Based on their own investigation on the influence of aberrations on LIOB Vogel et al. concluded that minimizing aberrations is essential for clinical laser applications [ 4].
To investigate the influence of aberrations on optical breakdown threshold pulse energy we developed an adaptive optics femtosecond laser instrument which enables both the correction of aberrations and the detection of optical breakdown in a water based eye model.
A previous report by Vogel et al. [ 4] investigated the influence of aberrations on nanosecond LIOB by introducing additional wave front distortions of up to 18.5 λ with a resulting increase in breakdown threshold and plasma transmission.
Visualization in this study is therefore focused on video imaging of long-lasting gas bubbles, specifically the influence of aberrations on the threshold for gas bubble generation and on the dynamics of gas bubble motion.
We investigated the influence of aberrations from the laser system, the optical pulse delivery system, and a model eye on the optical breakdown in comparison to the diffraction limited beam.
Our approach differs from that described in [ 4] in that we investigate the influence of aberrations on femtosecond LIOB not by introducing additional aberrations but by correcting any present aberrations including these which conventionally cannot be influenced, e.g. in the subject eye.
Future studies using time-resolved photography to determine optical breakdown with the creation of a cavitation bubble as criterion for threshold or using pump-probe experiments to investigate the plasma generation and consecutive effects could clarify the influence of aberrations on train pulses and determine a more reliable threshold value.
The iris behaves as a diaphragm, modifying the amount of light entering the eye; probably of greater significance than control of the light entering the eye is the influence on aberrations of the optical system; the smaller the pupil the less serious, in general, are the aberrations.
The considered influences of aberrations on LIOB and their consequences for retinal safety during ophthalmic surgery show the requirement for aberration correction.
In general, the focal spot cannot be transformed to an irregular shape under the influence of spherical aberration.
