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Steve Gruppetta, Sabah Chetty; Low-cost 3D Retinal Imaging using Structured Illumination. Invest. Ophthalmol. Vis. Sci. 2013;54(15):1465. doi: https://doi.org/.
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The aim of this work is to investigate and develop a first prototype for a low-cost retinal imaging device with axial sectioning capabilities using structured illumination. As structured illumination imaging can provide 3D imaging capabilities without the need for lateral scanning or expensive light sources, it is a viable candidate for an inexpensive diagnostic tool for retinal disease.
The Structured Illumination Ophthalmoscope (SIO) requires the retina to be illuminated using an incoherent sinusoidal pattern and an image that exhibits axial sectioning can be extracted from a series of successive raw images from the device. An illumination modality has been developed based on a Michelson interferometry set-up. Extensive simulations in Matlab have been designed and run to investigate the various key parameters of the SIO, including the spatial frequency of the sinusoidal illuminating pattern, the modulation of the pattern, the number of raw images required to extract an axially-sectioned image and the effect of ocular aberrations on the performance of the SIO. These data were used to build and test a first laboratory-based prototype of the SIO.
The simulation results are presented showing the optimal parameters that yield the best imaging performance (based on axial resolution) and the tolerance in variation of these parameters. We show that the number of images required to yield a single axially-resolved image will vary as it is dependant on the random eye movements but that on average 5-7 consecutive raw frames will be required. The simulation results indicate that the expected axial resolution for the SIO across a population of 100 simulated aberrated eyes ranges from 9.7µm to 25.3µm (5th and 95th centiles) with a median value of 16.1µm. We also present results showing how better control of the modulation of the sinusoidal illuminating pattern can improve the axial resolution further. Images from the first prototype are also presented.
This work demonstrates the imaging capability of a new retinal imaging technology showing the potential of such a device for good axial sectioning, and hence 3D retinal imaging, achieved with an optical system of low complexity (no lateral scanning) and with no expensive components.
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