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Stephen A. Burns, Weiyao Zou, Xiaofeng Qi, Zhangyi Zhong, Gang Huang; Rapid Cone AOSLO Imaging And Analysis. Invest. Ophthalmol. Vis. Sci. 2011;52(14):3195.
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To develop AOSLO techniques for obtaining and analyzing photorecptor images. In the current work we test a new algorithm which while less specific than complete counting rapidly estimates cone spacing properties and also generates a lower bound estimate of AO control accuracy.
Images are acquired with the Indiana dual-DM AOSLO which includes computer controlled steering mirrors that can place the AO within a 30 degree field of view. AOSLO imaging is initiated while the subject is fixating, and approximately 2 seconds of data is collected at 30 frames per second. The AO imaging field is then displaced according to a pre-programmed pattern, and another image acquisition is initiated. Locations and system parameters are saved to a database. Off-line, images for each location are averaged and stitched. The composite image is then analyzed using a sweeping window of 200 microns. Within each window, the brightest pixels are automatically selected. These pixels typically represent bright cones. A 25-50 micron region around each bright region is then extracted, and the subregions averaged using a shift-add approach, providing an image of an average bright cone.
Cone image mosaics along all four principal meridia from the fovea to 10 degrees within a one hour session. Image analysis produces excellent estimates of the hexagonal structure of the cone array. Figure 1 shows results from 2, 1.4, 0.8 and 0 degrees (averaged within 120 micron wide regions). The width of the central island represents a convolution of the point spread function of the AO system with the average cone within that region. At the fovea the cones are small placing an upper bound on the width of the psf. In the example the half-width was 2.6 microns. The nearest neighbors and second nearest
The automatic estimation of average cone neighborhoods provides a quick estimates of the normality of cone packing in subjects. While, more detailed analysis techniques will be needed to examine local pathological changes the new approach allows rapid evaluation of the retina and AO control.
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