Wavelength Dependence of Ocular Damage Thresholds in the Near-Ir to Far-Ir Transition Region: Proposed Revisions to Mpes

Abstract

Public reporting burden for this collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources, gathering and maintaining the data needed, and completing and reviewing this collection of information. Send comments regarding this burden estimate or any other aspect of this collection of information, including suggestions for reducing this burden to Department of Defense, Washington Headquarters Services, Directorate for Information SPONSORING / MONITORING AGENCY NAME(S) AND ADDRESS(ES) 10. SPONSOR/MONITOR'S ACRONYM(S)AFRL/HEDO ABSTRACTThis report summarizes the results of a series of IR laser-induced ocular damage studies conducted over the past decade. The studies examined retinal, lens, and corneal effects of laser exposures in the near-IR to far-IR transition region (wavelengths from 1.3-1.4 m with exposure durations ranging from Q-switched to cw). The corneal and retinal damage thresholds are tabulated for all pulsewidth regimes and the wavelength dependence of the IR thresholds is discussed and contrasted to laser safety standard maximum permissible exposure (MPE) limits. The analysis suggests that the current laser standard MPEs could be beneficially revised to: (1) relax the IR MPEs over wavelength ranges where unusually high safety margins may unintentionally hinder applications of recently developed military and telecommunications laser systems; (2) replace step-function discontinuities in the IR MPEs by continuously varying analytical functions of wavelength and pulsewidth which more closely follow the trends of the experimental retinal and corneal ED 50 threshold data; and (3) result in an overall simplification of the safety standard MPEs over the wavelength range from 1.2 m to 2.6 m. A specific proposal for amending the IR MPEs over this wavelength range is presented. SUBJECT TERMS AbstractThis report summarizes the results of a series of IR laser-induced ocular damage studies conducted over the past decade. The studies examined retinal, lens, and corneal effects of laser exposures in the near-IR to far-IR transition region (wavelengths from 1.3-1.4 μm with exposure durations ranging from Q-switched to cw). The corneal and retinal damage thresholds are tabulated for all pulsewidth regimes and the wavelength dependence of the IR thresholds is discussed and contrasted to laser safety standard maximum permissible exposure (MPE) limits. The analysis suggests that the current laser standard MPEs could be beneficially revised to: (1) relax the IR MPEs over wavelength ranges where unusually high safety margins may unintentionally hinder applications of recently developed military and telecommunications laser systems; (2) replace step-function discontinuities in the IR MPEs by continuously varying analytical functions of wavelength and pulsewidth which more closely follow the trends of the experimental retinal and corneal ED 50 threshold data; and (3) result in an overall simplification of the safety standard MPEs ove...

Thermal lensing in the ocular media

“…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). …”

“…Retinal damage threshold studies have been conducted for wavelengths ranging from the ultraviolet (UV) to the infrared (IR) for continuous wave (CW) down to the ultra-short femtosecond pulses (Lund, Stuck et al 1981;Yumita, Shirato et al 1986;Brancato, Praresi et al 1989;Cain, Toth et al 1998;Lund, Edsall et al 1998;ICNIRP 2000;Zuclich, Lund et al 2004;Zuclich, Lund et al 2007). Numerous studies have augmented retinal damage to observe discrete mechanisms contributing to the damage process, such as beam shape, retinal spot size and exposure duration (Zuclich, Lund et al 1999;Cain, Noojin et al 2003).…”

“…Damage threshold studies for the retina at wavelengths between 1300 and 1356 nm, conducted by researchers at Brooks Air Force Base, Texas determined the ED 50 of the retina for pulse durations of 650 s or less in rhesus studies (Lund, Stuck et al 1981;Zuclich, Lund et al 2004;Zuclich, Lund et al 2007). Retinal lesions were not observed for exposures longer than 650 s in the same species.…”

“…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) …”

“…Zuclich, Lund et al 2007, Lund, Edsall et al 2000, and Lund and Edsall 1999 have developed a process for expressing a theoretical fit to the TIE ED 50 data as a function of wavelength based upon thermal and thermochemical ocular-tissue properties (Lund and Edsall 1999;Lund, Edsall et al 2000;Zuclich, Lund et al 2007). Though not by conventional definition, they refer to this theoretical fit as an action spectra.…”