March 2012
Volume 53, Issue 14
Free
ARVO Annual Meeting Abstract  |   March 2012
Spatial Mapping of Retinal Thickness in the Rat using Spectral Domain OCT
Author Affiliations & Notes
  • Diana C. Lozano
    College of Optometry, University of Houston, Houston, Texas
  • Michael D. Twa
    College of Optometry, University of Houston, Houston, Texas
  • Footnotes
    Commercial Relationships  Diana C. Lozano, None; Michael D. Twa, None
  • Footnotes
    Support  NIH/NEI P30 EY 07551
Investigative Ophthalmology & Visual Science March 2012, Vol.53, 5001. doi:
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      Diana C. Lozano, Michael D. Twa; Spatial Mapping of Retinal Thickness in the Rat using Spectral Domain OCT. Invest. Ophthalmol. Vis. Sci. 2012;53(14):5001.

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

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Abstract

Purpose: : Volumetric SD-OCT data is useful for quantifying the spatial thickness distribution of retinal structures. The purpose of this study was to calculate nerve fiber layer/retinal ganglion cell layer (RGCL), nerve fiber layer to inner plexiform layer (RGCL + IPL) and total retinal (TR) thicknesses in the adult brown Norway rat and to generate spatial thickness maps from volumetric SD-OCT data.

Methods: : High-resolution SD-OCT images were captured from 10 adult male Brown Norway rats (average weight = 344 g) using the Spectralis system. Images included 31 individual B-scans separated by 59 µm within a 1.8 x 2.1 x 1.9 mm volume. Images were corrected for lateral magnification using individual axial biometric measurements. Each image volume was cropped and centered on the optic nerve head to define a central 1.3 x 1.3 mm region of interest. A semi-automatic segmentation protocol based on Canny edge detection in combination with other customized segmentation algorithms, was used to delineate the NFL and IPL, while the RPE was manually demarcated. Three-dimensional spatial thickness maps were generated using bilinear interpolation of thickness across individual B-scans. Average thickness of each layer (mean ± SD) was calculated as well as regional thickness by quadrant (superior, inferior, nasal, and temporal). Statistical comparisons between quadrants were assessed using repeated measures ANOVA.

Results: : Average RGCL thickness was 49.3 ± 8.1 µm and this was not quite significantly different by quadrant (P = 0.05). The greatest difference in thickness by quadrant was measured in the temporal (46.1 ± 7.3 µm; 95% CI: 40.9 to 51.3 µm) and nasal quadrants (50.2 ± 5.6 µm; 95% CI: 46.2 to 54.2 µm). Average thickness of the RGC+IPL was 92.6 ± 7.8 µm, which was similar in all quadrants (P = 0.09). Average TR thickness was 204.6 ± 8.8 µm, which also was not significantly different by quadrant (P = 0.18).

Conclusions: : These results suggest that, within a 1.3 x 1.3 mm retinal area, there is a uniform distribution of retinal thickness measurements in the normal rat. These non-invasive in-vivo thickness measurements correlate well with histological studies that show no statistical difference in RGC density by quadrants. The agreement between these studies highlights the usability of in-vivo imaging techniques to quantify local and global structural changes associated with ocular diseases.

Keywords: imaging/image analysis: non-clinical • image processing • imaging methods (CT, FA, ICG, MRI, OCT, RTA, SLO, ultrasound) 
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