Abstract
Purpose :
Retinal ganglion cell (RGC) loss is a hallmark of glaucoma, and RGC dendrites which stratify in the off sublamina of the inner plexiform layer (IPL) may exhibit early glaucomatous changes. However, the in vivo visualization and quantification of the IPL remains challenging due to insufficient achievable contrast. Here, we used our achromatized visible light OCT, with a hardware spectral shaping method, to reduce sidelobes in the point spread function (PSF). We tested whether this technology can visualize the subtle differences in reflectivity due to IPL lamination.
Methods :
A fiber-based, spectral/Fourier domain visible light OCT system for human retinal imaging was built. To reduce PSF sidelobes, we developed a diffractive optical setup to shape the spectrum (Figure 1A). The broadband light is spatially dispersed and focused on a grating light valve spatial light modulator (GLV-SLM). With appropriate control of the GLV-SLM, the original spectrum can be shaped to a desired spectrum. The GLV-SLM can also reduce the short wavelength light exposure during subject alignment. A scanning protocol with continuous volumes spaced along the final image axis was used. Then, two dimensional motion correction and averaging were applied to generate one cross-sectional image.
Results :
In Figure 1B, the original spectrum was shaped to Hamming window with 565 nm center wavelength for ultrahigh resolution (UHR) imaging, and 625 nm center wavelength for alignment. The sidelobes of the axial PSF are suppressed (Figure 1C). Our preliminary result (Figure 2) indicates that human IPL lamination can be resolved.
Conclusions :
We developed a novel spectral shaping method to further increase the contrast of visible light OCT. IPL lamination was clearly resolved. This method may provide additional morphological information to diagnose and monitor retinal diseases and glaucoma.
This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.