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Matthew S Muller, Ann E Elsner, Thomas Gast, Allen Ingling, Jeffrey L Clendenon; Multi-mode confocal color fundus imaging using a Digital Light Ophthalmoscope. Invest. Ophthalmol. Vis. Sci. 2016;57(12):1700.
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© ARVO (1962-2015); The Authors (2016-present)
To provide autofluorescence, confocal pseudo-color, and high magnification imaging of the fundus using modular arrangements of the Digital Light Ophthalmoscope (DLO). To improve the color balance of high contrast pseudo-color fundus images to provide a more natural color balance suitable for image review and grading.
The DLO was used in 3 modes by experienced operators in a laboratory setting: non-mydriatic color fundus imaging, mydriatic imaging of autofluorescence, and mydriatic imaging at high magnification. Retinal images of 38 deg were acquired at 14.3 Hz with alternating red (630 nm) and orange (580 nm) LED illumination. A series of 16-bit images were made by power-law scaling the red and orange images in 0.1 increments and combining them in the red and green color channels of an RGB image, respectively. Two experienced graders selected the most natural color balance by comparing the scaled pseudo-color images. Autofluorescence 38 deg field images were acquired at 14.3 Hz on 28 dilated subjects, aged 60 ± 11 yrs, including 2-3 with age-related macular degeneration and ocular melanoma, using 90 uW time-averaged excitation illumination at 535-555 nm. Autofluorescence was detected using a 565 nm dichroic beamsplitter and 580 nm long pass emission filter. Direct backscatter was simultaneously detected by a second identical CMOS camera to perform image registration. High magnification imaging over a 4 deg field was performed at 16.9 Hz on 3 dilated subjects, aged 32 ± 2 yrs, using 20 uW time-averaged power at the cornea using red or orange illumination.
Pseudo-color images appeared at exceptionally high contrast. Among the autofluorescence images, drusen, hypofluorescence and hyperfluorescence associated with age-related macular degeneration were clearly visible. With the high magnification images, cones and capillaries were visible in both red and orange illumination. The orange and red images required gamma values of 0.7 and 0.8-1.0, and scaling coefficients of 1 and 0.9, respectively for natural color balance and brightness.
The relatively simple and compact hardware requirements for DLO imaging permit a variety of imaging modes currently achieved by costlier scanning laser ophthalmoscope technology. By rescaling the red and green channel images, realistic pseudo-color images of dark fundi can be created for reading and analysis.
This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.
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