Purchase this article with an account.
R.S. Jonnal, J. Qu, K. Thorn, D.T. Miller; En-face Coherence Gating of the Retina with Adaptive Optics . Invest. Ophthalmol. Vis. Sci. 2003;44(13):1001.
Download citation file:
© ARVO (1962-2015); The Authors (2016-present)
Purpose: Despite major advances in high-resolution retinal imaging with adaptive optics (AO), less than 0.2% of human retinal cells have been visualized in vivo. The short axial extent and very small index mismatch of retinal cells make detection extremely difficult. We have developed an en-face coherence gated camera equipped with AO that aims to provide improved sensitivity and axial resolution. Methods: Coherence gating in the retina camera was realized with a free-space Michelson interferometer that employed a superluminescent diode for illuminating the retina; voice coil and piezo-electric translators in the reference channel for controlling the gate position; and a CCD array for recording 2-D retinal interferograms. En-face slices of the retina were obtained using a four-step phase shift reconstruction method. The camera was capable of collecting four interferograms in 7 msec. The AO system deployed a 37-actuator Xinetics mirror and a Shack-Hartmann wavefront sensor that provided dynamic correction. The dynamic range and axial point spread width of the system were measured by positioning a planar mirror in the sample channel and sweeping the reference mirror. Through-gating images were collected on a model eye that consisted of a 17 mm achromatic lens, a 7 mm pupil, and an in vitro bovine fundus containing intact retina, choriod and sclera. Preliminary reconstructions were obtained on the in vivo human retina. Results: Axial width of the point spread and dynamic range of the camera were measured near 10 microns and 40 dB, respectively, which is substantially better than current confocal scanning laser ophthalmoscopes (cSLOs) equipped with AO. Reconstructions of the in vitro bovine retina revealed clear layering of the fundus tissue with a measured retinal thickness of 365 microns and well-defined blood vessels of 54 microns diameter. Conclusions: Early results suggest that a coherence gated AO camera should substantially improve our ability to detect single cells in the retina over the current state-of-the-art AO retina cameras, including conventional flood illumination and cSLOs. To our knowledge, this is the first effort to combine coherence gating and AO.
This PDF is available to Subscribers Only