Temperature Increase in Human Cadaver Retina During Direct Illumination by Femtosecond Laser Pulses

Abstract

The commercial iFS Advanced Femtosecond Laser operating with pulse energies at approximately the lower limit of the range evaluated in this study would be expected to result in a 0.2 degrees C temperature increase and do not therefore present a safety hazard to the retina.

Simulation of the temperature increase in human cadaver retina during direct illumination by 150-kHz femtosecond laser pulses

“…The size of the retina sample was 11 mm × 11 mm. 25 6. We assumed no heat flow due to blood flow in the choroid and sclera.…”

“…Using the model described above, we also calculated the temperature increase in the retina sample using the 60-kHz FS60 46,47 We compared the simulation results for the 150-kHz iFS advanced femtosecond laser to the temperature measured by infrared thermal camera in ex vivo human cadaver retinas previously reported. 25 Based on the thermal sensitivity of the camera (0.08…”

“…In the simulation, the illumination laser beam parameters were assumed to be the same as those applied in the ex vivo experiments previously reported. 25 Some of the thermal properties of the neuro-sensory retina, RPE, and choroid layers were chosen to be identical to those of water. Specifically, the thermal conductivity, density, thickness, and specific heat capacity of such four layers in the model are shown in Table 1.…”

“…Preliminary estimates suggest that 50 to 60% of laser energy passes beyond the cornea with a potential hazard to the retina and iris. [25][26][27] A safety assessment can provide an analysis of exposure relative to established exposure limits. ANSI Z136.1-2007 series provides internationally accepted exposure limits.…”

“…The simulation data were compared with the temperature increase measured by an infrared thermal camera in a human cadaver retina in an ex vivo experiment using a 150-kHz iFS advanced femtosecond laser (AMO Inc., Santa Ana, California) previously reported by our group. 25 In addition, we also simulated the temperature increase using the 60-kHz FS60 laser (AMO Inc., Santa Ana, California), the FEMTEC system (Technolas Perfect Vision Inc., Heidelberg, Germany), and the VisuMax system (Carl Zeiss Inc., Jena, Germany).…”