Far‐ultraviolet laser ablation of the cornea: Photoacoustic studies

Wide bandwidth piezoelectric transducers made of thin (9 m̈m) polyvinylidene fluoride film have been used to make time‐resolved measurements of the stress‐wave generated by far‐ultraviolet (193 nm) laser ablation in corneal tissue in vitro. At high fluence (∼ 250 mJ/cm2), ablation commences within 10 ns (± 5 ns) of the laser pulse and generates short acoustic impulses (∼ 30 ns). The time profile of the ablation, when coupled to the energy requirements for ablation from earlier work, allows the estimation of a temperature and a half‐life for the thermal decomposition of the collagen in cornea. These values do not support a photo‐thermal mechanism for the ablation under the experimental conditions.

[1]  C. Fotakis,et al.  Spectroscopic studies of ArF laser photoablation of PMMA , 1985 .

[2]  J. Krautkrämer,et al.  Ultrasonic Testing of Materials , 1969 .

[3]  V. S. Letokhov,et al.  Laser biology and medicine , 1985, Nature.

[4]  P. H. Key,et al.  Direct etching of polymeric materials using a XeCl laser , 1983 .

[5]  R. Srinivasan,et al.  Laser ablation of organic polymers: Microscopic models for photochemical and thermal processes , 1985 .

[6]  R. Srinivasan,et al.  Ablative photodecomposition: action of far-ultraviolet (193 nm) laser radiation on poly(ethylene terephthalate) films , 1982 .

[7]  Walter T. Smith,et al.  Pyrolysis of soybean protein and an amino acid mixture having the same amino acid composition , 1974 .

[8]  R. Srinivasan,et al.  Kinetics of the ablative photodecomposition of organic polymers in the far ultraviolet (193 nm) , 1983 .

[9]  D. Maurice,et al.  The Cornea and Sclera , 1962 .

[10]  R R Krueger,et al.  Quantitation of corneal ablation by ultraviolet laser light. , 1985, Archives of ophthalmology.

[11]  R. Srinivasan,et al.  Theory of etching of polymers by far-ultraviolet high-intensity pulsed laser- and long-term irradiation , 1984 .

[12]  S. Trokel,et al.  Excimer laser surgery of the cornea. , 1983, American journal of ophthalmology.

[13]  J. Marshall,et al.  An ultrastructural study of corneal incisions induced by an excimer laser at 193 nm. , 1985, Ophthalmology.

[14]  E. B. Higman,et al.  Products from the thermal degradation of some naturally occurring materials. , 1970 .

[15]  F Hillenkamp,et al.  Excimer laser ablation of the cornea and lens. Experimental studies. , 1985, Ophthalmology.

[16]  M. Geis,et al.  Self‐developing UV photoresist using excimer laser exposure , 1983 .

[17]  R. Srinivasan,et al.  Self-developing photoetching of poly(ethylene terephthalate) films by far-ultraviolet excimer laser radiation , 1982 .

[18]  Rangaswamy Srinivasan,et al.  Nanosecond photoacoustic studies on ultraviolet laser ablation of organic polymers , 1986 .