Pulsed laser damage thresholds and laser treatment energy parameters, in vivo, of human aphakic intraocular membranes.

Energy and power density damage thresholds were determined for the perforation of human aphakic pupillary membranes and intraocular lens implants, in vivo, at the focal point of Neodymium-YAG ophthalmic laser systems, at 1,064 nm, which produced Q-switched nanosecond pulses (TEMoo, pulse duration; 20 ns) and mode-locked pulse trains (TEMoo, 9-11 pulses, pulse duration; 30 ps, entire pulse train delivered in 50-70 ns). Pulse energies bracketing the damage thresholds and focal diameter were tabulated. The energy density and power density thresholds for perforation of the pupillary membranes (hereafter referred to as perforation threshold) were slightly lower and power density damage thresholds higher for shorter duration pulses, eg--66 J/cm2 (2,200 GW/cm2) with the picosecond pulse trains vs 80 J/cm2 (2.7 GW/cm2) with the nanosecond pulses and were similar in pseudophakics and aphakics; 78 J/cm2 for pseudophakics vs 83 J/cm2 aphakics, both treated with single nanosecond Nd-YAG pulses, and 68 J/cm2 for pseudophakic vs 66 J/cm2 for aphakic patients treated with picosecond Nd-YAG laser pulse trains. The number of laser pulses and pulse energies required for successful discussion of the pupillary membranes depended not only on the pulse parameters but also on the characteristics of the membrane, such as thickness, nonuniformity, capsular haze, or capsular haze combined with fibrosis.