Corneal dose response from exposure to a Q-switched laser at a central wavelength of 1645 nm using a rabbit model.

Abstract

Significance: Laser safety studies of the eye are well documented for visible wavelength and continuous wave lasers. There are fewer experimental results for infrared wavelengths and pulsed lasers.

Aim: We aim to fill the gap at 1645 nm for single nanosecond pulse duration exposures of rabbit cornea and determine the threshold radiant exposure to generate lesions 50% of the time (estimated dose ${\mathrm{ED}}_{50}$ ).

Approach: Images of the cornea during exposures were acquired using slit lamp microscopy and optical coherence tomography. A histological analysis helped provide dosimetry relationships with morphology and mechanisms of the damage.

Results: We measured the energy ${\mathrm{ED}}_{50}$ value at $3.86\pm 0.085\mathrm{mJ}$ utilizing the slit lamp biomicroscopy. Incorporating the experimental spot size diameter, this corresponds to a peak radiant exposure of $102J/{\mathrm{cm}}^2$ . By contrast, the average radiant exposure ${\mathrm{ED}}_{50}$ over a 1-mm diameter limiting aperture as per the ANSI Z.136 convention was $0.49J/{\mathrm{cm}}^2$ . Additional analysis via optical coherence tomography (OCT) and histology examined the severity and degree of damage.

Conclusion: This experimental approach performed well to characterize damage and identify damage thresholds to inform the laser safety standard community of the accuracy of current exposure limits.