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- Ingling, Allen W, et al.
(författare)
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Fixation stability readily obtained from confocal color fundus imaging
- 2015
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Ingår i: Investigative Ophthalmology and Visual Science. - 0146-0404 .- 1552-5783. ; 56:7, s. 515-515
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Tidskriftsartikel (refereegranskat)abstract
- PurposeStabile fixation underpins most visual tasks such as reading, and is important for accurate assessment of visual function and treatment. Retinal imaging instruments average images over time to improve the signal to noise ratio, discarding useful eye movement data. We determined whether the frame-to-frame motion of the retina during non-mydriatic color fundus imaging could provide fixation stability measures, e.g. Bivariate Contour Ellipse Area (BCEA). MethodsNon-mydriatic color fundus images were acquired using the Digital Light Ophthalmoscope (DLO). Twenty subjects with varied fundus pigmentation were tested without mydriasis. The DLO uses a digital light projector with LED light sources to provide the illumination for both confocal imaging and fixation stimuli. The DLO projects a series of lines across the fundus that is synchronized to the 2D CMOS sensor, providing high contrast confocal imaging. Monochromatic 40 deg images were acquired with alternating red and green LED illumination at 14.3 Hz and overlayed to present a pseudo-color image to the operator in real time. To reduce pupil constriction and patient discomfort, the green LED was long-pass filtered with a 570 nm filter. A 1.5mm entrance pupil and time-averaged power of <30 uW were used. Images were aligned automatically with custom software (MATLAB) using cross-correlation and 2D translation. A canvas of twice the image size was used to allow image alignment despite moderate eye movements. Blinks and large saccades were discarded and BCEA was computed. ResultsThe image alignment algorithm successfully aligned nearly all the frames, rejecting 3.7%, and allowing fixation stability to be computed from color fundus image data. The BCEA for 1 standard deviation was 2.97 log minarc2 for all subjects and both the red and yellow-orange illumination. There was no difference between the BCEA for red or yellow-orange illumination (t = .86). ConclusionsThe color DLO records sufficiently high quality images to reliably calculate measures of fixation stability. Despite recruiting an especially challenging population that included dark fundi, small pupils, high refractive errors, and media issues, we achieved success in all subjects tested to date.
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| 2. |
- Muller, Matthew S, et al.
(författare)
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Non-mydriatic color fundus imaging with the Digital Light Ophthalmoscope
- 2015
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Konferensbidrag (refereegranskat)abstract
- Purpose To provide non-mydriatic confocal color fundus imaging of sufficient quality for screening for diabetic retinopathy despite dark fundus pigmentation, small pupil, high refractive error, or other anterior segment issues. MethodsNon-mydriatic color fundus images of 34 volunteers (aged 39.2 ± 13.2 yr) were acquired using the Digital Light Ophthalmoscope (DLO). 10 subjects had dark fundi and/or high refractive errors, as well as other anterior segment issues. Unique to retinal cameras, the Digital Light Ophthalmoscope (DLO) uses a digital light projector with LED light sources to provide the illumination for both confocal imaging and fixation stimuli. The DLO projects a series of lines across the fundus that is synchronized to the electronic rolling shutter read-out on a 2D CMOS sensor, providing high contrast confocal imaging that is highly customizable through software. Monochromatic 40 deg field images were acquired with alternating red and green LED illumination at 14.3 Hz and overlayed to present a pseudo-color image to the operator in real time. To reduce pupil constriction and patient discomfort while maintaining strong blood absorption, the green illumination was long-pass filtered with a 570 nm filter, and a 1.5mm entrance pupil and time-averaged power of <30 uW was used. ResultsThe DLO provided gradable quality non-mydriatic fundus images in all tested subjects, including those with dark fundi or pupils < 2 mm, as judged by an EyePACS certified grader. The use of long pass filters in the green LED permitted high contrast, non-mydriatic images with illumination wavelengths >570 nm and limited pupil constriction. Retinal vessels at the 4th branch or smaller, as well as neovascularization in diabetic retinopathy, could be seen. Hyperpigmentation was clearly seen both peripherally as bear tracks and centrally at the posterior pole. The aperture width and color balance can be adjusted to provide high contrast and yet relatively uniform and natural color across the image. ConclusionsThe DLO provides confocal color fundus images in real time without the use of short (< 570nm) wavelength light. Despite recruiting an especially challenging population that included dark fundi, small pupils, high refractive errors, and media issues, we achieved a 100% success rate in obtaining gradable images for screening.
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