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

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.

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 ${\mathrm{ED}}_{50}$ ).

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.

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.

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.