Plasma‐mediated ablation of corneal tissue at 1053 nm using a Nd:YLF oscillator/regenerative amplifier laser

Abstract

Plasma-mediated ablations were performed on human donor corneas with a short pulsed Nd:YLF laser system at 1053 nm. The pulses were 60 psec in duration at a repetition rate of 1.0 kHz. The laser beam was oriented perpendicular to the cornea surface. The threshold energy densities for ablation of epithelium, Bowman's membrane and stroma were measured. They were 6.1 +/- 1.8 J/cm2, 21.0 +/- 5.1 J/cm2 and 10.4 +/- 1.8 J/cm2, respectively. The mean rate of tissue removal at the stromal energy density threshold was about 1 micron per pulse. The walls of the laser excisions were smooth with distortions of less than 1 micron. A new quantitative model of plasma-mediated ablation is introduced and found to closely predict the observed results. Based on the promising nature of the experimental data further investigations are planned in the use of a mode locked Nd:YLF laser as an alternative to excimer lasers for refractive corneal surgery.

Study of corneal ablation with picosecond laser pulses at 211 nm and 263 nm

“…A similar value of slope near the threshold can be found from Figure 6 for the ablation of rabbit cornea at 211 nm as n = 1.38, while fi = 2.36 at 263 nm. We would like to point out that in the range near the threshold, our results are in reasonable agreement with previous results of plasma-mediated ablation on the corneal surface by the visible and near-infrared laser pulses, which ranges from ii = 1.4 to fi = 2 [20,21].…”

“…This is due to the fact that n is related to the power with which the plasma absorption depends on the pulse energy, which has been shown to be independent of wavelength [21]. It is not clear, though, why a small value of the facter n (about 0.7) has been measured when the fluence approaches its high end.…”

First safety study of femtosecond laser photodisruption in animal lenses: Tissue morphology and cataractogenesis

“…23,[25][26][27][33][34][35][36][37][38][39][40][41][42][43][44][45][46][47][48] The technology surrounding plasma-mediated ablation (photodisruption) has been refined in its application to the cornea, making it more easily understood and available for its application in the lens. The short pulse duration, low pulse energy, and high peak powers of femtosecond laser photodisruption make it a preferable energy source to picosecond and nanosecond lasers ( Table 2).…”

Intrastromal refractive surgery with ultrashort laser pulses: in vivo study on the rabbit eye

“…Due to the very high intensity of these pulses, it is possible to achieve a cutting effect underneath the surface and inside the bulk of transparent materials by focusing the radiation into the sample [12,14]. The high field intensities at the focus lead to generation and acceleration of free electrons and, thus, to an optical breakdown [13].…”