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Masaki Tanito, Simone Pajaro, Andrea De Giusti; Quantification of color information in images obtained by a novel 360-degree gonioscope. Invest. Ophthalmol. Vis. Sci. 2016;57(12):5118.
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© ARVO (1962-2015); The Authors (2016-present)
Gonioscopy is essential to make a correct diagnosis of glaucoma, however, requires an examiner’s skill and only provide subjective information. Assessment of anterior chamber angle by using currently available modalities including ultrasound biomicroscopy or anterior segment optical coherence tomography that enable quantitation of the angle structure are achromatic technique and therefore don’t provide any chromatic information. Recently developed gonioscopic device (Gonioscope NGS-1, NIDEK Technologies Srl, Italy) was able to automatically acquire true color images of the irido-corneal angle structures and combine them in a 360-degree picture of the angle (Tanassi C, et al., Abstract Number 4975, ARVO 2015). In this study, image analyses were performed in the pictures obtained by using NGS-1 to quantify the color information of the angle.
The NGS-1 system detects the irido-corneal angle using a prism with a soft contact to the corneal surface. The prism has 16 mirrored facets, each of them projecting white light to a single portion of the irido-corneal angle (about 4x4 mm2). A rotating 1.3 megapixel camera element scans all the facets to capture 5 images, at different focus depth, for each of the 16 sectors in less than 2 seconds. On an each selected image from 16 sectors, a region of interest (ROI) was manually defined in the area of trabecular meshwork on the computer screen. From each ROI, pixels’ color information was extracted in 3 color spaces (e.g., RGB, XYZ, and Lab), and several indices were calculated.
By image analyses, 9 histograms and 36 single values (mean, standard deviation, minimum and maximum values for each color channels) were successfully obtained from a set of 16-images. Plot of the mean channel values of each portion on the TSNIT graph showed unique distributions among a, b, and L channels, while 3 channels of RBG or XYZ color spaces largely overlapped each other.
The color information of trabecular meshwork was analyzed in the 360-degree irido-corneal angle images. By this initial image analysis, the Lab color space seems to contain the most information, while the RGB and the XYZ mimic the L channel of the Lab color space. The established method can be applied to understand color/pigment variations among specific directions in normal and glaucomatous eyes.
This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.
The graph represents the Mean L values among the 16 images.
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