Recent studies of retinal damage due to ultrashort laser pulses have shown that less energy is required for retinal damage for pulses shorter than 1 ns than that for longer pulses. It has also been shown that more energy is required for near-infrared (NIR) wavelengths than in the visible because the light focuses behind the retina, requiring more energy to produce a damaging fluence on the retina. We review the progress made in determining the trends in retinal damage from laser pulses of 1 ns to 100 fs in the visible and NIR wavelength regimes. We have determined the most likely damage mechanism(s) operative in this pulse width regime.

Laser threshold energies for artificial retinal damage from ultrashort (i.e. less than or equal to 1 ns) laser pulses are investigated as a function of both pulse width and spot size. A piece of film acts as the absorbing layer and is positioned at the focus of the Cain artificial eye (17 mm in water). We performed experiments at the focal point, and at two and ten Rayleigh ranges in front of the focus with the damage endpoint being the presence of a bubble coming off the film. Thresholds were determined for wavelengths of 1064 nm, 580 nm, and 532 nm with pulse durations ranging from the nanosecond (ns) to the femtosecond (fs) regimes. For the at-focus data in the visible regime, the threshold dropped from 0.25 (mu) J for a 5 ns pulse at 532 nm to 0.11 (mu) J for a 100 fs, 580 nm pulse. Similarly, for the near infrared (NIR) the threshold changed from 5.5 (mu) J for a 5 ns pulse to 0.9 (mu) J for a 130 fs pulse. These results are discussed in the context of applicable nonlinear optical phenomena.

Extensive research of ultrashort ocular damage mechanisms has shown that less energy is required for retinal damage for pulses shorter than one nanosecond. Laser minimum visible lesion (MVL) thresholds for retinal damage from ultrashort (i.e. < 1 ns) laser pulses occur at lower energies than in the nanosecond (ras) to microsecond (mu s) laser pulse regime. We review the progress made in determining the trends in retinal damage from laser pulses of one nanosecond to one hundred femtoseconds in the visible and near-infrared wavelength regimes. We discuss the most likely damage mechanism(s) operative in this pulse width regime and discuss implications on laser safety standards.

We have made an indirect in-vivo determination of spot size focusing in the rhesus monkey model. Measurement of the laser induced breakdown threshold both in-vitro and in-vivo allow correlation and assignment of a spot size after focusing through the living eye. We discuss and analyze the results and show how trends in minimum visible lesion data should be assessed in light of chromatic aberration. National laser safety standards are based on minimal visual lesion (MVL) threshold studies in different animal models. The energy required for a retinal lesion depends upon may parameters including wavelength and retinal spot size. We attempt to explain trends in reported MVL threshold studies using a model of the eye which allows calculation of changes in retinal spot size due to chromatic aberration.

Recent studies of retinal damage due to ultrashort laser pulses(2,3) have shown that less energy is required for retinal damage for pulses shorter than one nanosecond. Laser minimum visible lesion (MVL) thresholds for retinal damage from ultrashort (i.e. < 1 ns) laser pulses are produced at lower energies than in the nanosecond (ns) to microsecond (mu s) laser pulse regime. We review the progress made in determining the trends in retinal damage from laser pulses of one nanosecond to one hundred femtoseconds in the visible and near-infrared wavelength regimes. We have determined the most likely damage mechanism(s) operative in this pulse width regime and discuss implications on laser safety standards.