Visible Light Optical Coherence Tomography of the Retina: From Technical Improvements to Discovering New Bands
- Kho, Aaron M
- Advisor(s): Srinivasan, Vivek J
Optical Coherence Tomography (OCT) has greatly advanced the diagnosis and management of many retinal diseases by enabling in vivo volumetric structural imaging of the retina with high resolution. Usually, retinal OCT is performed at near-infrared (NIR) wavelengths, limiting both axial resolution and contrast for molecules that play a role in vision. Though NIR OCT defines biomarkers that quantify progression of dry age-related macular degeneration (AMD), NIR OCT cannot yet delineate the finest structural and functional changes that define AMD.Visible light OCT has the ability to delineate these changes by providing high resolution and spectroscopic information that can aid in assessing AMD. The higher axial resolution can observe the retinal pigment epithelium (RPE) and Bruch’s membrane (BM) on a sub-micron scale, potentially expanding our knowledge of AMD progression. The molecular contrast can be used for retinal oximetry of blood vessels and potentially photopigment or melanin densitometry which could portend early AMD. Although visible light OCT holds the promise of micron and even unprecedented sub-micron axial resolution and molecular contrast, visible light OCT systems to date have not delivered on this promise. There are many confounding factors that need to be addressed before the full potential of visible light OCT is realized. These include the cost of hardware, size of imaging system, safety considerations limiting light exposure, excess noise in light sources, motion artifacts, chromatic aberrations, and spatially-dependent dispersion. This thesis advances the development of visible light OCT by addressing all of the previously listed issues. With these advances, we can now clearly visualize additional retinal bands in the mouse (and human) retina such as the RPE, BM, inner plexiform layer (IPL) sublaminae, and the dark band inner to the external limiting membrane (ELM).