Measurement of the surface temperature of the cornea during ArF excimer laser ablation by thermal radiometry with a 15‐nanosecond time response

Abstract

Background and Objective: The purpose of this work was to develop a temperature measurement system with a nanosecond time response to monitor the transient temperature of the corneal surface during laser refractive surgery. Materials and Methods: Thermal radiation from the surface of the porcine cornea during ArF excimer laser irradiation was measured using a photovoltaic HgCdTe detector with a response bandwidth of 150 MHz. Results: Maximum thermal radiation occurred at 31 AE 4 nanoseconds, which was longer than the time response of the measurement system. The temperature derived from the detected signal reached over 1008C at a¯uence of 80 mJ/cm 2 , which was the ablation threshold, and reached 2408C at a¯uence of 180 mJ/cm 2 . Conclusion: The present system of temperature measurement with a time response of 15.7 nanoseconds revealed that the transient surface temperature of the cornea during ablation is much higher than that previously reported.

Effects of laser repetition rate on corneal tissue ablation for 193‐nm excimer laser light

“…Ishihara et al have studied the surface temperature of cornea during ablation, and found that the peak surface temperature increases with laser fluence [39,40]. At 180 mJ/cm 2 , they reported a value of 2408C surface temperature, and at fluences near 300 mJ/cm 2 , the temperature is as high as approximately 3258C.…”

Evaluation of thermal load during laser corneal refractive surgery using infrared thermography

“…Betney et al, e.g., used a matrix of 10 Â 10 pixels within an area of 1 cm 2 at the centre of the cornea to evaluate the maximum temperature [12], Maldonado-Codina et al evaluated the mean temperature of a matrix of 5 Â 5 pixels within 1.7 mm 2 at the warmest area of the cornea [13]. The spot peak temperature induced by a single laser pulse has been measured by Ishihara et al in order to present a basis for modeling ablation kinetics and transient thermal load [14]. This measurement ideally requires a time constant which is small compared to the rise time of the laser pulse, typically in the range of nanoseconds.…”

Pirenoxine prevents oxidative effects of argon fluoride excimer laser irradiation in rabbit corneas: biochemical, histological and cytofluorimetric evaluations

“…5). Since at the subablative laser fluence and frequency employed (10 mJ/cm 2 , 1 Hz) here, photothermal and photomechanical effects can be considered negligible [38,46]. The detachment of epithelial cells and the destruction of epithelial structure in irradiated and incubated corneas are directly consistent with the considerable lipid peroxidation and increase in necrotic cells.…”

“…The total fluence dose was 200 mJ/cm 2 cornea, achieved by firing 20 pulses of 10 mJ/pulse, at a frequency of 1 Hz. These irradiation conditions, well below the ablation threshold (46 mJ/cm 2 ) [37] and at a low pulse repetition rate, generated a negligible temperature rise [38], hence the only possible direct damage was of a photochemical nature. All corneas were excised at the limbus, washed with PBS and processed for biochemical analysis and histological examination immediately or after incubation.…”