety standard IEC 60825-1:2014 has to be
considered. These evaluations are based on emission limits which depend on the
same above mentioned factors. According to the IEC 60825-1:2014, non-uniform
retinal images are treated by an image analysis where an averaged spot size is
used. This averaged size is calculated by the extent of the irradiance profile
along two orthogonal directions. Unlike the laser safety standard, the computer
model predicts the injury thresholds for an irradiance profile on the retina
without averaging the spot size. In this investigation, a broad variety of
non-uniform retinal images is investigated with regard to the injury thresholds
predicted by the computer model and to the classifications according to the
laser safety standard.
