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Akio Oishi, Jiro Hidaka, Nagahisa Yoshimura; Quantification of the image obtained with wide-field scanning ophthalmoscope.. Invest. Ophthalmol. Vis. Sci. 2014;55(13):1601.
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© ARVO (1962-2015); The Authors (2016-present)
To quantify the angle of view, the magnification rate, and the quality of images acquired with Optos 200Tx.
Vertical and horizontal angular scales were placed on the inner surface of a fluid-filled and gas-filled model eye. We obtained fundus images with Optos 200Tx and recorded the maximal scale imaged in each direction. We measured the length of the scale bar at each angle and calculated the magnification rate. We also measured contrast between scale bars and intervals between scale bars.
The fundus image obtained with Optos 200Tx covered 96, 101,76, and 102 degree in up, right, down, and left-ward, respectively. When we rotated the model eye, we could obtain maximum of 110, 122, 91, and 122 degree in each direction, respectively. The quantitative measurement showed that the overall image is stretched to horizontal direction in 1.12 folds and the peripheral part of the image is magnified exponentially. The magnification rate compared to the posterior pole was 1.2 times at 60 degree and 1.5 times at 95 degree in horizontal direction. The rate was 1.6 times at 60 degree in downward: unequal in horizontal and vertical direction. Image quality was also different depending on the location; the contrast was the best in left part and was worse in inferior or superior part.
Optos 200Tx can obtain approximately up to 120 degree image especially in horizontal direction. Although the device must be useful in evaluating peripheral retinal abnormalities, it should be noted that the most peripheral part of the image is significantly and unequally magnified. In addition, contrast is not equal in each position. The present data would serve as a guide to correct the peripheral magnification in future studies.
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