April 2014
Volume 55, Issue 13
Free
ARVO Annual Meeting Abstract  |   April 2014
Retinal Changes Associated with Hibernation Revealed by OCT Imaging
Author Affiliations & Notes
  • Wei Li
    Unit of Retinal Neurophysiol, National Eye Institute, NIH, Bethesda, MD
  • Yichao Li
    Visual Function Core, National Eye Insitutte, Bethesda, MD
  • Fengyu Qiao
    Unit of Retinal Neurophysiol, National Eye Institute, NIH, Bethesda, MD
  • Joe G Hollyfield
    Cole Eye Institute/Ophthalmic Research, Cleveland Clinic, Cleveland, OH
  • Haohua Qian
    Visual Function Core, National Eye Insitutte, Bethesda, MD
  • Brent A Bell
    Cole Eye Institute/Ophthalmic Research, Cleveland Clinic, Cleveland, OH
  • Footnotes
    Commercial Relationships Wei Li, None; Yichao Li, None; Fengyu Qiao, None; Joe Hollyfield, None; Haohua Qian, None; Brent Bell, None
  • Footnotes
    Support None
Investigative Ophthalmology & Visual Science April 2014, Vol.55, 2174. doi:
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    • Get Citation

      Wei Li, Yichao Li, Fengyu Qiao, Joe G Hollyfield, Haohua Qian, Brent A Bell; Retinal Changes Associated with Hibernation Revealed by OCT Imaging. Invest. Ophthalmol. Vis. Sci. 2014;55(13):2174.

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      © ARVO (1962-2015); The Authors (2016-present)

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Abstract
 
Purpose
 

To evaluate in vivo changes in retina and choroid in active and hibernating 13-line ground squirrel using ultra high resolution Spectral Domain Optical Coherence Tomography (OCT).

 
Methods
 

Thirteen-line ground squirrels (n=7, 8-12 months) were imaged by OCT (Envisu R2200 UHR, Bioptigen) before, during, and after hibernation and post-mortem. B-scans (20 frames @ 1000 A-scans/B-scan) were collected ventral to the visual streak at <2µm (axial) & 11µm (lateral) resolution. Image frames were coregistered and averaged. Profiles were corrected for imaging system background and responsivity to yield OCT signal amplitude. OCT signal morphology from retinal lamina were compared to histomorphology results. Quantitative changes to OCT signal amplitude were obtained from different metabolic states.

 
Results
 

Non-hibernating animals showed bright, well-delineated outer retina morphology that correlated to the histology of this animal. Measurements of IS (20.8±1.5µm) and OS (6.5±1.1µm), as well as dimensions from the myoid (~12µm) and ellipsoid (~8µm) regions were similar to that reported previously (Reme & Young, 1977). During hibernation a dramatic reduction in signal amplitude and contrast was observed, which did not result in significant changes to thicknesses of any outer retinal layer relative to non-hibernating conditions. Choroidal thickness was significantly reduced (44%, p=.0008) during torpor, but returned to normal by 1 hr post-hibernation. Bright band signal amplitude decreased significantly in the IS-ellipsoid (p<.0001), OS (p=.001), RPE (p=.004) and Sattler’s layer of the choroid (p=.0007). The bright band that showed the greatest change in signal amplitude (~50%) corresponded to the ellipsoid region where mitochondria reside. Signal amplitude in all lamina was partially and fully restored to pre-hibernation levels after 1-3 & 24 hours of recovery, respectively. Results from post-mortem animals were similar to those observed in animals under deep hibernation.

 
Conclusions
 

OCT retinal signal amplitude and morphology contrast is substantially reduced during hibernation. The most dramatic changes occurred in the ellipsoid region, which suggests that OCT is capable of discerning changes to mitochondrial architecture, number or volume as a result of changing metabolic activity required for animals that undergo circannual hibernation.

     
Keywords: 552 imaging methods (CT, FA, ICG, MRI, OCT, RTA, SLO, ultrasound) • 600 mitochondria • 688 retina  
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