Comparative study of ocular damage thresholds from continuous-wave and femtosecond mode-locked lasers

Abstract

In order to provide a direct comparison of the damage thresholds for mode-locked systems to those with continuous-wave (CW) or non-pulsed output, we have performed an experiment with lasers possessing otherwise identical output characteristics. Our work presents an in-vivo minimal visible lesion (MVL) study. Titanium:Sapphire lasers produced 800-nm output for either mode-locked (76 MHz repetition rate, 120 femtosecond) or continuous-wave exposures. Alternating laser exposures were delivered to the paramacular retinal region of rhesus subjects. Laser exposure duration was set to one-quarter second for both types of exposures. Through ophthalmoscopic examination of the fundus, an MVL threshold for damage is established with probit analysis. Approximately 75 data points for each type of exposure were collected. The laser dosage thresholds and confidence intervals for minimal visible damage at twenty-four hours postexposure are reported for mode-locked and CW exposures. Results are compared with published studies conducted at similar pulse duration and similar CW wavelengths.