May 2007
Volume 48, Issue 13
ARVO Annual Meeting Abstract  |   May 2007
Evaluation of Polarization Sensitive Imaging With Adaptive Optics and Optical Coherence Tomography
Author Affiliations & Notes
  • B. Cense
    School of Optometry, Indiana University, Bloomington, Indiana
  • Y. Zhang
    School of Optometry, Indiana University, Bloomington, Indiana
  • R. S. Jonnal
    School of Optometry, Indiana University, Bloomington, Indiana
  • W. Gao
    School of Optometry, Indiana University, Bloomington, Indiana
  • D. T. Miller
    School of Optometry, Indiana University, Bloomington, Indiana
  • Footnotes
    Commercial Relationships B. Cense, patent, P; Y. Zhang, None; R.S. Jonnal, patent, P; W. Gao, None; D.T. Miller, patent, P.
  • Footnotes
    Support Center for Adaptive Optics STC 5–24182 and NEI 5R01 EY014743 HIGHWIRE EXLINK_ID="48:5:1139:1" VALUE="EY014743" TYPEGUESS="GEN" /HIGHWIRE
Investigative Ophthalmology & Visual Science May 2007, Vol.48, 1139. doi:
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      B. Cense, Y. Zhang, R. S. Jonnal, W. Gao, D. T. Miller; Evaluation of Polarization Sensitive Imaging With Adaptive Optics and Optical Coherence Tomography. Invest. Ophthalmol. Vis. Sci. 2007;48(13):1139.

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

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Purpose:: The combination of adaptive optics (AO) and spectral-domain optical coherence tomography (SD-OCT) allows for high-resolution 3D imaging of the microscopic human retina. We have previously demonstrated an AO SD-OCT camera that imaged the 3D morphology of individual cone photoreceptors achieving a voxel resolution of 3x3x6 µm at a high speed acquisition rate of 75,000 A-scans/s. Individuating larger cells, however, such as ganglion and retinal pigmented epithelia (RPE) cells has proven substantially more difficult. The relatively low contrast of these larger cells appears to be a major limitation. As a non-invasive means to enhance contrast, we investigate the benefit of polarization sensitive imaging in AO SD-OCT. This includes determination of phase retardation (birefringence) and fast axis, polarization properties that may help in differentiating neighboring low-contrast cells in various layers.

Methods:: A 2048 pixel linescan detector in a spectral-domain OCT configuration with a Wollaston prism splitting orthogonal polarization states acquired up to 30,000 A-scans/s. The illuminating light was polarization modulated between two states that were orthogonal in a Poincare sphere representation. The relative measurement method that is incorporated this way is not affected by corneal birefringence. AO consisted of a Shack-Hartmann wavefront sensor and a 36 actuator AOptix mirror. Volume scans up to 2° by 2° were acquired through a 6.6 mm pupil and of retinal tissue near the fovea with AO compensation.

Results:: AO-OCT cameras contain a substantial number of optical components, which can potentially induce diattenuation in the instrument and thereby reduce instrument accuracy. Diattenuating (20%) pellicle beam splitters, commonly used in AO cameras, were the only components to limit accuracy of the polarization-sensitive measurements. With the adaptive optics system focusing at the retinal nerve fiber layer to increase the signal to noise of this layer, we measured the phase retardation in a small patch of thin (~25 µm) nerve fiber layer tissue at 7° eccentricity superior to the fovea. The double pass phase retardation per unit depth varied between 0.27°/µm and 0.44°/µm, similar to values found near the optic nerve head of healthy volunteers. A spatial variation in nerve fiber layer birefringence was observed, possibly related to axon density.

Conclusions:: Polarization-sensitive detection permits access to additional information about the retina tissue. Its combination with AO-OCT permits volumetric phase-retardation and optic-axis measurements on a microscopic scale.

Keywords: imaging methods (CT, FA, ICG, MRI, OCT, RTA, SLO, ultrasound) • retina • nerve fiber layer 

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