Visual Psychophysics / Physiological Optics - ARVO

ARVO 2013 Annual Meeting Abstracts by Scientific Section/Group – Visual Psychophysics / Physiological Opticsbuilds on previous experience with multi-wavelength, highsensitivity,imaging double-pass system for the measurement thewide-angle point-spread function of the eye.Commercial Relationships: Onurcan Sahin, None; Harilaos S.Ginis, Universidad de Murcia (P); Guillermo M. Perez, VOPTICA(E); Juan M. Bueno, None; Pablo Artal, AMO (C), Voptica SL (P),Voptica SL (I), AMO (F), Calhoun Vision (F), Calhoun Vision (C),AcuFocus (C)Support: ITN OpAL (PITN-GA-2010-264605), Ministerio deCiencia e Innovación, Spain (grants FIS2010-14926 and CSD2007-00013), Fundación Séneca (Region de Murcia, Spain), grant4524/GERM/06.Program Number: 5546 Poster Board Number: B0056Presentation Time: 8:30 AM - 10:15 AMThe Effect of AOSLO Image Distortion on Metrics of MosaicGeometryRobert F. Cooper 1 , Zachary Harvey 2 , Michael Dubow 3, 4 , Yusufu N.Sulai 5 , Alexander Pinhas 3, 4 , Drew H. Scoles 6 , Nishit Shah 3 , RichardB. Rosen 3 , Alfredo Dubra 2, 7 , Joseph Carroll 2, 8 . 1 BiomedicalEngineering, Marquette University, Milwaukee, WI;2 Ophthalmology, Medical College of Wisconsin, Milwaukee, WI;3 New York Eye and Ear Infirmary, New York, NY; 4 Mount SinaiSchool of Medicine, Mount Sinai Hospital, New York, NY; 5 TheInstitute of Optics, University of Rochester, Rochester, NY;6 Biomedical Engineering, University of Rochester, Rochester, NY;7 Biophysics, Medical College of Wisconsin, Milwaukee, WI; 8 CellBiology, Medical College of Wisconsin, Milwaukee, WI.Purpose: Adaptive Optics Scanning Light Ophthalmoscopes(AOSLOs) permit near diffraction-limited imaging of the humanphotoreceptor mosaic, though intraframe eye movements lead toimage distortion. Here, we explore the impact of these distortions ona number of metrics commonly used to characterize thephotoreceptor mosaic.Methods: We acquired 9 image sequences of the parafoveal conemosaic from 7 subjects on 3 similar AOSLOs. In another subject, weacquired an AOSLO and flood-illuminated AO image sequences ofthe same retinal location. To assess the effect of distortions withinAOSLO images, ten averaged images were produced by registeringagainst different reference frames using a previously describedalgorithm. The images were then registered with the same softwarewhile tracking the distortion applied to each image. Thephotoreceptor coordinates from the reference frame were transformedusing this distortion. Voronoi geometry, cone density, nearestneighbordistance (NND), inter-cell spacing (ICS), and regularityindex (RI) were calculated for each set of images. Repeatability wascalculated to assess the effect of intraframe distortion on thesemetrics.Results: Across the AOSLO images, we analyzed 17,942 cones, 75%of which retained the number of sides in the corresponding Voronoidomains across the 10 images (range 56%-90%). Cone density wasfound to have a repeatability of 1.8% (i.e., the difference between any2 measurements on the same subject would be less than 1.8% for95% of observations). NND and ICS had even better repeatability, at1.4% and 0.95%, respectively. In contrast, the NND RI and ICS RIhad a repeatability of 11% and 31%, respectively. Comparing anAOSLO image set to a flood-illuminated AO image, we foundsimilar repeatability (density: 2.7%, NND: 0.7%, ICS: 0.83%, NNDRI: 8.9%, ICS RI: 20.3%) and 83% of cells had retained Voronoigeometry.Conclusions: Global metrics (density and cell spacing) are minimallyaffected by intraframe distortions, whereas local metrics (regularityindex and Voronoi geometry) are more significantly affected.Intraframe distortion