Abstract
Purpose :
Here, we use visible light Optical Coherence Tomography (OCT) to investigate the inner segment (IS) myoid (“m”) and ellipsoid (“e”) zones in the C57BL/6J mouse retina.
Methods :
A free-space visible light spectral / Fourier domain OCT system was used for in vivo retinal imaging of C57BL/6J (n=11, 9.87 ± 7.92 months, 9 males, 2 females) mice from The Jackson Laboratory. The full spectral width used for imaging was 259 nm and the axial resolution was 1.0 μm in tissue. Eight repeated volumetric datasets with 512 a-lines and 128 b-scans each were acquired with a 1 mm fast axis range and a 0.12 mm slow axis range, for speckle reduction. Each volumetric dataset was acquired in 17.5 seconds. Raw OCT data were motion-corrected and averaged along the slow axis to yield high-quality cross-sectional images (Figure 1A). The region near the ELM was fitted at each transverse location in 2x upsampled, background-corrected line profiles. A Gaussian plus offset model was employed to represent the ELM and surrounding (outer nuclear layer and IS) reflectivity, respectively (Figure 1B). Line profiles with R-squared > 0.91 and Gaussian (ELM) standard deviation < 4 pixels were retained, normalized to the offset, and displayed as an image (Figure 1C). All retained line profiles for each data set were averaged, yielding relative intensity profiles.
Results :
We observed a subtle reflectivity division in the IS, which was revealed to consist of a more reflective, “m” zone, and a less reflective, “e” zone (Figure 1C). The division was present to some degree in both younger and older mice (Figure 1D).
Conclusions :
Our results show that visible light OCT can distinguish a subtle IS reflectivity division in the mouse. Findings were consistent with prior human OCT study (Srinivasan et al., TVST 2022) which showed the myoid zone to be more reflective than the inner ellipsoid, and cytochrome C immunostaining in the mouse (Cuenca et al., Prog. Retin. Eye Res. 2020) which shows a myoid on the order of 5 microns in length.
This abstract was presented at the 2023 ARVO Annual Meeting, held in New Orleans, LA, April 23-27, 2023.