Optical Coherence Tomography with Fluorescein Optical Clearing for Transscleral Image Guidance

Optical coherence tomography (OCT) is a non-invasive, three-dimensional imaging modality demonstrated to yield a wealth of high-resolution structural and functional information in a variety of biomedical imaging applications. However, there is a significant limitation on the penetration depth of the modality in most tissues due to their high optical scattering, hindering imaging of more deeply embedded targets. In ophthalmic applications, this makes transscleral imaging of targets such as suprachoroidal injection volumes, lesions, and malignancies challenging. Here, we investigate the novel application of fluorescein, a commonly applied biomedical dye, as an optical clearing agent for increasing the depth of OCT imaging in scleral tissues. The effect is characterized in ex-vivo models including the sclera of porcine and human eyes, examining its time and concentration dependence, reversibility, and potential for application in the enhancement of intrasurgical trabeculectomy image guidance. We demonstrate that fluorescein can serve not only as a biomedical fluorophore, but also as an optical clearing agent capable of significantly increasing OCT imaging depth in tissue. As a common and accessible ophthalmic agent with a long history of clinical application, we believe that this new potential use could have substantial positive impact in the enhancement of biomedical imaging in scattering tissue.