Visual Psychophysics / Physiological Optics - ARVO

ARVO 2013 Annual Meeting Abstracts by Scientific Section/Group – Visual Psychophysics / Physiological OpticsDirk-Uwe G. Bartsch, Cheryl Arcinue, Feiyan Ma, Lingyun Cheng,William Freeman. Ophthalmology-Shiley Eye Ctr, Univ ofCalifornia-San Diego, La Jolla, CA.Purpose: To study the reproducibility of the flash-illuminationcommercially available adaptive optics retinal camera rtx1(ImagineEyes, Orsay, France) in a group of normal volunteers.Methods: The rtx1 is an adaptive optical fundus camera usingflashed, non-coherent flood illumination centered at 850 nm to recorda series of 40 images. Each image covers an area of 4° x 4°. Theinstrument is claimed to have a pixel resolution of 1.6 µm and resolve250 line pairs per millimeter. The instrument uses a yellow fixationcross to help the subject fixate. The location of the center of fixationcross is stored by the instrument allowing the subject to fixate to thesame stimulus location.After approval by the Institutional Review Board we recruited 6subjects and imaged each subject in two different sessions. Weselected 5 regions of interest. One was at the center of the fovea, andthe other four regions were centered at 2 degrees from the fovealcenter in the four principal directions (superior, inferior, nasal andtemporal). We selected a measurement area for each image pair thatwas matching according to vessel landmarks. We used the adaptiveoptics analysis software from ImagineEyes to measure density andspacing 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).Results: We found that the rtx1 was able to resolve the photoreceptorcone mosaic in the parafoveal area. The instrument was not able toresolve 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 aCCC of 0.767. For spacing means we found a CCC of 0.786.Conclusions: The rtx1 adaptive optical camera allows reproducibleacquisition of the photoreceptor cone mosaic. The resolution limit ofthe instrument does not allow imaging at the center of the fovea dueto the very dense spacing of the photoreceptors. The current softwaredoes not allow to exclude blood vessels from the analysis. These twoareas might influence overall accuracy and should be excluded infuture versions of the software.Commercial Relationships: Dirk-Uwe G. Bartsch, None; CherylArcinue, None; Feiyan Ma, None; Lingyun Cheng, SpinnakerBiosciences (C); William Freeman, OD-OS, Inc. (C)Support: NEI Grants R01EY016323, R01EY007366,R01EY018589, P30EY022589were performed using the following settings: a customized 9-pointpattern, 200 ms stimulus duration, Goldmann III size, 4-2-1 dBstaircase strategy, 10 dB initial brightness, and red cross as thefixation target. The 9 points consisted of a 3x3 upright square latticecentered at the fovea, having a 1.5° angle between the center andevery corner point (Figure). The point sensitivities were recorded.Results: Sensitivities and variances are recorded in the Table.Friedman Test showed no significant differences in the meansensitivities across the 3 sessions in both groups (p>0.7 for both). Theoverall inter-session variances in normal (1.03 ± 0.07) and diseased(2.43 ± 0.51) groups were significantly different (p=0.05, Mann-Whitney Test). The variances of 9 points were significantly differentin both groups (p