Cochlea Hair Cell Rescue after a Noise-Induced Hearing Loss using a Low Level Laser Therapy (LLLT)

Aim: To see the effect of LLLT on noise-induced hearing loss. Methods: Eleven rats were exposed to noise (120 dB, 16 kHz, 6 h) and left ears were irradiated at 60J/cm2, 830 nm laser for 12 days. Right ears were control. Hearing levels were measured at frequencies of 4, 8, 12, 16, 32 kHz before noise exposure and after 12th irradiations. Results: The initial hearing levels were 26.5±4.7, 24.5±5.0, 24.0±5.2, 24.0±3.2, 24.5±5.5 dB SPL. After noise exposure, thresholds were 63.5±15.1, 64±16.8, 71.5±11.3, 73.5±15.6, 67.5±14.4 dB SPL in 4, 8, 12, 16, 32 kHz. After 12th irradiation, thresholds of treated ears recovered significantly 21±4.2, 20±3.5, 24±11.9, 24±12.9, 21±2.2 dB SPL and that of the untreated right ears measured 36.3±22.9, 45±15.8, 66.3±22.9, 50±16.8, 43.8±21.4 dB SPL. Conclusion: LLLT may promote recovery of hearing after noiseinduced hearing loss.