1090 nm infrared radiation at close to threshold dose induces cataract with a time delay

Abstract

ABSTRACT.Purpose: To investigate whether infrared radiation (IRR)-induced cataract is instant or is associated with a time delay between the exposure and the onset of lens light scattering after an exposure to just above threshold dose. Methods: Six-weeks-old albino Sprague-Dawley female rats were unilaterally exposed to 197 W/cm 2 IRR at 1090 nm within the dilated pupil. In the first experiment, the animals were exposed with four exposure times of 5, 8, 13 and 20 second, respectively. At 24 hr after exposure, the light scattering in both exposed and contralateral not exposed lenses was measured. Based on the first experiment, four postexposure time groups were exposed unilaterally to 1090 nm IRR of 197 W/cm 2 for 8 second. At 6, 18, 55 and 168 hr after exposure, the light scattering in both lenses was measured. Results: A 197 W/cm 2 IRR-induced light scattering in the lens with exposures of at least 8 second. Further, after exposure to IRR of 197 W/cm 2 for 8 second, the light-scattering increase in the lens was delayed approximately 16 hr after the exposure. Conclusion: There is a time delay between the exposure and the onset of cataract after exposure to close to threshold dose implicating that either near IRR cataract is photochemical or there is a time delay in the biological expression of thermally induced damage.

Temperature-controlledin vivoocular exposure to 1090-nm radiation suggests that near-infrared radiation cataract is thermally induced

“…18,19 The current findings that 96-W∕cm 2 1090-nm IRR with 1-h exposure does not result in direct damage in the lens if the temperature rise is <8°C implicates that IRR-induced cataract is caused by indirect heat absorption in tissues surrounding the lens or, alternatively, possibly by a local inflammatory reaction induced by temperature rise in tissues surrounding the lens, or both.…”

“…Previously, we found that 197 W∕cm 2 1090-nm IRR exposure on the cornea within the dilated pupil for a minimum of 8 s induces cataract with a temperature increase of 10°C in the anterior segment of the eye. 18,19 The purpose of the present study was to investigate if the previously suggested photochemical threshold for near-IRR induced cataract, 1.4 kJ∕cm 2 , 7,14,15 is consistent with irradiance-exposure duration reciprocity, indicating a photochemical nature of cataract formation.…”

Ocular temperature elevation induced by thresholdin vivoexposure to 1090-nm infrared radiation and associated heat diffusion

“…The current experiment was designed to elucidate the temperature increase at 8 s exposure to threshold irradiance of 1090-nm IRR for cataract induction 22 with the long-term intention to investigate irradiance exposure time reciprocity below a threshold temperature for cataract induction.…”

“…22 The presently used optical setup was designed to result in a close to collimated beam through the optics of the eye by focusing the beam in front of the eye (Fig. 1).…”

“…7-10 In a previous study, 22 we found that an in vivo exposure to 197 W∕cm 2 1090-nm IRR on the cornea required a minimum exposure time of 8 s (1.6 kJ∕cm 2 ) to induce light scattering in the lens.…”