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Dirk-Uwe Bartsch, Cheryl Arcinue, Feiyan Ma, Lingyun Cheng, William Freeman; Reproducibility of the rtx1 adaptive optics retinal camera. Invest. Ophthalmol. Vis. Sci. 2013;54(15):3431.
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© ARVO (1962-2015); The Authors (2016-present)
To study the reproducibility of the flash-illumination commercially available adaptive optics retinal camera rtx1 (ImagineEyes, Orsay, France) in a group of normal volunteers.
The rtx1 is an adaptive optical fundus camera using flashed, non-coherent flood illumination centered at 850 nm to record a series of 40 images. Each image covers an area of 4° x 4°. The instrument is claimed to have a pixel resolution of 1.6 µm and resolve 250 line pairs per millimeter. The instrument uses a yellow fixation cross to help the subject fixate. The location of the center of fixation cross is stored by the instrument allowing the subject to fixate to the same stimulus location. After approval by the Institutional Review Board we recruited 6 subjects and imaged each subject in two different sessions. We selected 5 regions of interest. One was at the center of the fovea, and the other four regions were centered at 2 degrees from the foveal center in the four principal directions (superior, inferior, nasal and temporal). We selected a measurement area for each image pair that was matching according to vessel landmarks. We used the adaptive optics analysis software from ImagineEyes to measure density and spacing for each image. For statistical analysis we used concordance correlation coefficient (Lin, 1989) with a 95.0% asymptotic confidence interval, and a 95% BCa bootstrap confidence interval using SAS (Cary, NC).
We found that the rtx1 was able to resolve the photoreceptor cone mosaic in the parafoveal area. The instrument was not able to resolve the cone mosaic in the center of the macula. The central 2.5° of the fovea could not be resolved. For density means we found a CCC of 0.767. For spacing means we found a CCC of 0.786.
The rtx1 adaptive optical camera allows reproducible acquisition of the photoreceptor cone mosaic. The resolution limit of the instrument does not allow imaging at the center of the fovea due to the very dense spacing of the photoreceptors. The current software does not allow to exclude blood vessels from the analysis. These two areas might influence overall accuracy and should be excluded in future versions of the software.
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