Visual Psychophysics / Physiological Optics - ARVO

ARVO 2013 Annual Meeting Abstracts by Scientific Section/Group – Visual Psychophysics / Physiological OpticsPresentation Time: 8:30 AM - 10:15 AMEvaluation of a Dual-Conjugate Adaptive Optics ClinicalPrototype for Retinal ImagingZoran Popovic 1 , Jörgen Thaung 1 , Bengt Svensson 2 , Mette Owner-Petersen 1 . 1 Department of Ophthalmology, University ofGothenburg, Mölndal, Sweden; 2 Exomed AB, Sollentuna, Sweden.Purpose: To investigate the applicability of a new dual-conjugateadaptive optics clinical prototype for wide-field high-resolutionadaptive optics retinal imaging in healthy volunteers and patientswith early stages of retinal disease.Methods: A new design of a compact dual-conjugate adaptive opticsclinical prototype has been built and used to image healthy volunteersand patients with early stages of retinal disease such as age-relatedmacular degeneration (AMD) and diabetic retinopathy (DR).The clinical prototype, based on the concept of dual-conjugateadaptive optics, employs five spatially separated retinal probebeacons, two magnetic deformable mirrors (DM) (ALPAO,Grenoble, France), and a multi-channel Shack-Hartmann wavefrontsensor.Monochromatic aberrations are measured and corrected over a 6 mmpupil. The five probe beacons are generated using light at awavelength of 830±10 nm from a superluminescent diode (Superlum,Cork, Ireland). A 52 actuator DM positioned in a plane conjugate tothe pupil of the eye will apply an identical correction for all fieldpointsin the field of view (FOV). A 97 actuator DM positioned in aplane conjugated to a plane inside the eye will contribute withpartially individual corrections for the five angular directions andthus compensate for non-uniform (anisoplanatic) or field-dependentaberrations. Imaging is performed over a 7x7 deg FOV using aspectrally filtered Xenon flash at a wavelength of 575±10 nm.Results: The dual-conjugate adaptive optics clinical prototypefeatures a 7x7 degree FOV and allows retinal features down to 2 μmto be resolved. A narrow depth of field of approximately 9 µm in theretina enables tomographic imaging of separate retinal layers, such asthe cone photoreceptor layer deep within the retina in AMD patients,and superficial retinal capillary layers in DR patients.Conclusions: High resolution adaptive optics retinal imaging hasenabled the vision research community to gain deeper insight into thedevelopment and progression of retinal diseases. We believe that thedual-conjugate adaptive optics clinical prototype has a futurepotential for clinical imaging with an impact particularly importantfor early diagnosis of retinal diseases, follow-up of treatment effects,and follow-up of disease progression.Commercial Relationships: Zoran Popovic, US7639369 (P),PCT/EP2012/069620 (P), EP12165365 (P); Jörgen Thaung,US7639369 (P), PCT/EP2012/069620 (P), EP12165365 (P); BengtSvensson, Exomed AB (E), PCT/EP2012/069620 (P), EP12165365(P); Mette Owner-Petersen, US7639369 (P), PCT/EP2012/069620(P), EP12165365 (P)Support: Marcus and Amalia Wallenberg's Memorial Fund GrantMAW 2009.0053, Vinnova Grant 2010-00518Program Number: 5549 Poster Board Number: B0059Presentation Time: 8:30 AM - 10:15 AMAO-OCT Retinal Imaging with 163-Segment Deformable MirrorSusanna C. Finn 1 , Cherry Greiner 1 , Nathan Doble 1 , Robert J.Zawadzki 2 , John S. Werner 2 , Stacey S. Choi 1 . 1 Vision Science, NewEngland College of Optometry, Boston, MA; 2 Ophthalmology &Vision Science, University of California Davis, Davis, CA.Purpose: Adaptive Optics (AO) has enabled vision scientists todirectly image single retinal cells in vivo. We have constructed anAO Fourier-domain Optical Coherence Tomography (AO-FD-OCT)system utilizing a high segment count microelectromechanicalsystems (MEMS) deformable mirror (DM). This DM provides muchhigher spatial correction over a 7.5mm dilated pupil (Doble et al.Applied Optics 2007), providing diffraction-limited imaging. Wedescribe retinal imaging results obtained on a range of humansubjects.Methods: An AO-FD-OCT was designed and constructed at the NewEngland College of Optometry. The AO-OCT system acquires B-scans made up of 600 A-scans at a frame rate of 60 Hz. A Superlumbroadband superluminescent diode (SLD) light source is used with acentral wavelength of 860nm and a full bandwidth of 135nm.Imaging data are post-processed and analyzed with custom Matlabsoftware. The AO system consists of a Hartmann-Shack wavefrontsensor and a 163-segment, 489-actuator Iris AO MEMS DM. TheAO-OCT is designed for a 7.5mm pupil, with 13 discrete mirrorsegments across the pupil diameter.Retinal images were obtained on normal human subjects at 4 and 10degrees in the nasal retina. The scan size for each B-scan was 0.5°,corresponding to approximately 150µm at the retina.Results: Distinct retinal layers were visible from the nerve fiberlayer, to the inner and outer photoreceptor segments, through to theretinal pigment epithelium. Moreover, individual cone photoreceptorswere clearly visible in images at 4 and 10 degrees eccentricity. Thelateral spacing of the cones was measured to be 6.4±1.5 microns at 4°nasal, and 10.4±3.8 microns at 10°. The inner segment length of thecones was found to be 32.9±5.7 microns at 4°, and 24.5±3.0 micronsat 10°. The outer segment length was correspondingly found to be26.2±1.9 microns at 4°, and 27.8±1.4 microns at 10°. These resultsare in good agreement with histology.Conclusions: The combination of AO with the use of a highersegment MEMS DM with established OCT technology has enabledus to resolve fine retinal structure unseen with conventional OCTtechnologies and promises to be highly valuable in the study ofretinal disease and injury.Commercial Relationships: Susanna C. Finn, None; CherryGreiner, None; Nathan Doble, Iris AO Inc (I); Robert J.Zawadzki, None; John S. Werner, None; Stacey S. Choi, NoneSupport: DoD Grant W81XWH-10-1-0738Program Number: 5550 Poster Board Number: B0060Presentation Time: 8:30 AM - 10:15 AMUse of multiple metrics to describe the parafoveal cone mosaicMarco Lombardo 1 , Sebastiano Serrao 1 , Pietro Ducoli 1 , GiuseppeLombardo 2, 3 . 1 Fondazione GB Bietti IRCCS, Rome, Italy; 2 CNR-IPCF Unit of Support Cosenza, Rende, Italy; 3 Vision Engineering,Rome, Italy.Purpose: To investigate the distribution of cone density and spacingas well as the preferred packing arrangement of the cone mosaic as afunction of retinal eccentricity.Methods: A flood-illumination adaptive optics retinal camera wasused to obtain images of the parafoveal cone mosaic in nineteenhealthy volunteers. Cone density and spacing were estimated for eachsubject using a sampling window of 80 x 80 pixels, at 250-, 450-,650- and 1100-um eccentricities from the fovea along the nasal andtemporal retina of both eyes. The inter-subject and intra-subjectvariation of cone density and spacing were calculated via Coefficientof Variation (CoV). Cone packing arrangement was assessed usingVoronoi analysis; calculations were done over 1024x128 pixelsimage sections of the cone mosaic across the horizontal meridianfrom 200- to 1050-um eccentricities.Results: The inter-subject variation of parafoveal cone densityranged between 10% and 15% (P