Researchers have successfully adapted optical coherence tomography (OCT), a technology commonly used to visualize eye structures, for imaging the inner ear. This innovative adaptation enables clinicians to measure fluid levels within the inner ear and assess their association with the severity of hearing loss. The findings, published in Science Translational Medicine, represent a major advancement in diagnosing and potentially treating hearing-related conditions.
OCT uses light waves to generate high-resolution 3D images of biological tissues, similar in concept to how ultrasound employs sound waves. Traditionally utilized in ophthalmology, OCT has now been repurposed to examine the cochlea and fluid compartments of the ear, a region that has previously been difficult to image with precision. Magnetic resonance imaging (MRI), the most commonly used tool for inner ear imaging, lacks the resolution necessary to accurately assess fluid imbalance, which plays a key role in conditions such as Ménière’s disease and cochlear hydrops. These disorders are known to cause sudden hearing loss and vertigo due to disrupted fluid balance, particularly involving a fluid called endolymph. Until now, measuring endolymph levels in living patients has been extremely challenging. In this proof-of-concept study, OCT has demonstrated the ability to accurately detect variations in inner ear fluid volumes that correlate with the degree of hearing loss.
The study involved 19 patients undergoing ear surgery for various conditions. Among them, six patients had normal ear function, four were diagnosed with Ménière’s disease, and nine had vestibular schwannoma, a benign tumor affecting the nerve that connects the inner ear to the brain. During surgery, the researchers temporarily removed the mastoid bone, which allowed direct imaging access to the cochlea using OCT.
The OCT images revealed that patients with Ménière’s disease and vestibular schwannoma had increased endolymph levels compared to those with normal inner ears. Furthermore, these elevated fluid levels corresponded with more significant hearing impairment. This suggests that OCT could serve as a valuable diagnostic tool to predict disease severity and monitor progression.
While the current application of OCT is limited to intraoperative use, efforts are underway to refine the technology for use in outpatient settings. Researchers aim to enhance the software and image-processing techniques to capture clear images without the need to expose the inner ear surgically. The ability to perform imaging on awake patients would significantly expand the tool’s utility in clinical practice.
In a previous study, Dong and Meenderink showed that spectral-domain OCT could visualize middle and inner ear structures in high resolution and detect sub-nanometer vibrations caused by sound. This depth-resolved vibrometry approach enabled real-time evaluation of cochlear mechanics, supporting OCT’s broader utility in diagnosing auditory pathologies and understanding sound conduction.
One of the key advantages of OCT over MRI is its potential for real-time, repeated imaging. Clinicians could use it to evaluate the immediate impact of treatments such as medications targeting fluid imbalance, by comparing images taken before and after intervention. This approach would dramatically shorten the time needed to assess the effectiveness of different therapies, which often currently involves trial and error over weeks.
Additionally, OCT may prove useful in surgical settings by helping physicians avoid damage to delicate inner ear structures and distinguishing healthy tissue from tumors. A smaller, more cost-effective version of the OCT system is in development, with plans for distribution to surgeons for broader clinical testing.
Beyond diagnostics, OCT may play a transformative role in therapeutic development. Several gene therapies aiming to regenerate damaged hair cells in the inner ear are currently undergoing clinical trials. OCT could enable precise tracking of hair cell regeneration by capturing clear, non-invasive images of these microscopic structures.
This study builds on earlier work by the same team, where OCT was successfully used to image the cochlea in awake animal models. With ongoing advancements, OCT may soon become an essential tool in both diagnosing and treating hearing loss, offering a faster, more reliable, and accessible option compared to current imaging technologies. This new application of OCT could significantly shape the future of inner ear diagnostics and therapy development, just as it revolutionized the management of retinal diseases.
References
- Kim W, Pan DW, Kim BJ, Yang Z, Moran Mojica M, Doherty JK, et al. Human inner ear fluid imbalance detected by optical coherence tomography correlates with hearing loss. Science Translational Medicine. 2025 Jul 23;17(808):eadv3783.
- Dong W, Meenderink SWF. Imaging the Ear Anatomy and Function Using Optical Coherence Tomography Vibrometry. Semin Hear. 2023 Jun 26;45(1):101–9.