Overview of the range of mechanisms

For more than 35 years, a wide range of biomedical research has been conducted in order to understand the biophysical factors which influence laser induced retinal injury. Although the optical effects which influence retinal imaging and the initial physical events which lead to the absorption and dissipation of the laser energy are well understood, the stages of biological damage which take place after the deposition of energy are not so well understood. The greatest body of research was initially centered on the interaction of laser energy with ocular tissues. Much of the research was to derive occupational health and safety standards that provide maximum permissible exposure (MPE) limits. These limits are based both upon the theoretical understanding and the large body of experimental data (including human accident experience). Current laser safety research has recently focused almost exclusively on deriving retinal injury thresholds for sub-nanosecond exposures. Setting limits in this temporal region has been difficult, since there have been conflicting data sets and there are limited data to extrapolate to other spectral regions. Because of the transparency of some ocular tissues, the ocular injury studies offer an opportunity to study all interaction mechanisms with greater ease of viewing the effects directly with greater clarity than working with other biologic tissues.