Abstract. We measured threshold temperatures for cell death resulting from short (0.1-1.0 s) 514-nm laser exposures using an in vitro retinal model. Real-time thermal imaging at sub-cellular resolution provides temperature information that is spatially correlated with cells at the boundary of cell death, as indicate by post-exposure fluorescence images. Our measurements indicate markedly similar temperatures, not only around individual boundaries (single exposure), but among all exposures of the same duration in a laser irradiance-independent fashion. Two different methods yield similar threshold temperatures with low variance. Considering the experimental uncertainties associated with the thermal camera, an average peak temperature of 53 ± 2• C is found for laser exposures of 0.1, 0.25, and 1.0 s. Additionally, we find a linear relationship between laser exposure duration and time-averaged integrated temperature. The mean thermal profiles for cells at the boundary of death were assessed using the Arrhenius rate law using parameter sets (frequency factor and energy of activation) found in three different articles. C 2011 Society of Photo-Optical Instrumentation Engineers (SPIE).
The temporal modulation of light from halophosphate, triphosphor and multiband fluorescent lamps (controlled by a conventional choke circuit) was measured as a function of wavelength. Within each category, all lamps had similar functions for peak-peak modulation. At the short-wavelength end of the visible spectrum all lamps showed a modulation near 100%.Halophosphate and multiband lamps had a low modulation at the long-wavelength end of the spectrum and gave the lowest overall modulation. Certain deluxe lamps had a modulation greater than 80% throughout the spectrum. The modulation of photopic energy, and energy transduced by the photoreceptors was calculated. Triphosphor lamps gave greater modulation than halophosphate, the lowest modulation being from warm-white halophosphate lamps.
Abstract. We propose a rate process model for describing photochemical damage to retinal cells by short wavelength laser exposures. The rate equation for photochemical damage contains a positive rate that is temperature independent, and a negative (quenching) rate that is temperature dependent. Using the traditional Arrhenius integral to describe thermal damage, we derive damage threshold doses for both thermal and photochemical mechanisms, and show that the model accounts for the sharp transition from thermal to photochemical damage thresholds that have recently been observed in an in-vitro retinal model. C 2011 Society of Photo-Optical Instrumentation Engineers (SPIE).
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