High-power lasers in the 1.3- to 1.4-μm wavelength range: ocular effects and safety standard implications

Abstract

This manuscript details recent studies ofocular effects ofpulsed and cw laser radiation at wavelengths of I .3 15 and 1.3 1 8 jsm, and compares comeal, lens and retinal damage thresholds. The results indicate that for the exposure conditions studied, relatively minor changes in pulsewidth and/or wavelength can substantially alter threshold levels and change the tissue site(s) exhibiting the lowest damage threshold. The discussion suggests that these data may be applied to re-assess laser safety standards in the near-a to far-IR transition-region. Also discussed are unique aspects ofthe laser-tissue interaction for these penefrating wavelengths where the incident laser radiation is relatively evenly absorbed throughout the ocular medium and the retina. In such cases of "volurnefric" absorption obsewable manifestations of laser insult may be delayed (hours to days) and may ultimately involve inflammatory responses or other disruption oftissue not directly irradiated by the laser.

Thermal lensing in the ocular media

“…Retinal lesions were not observed for exposures longer than 650 s in the same species. In the rhesus, damage was observed in other portions of the eye for CW cases before any damage was created at the retina (Zuclich, Lund et al 2001). Though retinal damage from a 1300-nm CW exposure with greater than 650 s duration was never achieved in studies using rhesus primates, the same laser conditions caused retinal damage in rabbits.…”

“…1978;Lund, Stuck et al 1981;Birngruber, Gabel et al 1983;Blankenstein, Zuclich et al 1986;Cain, Toth et al 1998;Lund, Edsall et al 1998;Zuclich, Edsall et al 2000;Zuclich, Lund et al 2001;Zuclich, Lund et al 2004;Peri, Turetz et al 2006).…”

“…Experimental safety studies in the 1300 nm regime report retinal damage thresholds for single-pulse exposures of 50 ns -650 s in rhesus subjects, while continuous wave, CW, exposures of 0.1-10 s can produce corneal lesions, but never retinal damage (Stuck, Lund et al 1980;Lund, Stuck et al 1981;Zuclich, Gagliano et al 1995;Lund, Edsall et al 1998;Zuclich, Lund et al 2001;Zuclich, Lund et al 2004;Zuclich, Lund et al 2007). …”

“…Globe geometry details for the rhesus and rabbit eye are discussed in section 2.2.2. (Zuclich, Lund et al 2004) 2 (Zuclich, Lund et al 2007) 3 (Zuclich, Lund et al 2001) 4 (Lund, Stuck et al 1981) (Zuclich, Lund et al 2004) 2 (Zuclich, Lund et al 2007) 3 (Zuclich, Lund et al 2001) 4 (Lund, Stuck et al 1981) 5 (Zuclich, Gagliano et al 1995) 6 (Stuck, Lund et al 1980) …”

“…The deeper cortical cataracts were noted to have an axially tapered lesion diameter. Zuclich et al reported very few instances of cataracts for studies involving 350 s pulses (Zuclich, Lund et al 2001). In these 350 s studies, damage through the anterior tissues of the eye was only observed when the beam was brought to a small spot of 1 mm or less at the surface of the cornea.…”