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US: Researchers illuminate retinas to help stop laser damage

Laser eye safety researchers have demonstrated that retinal cells illuminated with low levels of red light are up to 40% more resistant to damaging laser pulses.

Because the laser pulse wavelength used was in the infrared, and the cells were cultured (not live retinas) there is no current practical use for pilots and others looking for glasses-free resistance to visible laser light. However, this research may open up other avenues as it does indicate that perhaps the retina can be “hardened.”
The researchers studied cultures of human retinal pigmented epithelium (RPE) cells. The cells were exposed to 671 nanometer red light from an array of LEDs. Varying amounts of the red light were used. Then, 24 hours later, the cells were exposed to various powers of a 1 second pulse from a 2000 nanometer short-wavelength infrared laser. The researchers examined the cell cultures, looking for the power level at which lesions occurred 50% of the time (the probit ED50 level).

They found that in control cells (no red LED light exposure), damage occurred around 25 joules per sq. cm, while in cells exposed to red LED lights 24 hours earlier, damage occurred around 35 joules per sq. cm. This is a 40% improvement. Curiously, the maximum protection occurred with red LED illumination levels of 0.40 and 1.60 milliwatts per sq. cm., while an intermediate value of 0.80 mW/cm² was less effective.

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The study was funded by the U.S. Air Force Office of Scientific Research, and was conducted at the Air Force Research Laboratory in San Antonio, Texas. The researchers were Jeffrey C. Wigle, Larry E. Estlack and Kurt J. Schuster.

From SPIE Newsroom/Biomedical Optics and Medical Imaging