Green Laser Light Activates the Inner Ear - New Research Findings

A new study conducted at Medical University Hannover published in Journal of Biomedical Optics (volume 14, issue 4, page 044007;ISSN 10833668) investigated the use of laser light to provide localized activation of the cochlea, as measured by eliciting optical-induced ABRs. The study's abstract is provided here;for a copy of the complete article or a subscription to the journal, visit spie.org

Title: Green Laser Light Activates the Inner Ear

Authors: Wenzel, G.I.;Balster, S;Zhang, K;Lim, H.H;Reich, U;Massow, O;Lubatschowski, H;Ertmer, W;Lenarz, T;and Reuter, G.

Abstract: The hearing performance with conventional hearing aids and cochlear implants is dramatically reduced in noisy environments and for sounds more complex than speech (e. g. music), partially due to the lack of localized sensorineural activation across different frequency regions with these devices. Laser light can be focused in a controlled manner and may provide more localized activation of the inner ear, the cochlea. We sought to assess whether visible light with parameters that could induce an optoacoustic effect (532 nm, 10-ns pulses) would activate the cochlea. Auditory brainstem responses (ABRs) were recorded preoperatively in anesthetized guinea pigs to confirm normal hearing. After opening the bulla, a 50-mum core-diameter optical fiber was positioned in the round window niche and directed toward the basilar membrane. Optically induced ABRs (OABRs), similar in shape to those of acoustic stimulation, were elicited with single pulses. The OABR peaks increased with energy level (0.6 to 23 muJ/pulse) and remained consistent even after 30 minutes of continuous stimulation at 13 muJ, indicating minimal or no stimulation-induced damage within the cochlea. Our findings demonstrate that visible light can effectively and reliably activate the cochlea without any apparent damage. Further studies are in progress to investigate the frequency-specific nature and mechanism of green light cochlear activation.