Abstract: Laser energy absorbed in cells can affect the cellular materials through a variety of physical mechanisms. For pulses longer than a microsecond in duration, damage at threshold levels is due to thermal effects. However, for supra-threshold pulses, or for threshold levels at shorter pulse durations, other physical mechanisms may be the source of damage. The most likely mechanisms are the generation of large pressures, and the creation of bubbles. This is especially true for heavily pigmented cells, such as the retinal pigment epithelium, where large energy densities can be attained in the strongly absorbing pigments. We describe how the generation of large pressures depends on laser pulse duration and energy, as well as the properties of the absorbing pigment. Extremely large negative pressures can be generated in the core or the absorber, possibly resulting in the explosion of the absorbing pigment within the cell. We also discuss the conditions for which damaging bubbles are likely to be formed. !16
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