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Taeyoon Son, Devrim Toslak, Lei Liu, Xincheng Yao; A holographic waveguide based optometer. Invest. Ophthalmol. Vis. Sci. 2020;61(7):533.
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© ARVO (1962-2015); The Authors (2016-present)
This study is to test if a holographic waveguide (HW) can capture fundus image in front of the eye, and if the image quality is high enough to support wearable see-through quantification of accommodation.
A HW-based benchtop prototype optometer was constructed using an existing green light HW used for display (Fig. a). A collimated LED light and a mask plate were used to project two pinhole images to the retina plane of a model eye. The retinal reflection of the pinhole images was captured by a camera through the HW to compute refractive errors introduced by trial lenses. Squared center of gravity was used to quantify pinhole separation.
The pinhole images were superimposed on each other with no refractive error. Non-zero positive and negative trial lenses converged and diverged the pinhole images, respectively, changing their separation and relative positions, following Scheiner’s principle (Fig. b). Pinhole image separation increased linearly with increasing amount of refractive error until about -16D and +16D. The slope of 10.3 pixels/diopter suggested a 0.1 diopter/pixel resolution. The optometer’s response started to level off at -18D and +18D (Fig. c). The optometer error of measurement within the linear region was 0.054 ± 0.041 (mean ± SD) diopter (Fig. d). High quality refractive error measurement could be achieved with illumination intensities ≥22µW, which was more than one order lower than the permissible light exposure limit (Fig. e).
A holographic waveguide can deliver high quality images at a very safe light intensity to support highly accuracy measurement of ocular refractive error over a wide range. This, and our previous research lay the foundation for future development of HW-based, wearable see-through devices for simultaneous monitoring of eye movement, accommodation and pupil size while patients are engaged in daily activities in their natural environment.
This is a 2020 ARVO Annual Meeting abstract.
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