Laser spark for use in ophthalmology

A YAG:Nd³⁺ laser, emitting one of two wavelengths under Q-switching or mode-locking conditions, was investigated from the point of view of its possible use in ophthalmology. A lens with a focal length of 2 cm was used to generate sparks in various media (air, tap and distilled water, physiological solution). A statistical analysis was made of the dependence of the pulse energy in front of the spark on the energy behind the spark and the threshold energies needed for optical breakdown were calculated. A piezoelectric transducer was used in an investigation of shock waves generated by a spark. The peak pressures measured in this way were compared with the results of theoretical calculations carried out using two different approximations; a good agreement was obtained between the experimental and theoretical estimates for distances of the order of 1 cm.