Abstract
Purpose :
Visible light Optical Coherence Tomography (OCT) has recently emerged for ultrahigh resolution and functional imaging in biological tissues. It is particularly promising for retinal imaging, where layers are thin, and important chromophores have distinct extinction spectra in the visible light range. Here, we investigate whether spatially-dependent dispersion (SDD) compensation can improve the quality of visible light OCT images and allow us to visualize more layers in the rodent eye.
Methods :
A spectral domain visible light OCT ophthalmoscope was built for in vivo mouse retinal imaging with a center wavelength of 587 nm. The system had an axial and transverse resolution of 1.4 μm and 7.6 μm in air, respectively. To compensate chromatic dispersion, which may vary with axial and transverse position, we also introduce SDD correction. This is especially important in visible light OCT systems due to broad bandwidths and large dispersion of optical glass and aqueous media. Four to six weeks old BALB/c and C57BL/6J mice were imaged. Data sets were acquired with 1.2 mm transverse range with frames having variable offsets (0-5 μm) for speckle reduction.
Results :
Compensation of spatially-dependent dispersion allowed us to achieve high axial resolution at all axial and transverse positions. We were able to visualize Inner Plexiform Layer (IPL) sublaminae and two layers in the Retinal Pigment Epithelium/Bruch’s Membrane (RPE/BM) complex. The proximal thicker RPE/BM layer, possibly RPE, was 3.2±0.6 μm and 4.8±0.6 μm in BALB/c and C57BL/6, respectively. The distal thin RPE/BM layer, possibly BM, was 1.8±0.5 μm and 1.9±0.5 μm in BALB/c and C57BL/6, respectively.
Conclusions :
Dispersion in the visible light regime deteriorates the axial resolution significantly in visible light OCT and SDD must be considered to optimize image quality. By compensating SDD, we resolved both the IPL sublaminae and two layers within the RPE/BM complex in both pigmented and unpigmented mice. Our results can aid in better interpreting these layers.
This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.