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Lucie Sawides, Kaitlyn Anne Sapoznik, Alberto De Castro, Brittany Walker, Thomas Gast, Ann E Elsner, Stephen A Burns; Localized defects in foveal cone mosaic imaged in diabetes with AOSLO. Invest. Ophthalmol. Vis. Sci. 2016;57(12):5098.
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© ARVO (1962-2015); The Authors (2016-present)
Adaptive optics (AO) retinal imaging allows high resolution investigation of the impact of disease on the eye. While changes in retinal vasculature in diabetic patients are widespread, changes to the number of cones are not consistently found. To further investigate the impact of diabetes on cone photoreceptors we examined cone packing in the central 4 degrees of the retina.
46 diabetic patients (53.5±12.9 yr) were imaged with the Indiana AOSLO. Follow-up imaging sessions were available with intervals from 4 months to 3 years for eight of the patients. Normal healthy subjects were drawn from a large pool imaged in the lab. All subjects had acuities of 20/40 or better. Measurements of foveal cones and retinal capillaries were obtained for a region of 4.0x3.6 deg. Two imaging beams (820 and 785 nm) were used to generate confocal and multiply scattered light images simultaneously using a centered 2 Airy disk and an offset 10 Airy disk diameter confocal aperture respectively. After removing the impact of eye movements and aligning individual frames, montages of average images, generated using an automated algorithm combining Matlab, i2k Retina and Adobe Photoshop, were examined for packing regularity.
Unlike in the normal subjects, cone mosaic images from diabetics often showed multiple dark retinal regions where cones were not visible. When compared to the capillary images, these dark regions could be spatially related to shadowing due to changes to the overlying retina, including vascular remodeling or localized edema. However, in 11 of the 46 diabetics, there were localized defects in the foveal cone mosaic that did not directly correspond to overlying vasculature changes or blood vessel shadows. These defects, stable over time, range in size from 10x10 to 75x30µm and were visualized as sharp edge areas of contiguous dark cones largely preserving the cone mosaic. Figure 1 compares two cone images from the same region imaged with a 4 month interval, with darkened cones and a sharp border with bright cones on the edge.
Foveal cone mosaic can show evidence of localized defects that persist over time and may correspond to either missing or non-reflecting photoreceptors. While these changes are not evident in all diabetics, they may represent regions of outer retinal edema.
This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.
Figure1. Localized defects in the foveal cone mosaic for one diabetic patient imaged at the initial session and 4months later.
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