Accession Number : ADP020040


Title :   Laser Induced Retinal Damage Thresholds for Annular Retinal Beam Profiles


Descriptive Note : Conference paper


Corporate Author : AIR FORCE RESEARCH LAB BROOKS AFB TX


Personal Author(s) : Kennedy, Paul K ; Zuclich, Joseph Z ; Lund, David J ; Edsall, Peter R ; Till, Stephen ; Stuck, Bruce E ; Hollins, Richard C


Full Text : http://www.dtic.mil/dtic/tr/fulltext/u2/p020040.pdf


Report Date : Jan 2004


Pagination or Media Count : 9


Abstract : The dependence of retinal damage thresholds on laser spot size, for annular retinal beam profiles, was measured in vivo for 3 %, 590 nm pulses from a flashlamp-pumped dye laser. Minimum Visible Lesion (MVL) ED(50) thresholds in rhesus were measured for annular retinal beam profiles covering 5, 10, and 20 mrad of visual field; which correspond to outer beam diameters of roughly 70, 160, and 300 micrometers, respectively, on the primate retina. Annular beam profiles at the retinal plane were achieved using a telescopic imaging system, with the focal properties of the eye represented as an equivalent thin lens, and all annular beam profiles had a 37% central obscuration. As a check on experimental data, theoretical MVL-ED(50) thresholds for annular beam exposures were calculated using the Thompson-Gerstman granular model of laser-induced thermal damage to the retina. Threshold calculations were performed for the three experimental beam diameters and for an intermediate case with an outer beam diameter of 230 micrometers. Results indicate that the threshold vs. spot size trends, for annular beams, are similar to the trends for top hat beams determined in a previous study; i.e., the threshold dose varies with the retinal image area for larger image sizes. The model correctly predicts the threshold vs. spot size trends seen in the biological data, for both annular and top hat retinal beam profiles.


Descriptors :   *THRESHOLD EFFECTS , *LASER BEAMS , *RETINA , *LASER DAMAGE , COMPUTATIONS , RADIATION DOSAGE , LASER SPOTS , LENS(EYE) , RHESUS MONKEYS , SIZES(DIMENSIONS) , VISION , DYE LASERS , IN VIVO ANALYSIS


Subject Categories : Stress Physiology
      Lasers and Masers


Distribution Statement : APPROVED FOR PUBLIC RELEASE