in AO scanning instruments limits themeasurement accuracy of mosaic geometry, thus every effort shouldbe made to choose minimally distorted reference frames.Commercial Relationships: Robert F. Cooper, None; ZacharyHarvey, None; Michael Dubow, None; Yusufu N. Sulai, None;Alexander Pinhas, None; Drew H. Scoles, None; Nishit Shah,None; Richard B. Rosen, Opko-OTI (C), Optos (C), Clarity (C),OD-OS (C), Topcon (R), Zeavision (F), Genetech (F), Optovue (C);Alfredo Dubra, US Patent No: 8,226,236 (P); Joseph Carroll,Imagine Eyes, Inc. (S)Support: RPB, NIH (UL1RR031973, EY017607, EY001931),Foundation Fighting Blindness, Alcon Research Institute, BurroughsWellcome FundProgram Number: 5547 Poster Board Number: B0057Presentation Time: 8:30 AM - 10:15 AMPhotoreceptor imaging with in-the-plane adaptive optics opticalcoherence tomography using toroidal mirrorsZhuolin Liu, Omer P. Kocaoglu, Qiang Wang, Donald T. Miller.School of Optometry, Indiana University, Bloomington, IN.Purpose: Recent technological advances in adaptive optics (AO) andhigh-resolution ophthalmoscopy have resulted in sharper images ofthe cellular retina than previously possible. As part of these ongoingdevelopments, we have re-engineered the Indiana AO-OCT system toimprove imaging performance. In this study, we assessed systemperformance for imaging the 3D structure of photoreceptors.Methods: The 2nd generation Indiana AO-OCT system is based on anovel in-the-plane design of an off-axis ophthalmic AO systemrealized with toroidal mirrors. Unlike conventional designs that relyon all spherical mirrors, the inclusion of toroidal mirrors avoidsaccumulation of system astigmatism and unwanted beamdisplacement at pupil conjugate planes. As part of the new design, theAO system was upgraded with a 97-magnetic-actuator ALPAOwavefront corrector to improve stroke and fidelity, and a Shack-Hartmann wavefront sensor configured with an Andor Neo scientificCMOS camera to improve sensitivity and speed. To assessperformance, volume images of the retina with focus at thephotoreceptor layer were acquired at retinal eccentricities rangingfrom the fovea to 6 degrees in human subjects. Power spectra werecomputed of en face images at different depths in the photoreceptorlayer. Each spectrum was radially averaged to increase signal tonoise.Results: Ray trace analysis of the in-the-plane design predictsdiffraction-limited imaging across the entire 3.6°x3.6° field of viewof the AO-OCT system. Beam displacement of less than the pitch ofthe SHWS lenslet array is also predicted, thus enabling the fullsensitivity of the SHWS to high spatial frequencies. Measured beamdisplacement and wavefront root-mean-square error of the systemconfirmed the theoretical predictions. Cone photoreceptors wereroutinely observed at retinal eccentricities as small as 0.2 degrees.This corresponds to cones narrower than that detected with theprevious Indiana AO-OCT system. Analysis of power spectra at theinner segment / outer segment junction, and posterior tip of the outersegment revealed more energy at high spatial frequencies.Conclusions: The 2nd-generation Indiana AO-OCT system providesa more detailed view of the photoreceptor optical signature than theprevious generation system.Commercial Relationships: Zhuolin Liu, None; Omer P.Kocaoglu, None; Qiang Wang, None; Donald T. Miller, n/a (P)Support: NIH R01EY018339, NIH R01EY014743, NIHP30EY019008Program Number: 5548 Poster Board Number: B0058©2013, Copyright by the Association for Research in Vision and Ophthalmology, Inc., all rights reserved. Go to iovs.org to access the version of record. For permissionto reproduce any abstract, contact the ARVO Office at arvo@arvo.org.