Visual Psychophysics / Physiological Optics - ARVO

ARVO 2013 Annual Meeting Abstracts by Scientific Section/Group – Visual Psychophysics / Physiological OpticsWilliam S. Tuten 1 , Wolf M. Harmening 2 , Lawrence C. Sincich 3 ,Austin Roorda 2 . 1 Vision Science, University of California, Berkeley,Berkeley, CA; 2 School of Optometry, University of California,Berkeley, Berkeley, CA; 3 Vision Sciences, University of Alabama atBirmingham, Birmingham, AL.Purpose: To distinguish L-cones from M- and S-conespsychophysically in humans using an adaptive optics scanning laserophthalmoscope (AOSLO).Methods: We used a multi-wavelength AOSLO to measure visualsensitivity to cone-sized stimuli under L-cone isolating conditions intwo subjects with normal color vision. Increment thresholds weremeasured at 1.5° eccentricity, and stimulus delivery to targeted coneswas achieved using high-speed retinal eye tracking. An image-basedmeasure of transverse chromatic aberration (TCA) was obtained andused to ensure repeated stimulation of the cone of interest. The teststimulus (λ = 711 nm) was a square which subtended 27 seconds ofarc (= 2.2 microns) on the retina. The background was comprised ofdim infrared light from the imaging beam, light leaking through theacousto-optic modulator in the red stimulus channel, and an external488 nm LED source viewed through a beam splitter. The luminancesof the red and blue backgrounds were 2.5 and 50 cd/m2, respectively.Converting these luminances to cone contrasts, an L- versus M-conesensitivity ratio of 24-to-1 was expected. Stimulus intensity of the redbeam was controlled via 10-bit modulation and expressed as arbitraryunits (au) ranging from zero to 1. Thus, for L-cone thresholds greaterthan 0.042 au, M- and S-cone thresholds would be predicted to liebeyond the upper modulation limit of the stimulus beam (i.e., >1.0au).Results: Thresholds were measured for 88 cones in the two subjects.The stimulus was readily visible in one group of cones (n = 59;threshold = 0.55 ± 0.14SD au), and these were classified as candidateL-cones. A second group of cones (n = 18) had thresholds above 1.0au, with even the brightest stimulus being not visible. In these cones,threshold values were normal when tested under achromaticconditions, ruling out underlying dysfunction. In the remainingcones, classification was ambiguous (n = 11). Finally, there weremultiple sites in each subject where thresholds from neighboringcones yielded different spectral identities, supporting the notion thatthe spatial accuracy of our psychophysical apparatus is on the orderof a single cone.Conclusions: With combined retinal eye tracking, high-orderaberration correction, and TCA compensation, AOSLO can be usedto identify the spectral class of single cones in vivo with apsychophysical approach.Commercial Relationships: William S. Tuten, None; Wolf M.Harmening, None; Lawrence C. Sincich, None; Austin Roorda,US Patent #6890076 (P), US Patent #7118216 (P), UC Berkeley (P)Support: EY007043; Irvin M. Borish-Essilor Ezell Fellowship; DFGHa 5323/2-1; EY021642; EY019566; Eyesight Foundation ofAlabama; EY014375Program Number: 3706Presentation Time: 3:00 PM - 3:15 PMS-cone Electroretinograms in Old and New World PrimatesRecorded Using Two MethodsJames A. Kuchenbecker, Scott H. Greenwald, Maureen Neitz, JayNeitz. Ophthalmology, University of Washington, Seattle, WA.Purpose: Using the exchange of two lights that lie along a tritan linemakes it possible to isolate pure S-cone electroretinogram (ERG)signals. Here, we compare the pure S-cone ERG using silentsubstitution with a method in which “S-cone ERGs” are obtained toshort wavelength flashes in the presence of intense long wavelengthadaptation. Results were compared in an Old World (OW) primate(baboon) and a New World (NW) primate (squirrel monkey) toevaluate the possibility of differences in S-cone circuitry between thetwo primate groups that have been proposed to explain reportedneuroanatomical differences.Methods: An LED Ganzfeld system was used (Q450; RolandConsult, modified by replacing 450 with a 420 nm LED). A tritanpair of lights was alternated at 1 Hz with a 50% duty cycle. A tritanpair that completely isolated S-cone responses for each individualanimal was found by making small adjustments to the relativeintensities of the two lights while taking advantage of the strikingdifferences in the temporal characters of L/M vs. S-cone ERGsignals. For comparison, “S-cone ERGS” were recorded in responseto the 420 nm LED in the presence of steady adaption from an amberLED (~590 nm peak).Results: Compared to L/M, S-cone ERGs have very distinct temporalcharacteristics. The component waves also have strikingly differentrelative amplitudes including a much smaller a-wave and absent d-wave which can be explained by the absence of S-cone specific offbipolarcells in primates. In comparison to the pure S-cone ERGsobtained with silent substitution, long wavelength adaptation canreduce but does not eliminate L/M contamination.Conclusions: Using silent substitution we recorded pure S-coneERGs to investigate differences between S-cone and L/M conemediated signals very early in the visual pathway. The temporal peakof both the S-cone a- and b-wave is slower indicating thesluggishness of S-cone temporal responses observed in humanpsychophysics has its origins in the outer retina and, at least, partly inthe cones themselves. The robust off-bipolar cells signals in both thea- and d-waves elicited by L/M cone stimulation are absent in thepure S-cone ERG with no evidence for the species differencespredicted from the anatomy in which off-midget bipolars have beenproposed to contact S-cones in OW but not NW primates.Commercial Relationships: James A. Kuchenbecker, None; ScottH. Greenwald, None; Maureen Neitz, Genzyme (F), Alcon (F),Alcon (P); Jay Neitz, Alcon (F), Alcon (P)Program Number: 3707Presentation Time: 3:15 PM - 3:30 PMAge-related decline in chromatic-spatial sensitivityElise W. Dees 1, 2 , Stuart J. Gilson 1 , Rigmor C. Baraas 1 . 1 Optometry& Visual Science, Buskerud University College, Kongsberg,Norway; 2 Mathematical Sciences & Technology, NorwegianUniversity of Life Sciences, Ås, Norway.Purpose: The aim was to investigate the variation in chromaticcontrast sensitivity to low spatial frequencies for observers withvarying degrees of color discrimination at different age decades.Methods: Twenty six normal trichromatic subjects (17 females and 9males, aged 20-71 years), 2 female carriers of protan color visiondeficiencies (aged 20-39) and 6 female carriers of deutan color visiondeficiencies (aged 20-59) were included in the study. All observerswere healthy with no known ocular abnormalities. They were testedwith a battery of color vision tests and their statuses of either anormal trichromat or a carrier were confirmed with genetic analysisof the genes encoding L- and M-pigments. The observers werecorrected to best logMar visual acuity and viewed the stimulusmonocularly at a distance of either 114.6 cm (0.3-3.0 c/deg) or 229.2cm (4.0-6.0 c/deg). The stimulus was a Gabor patch with apseudoisochromatic design. The chromatic contrast was varied alongeither the L- or M-cone axis in the CIE 1931 chromaticity diagram.The observers were tested with 9-16 different spatial frequenciesfrom 0.3-3.0 c/deg in all observers, and up to 6.0 c/deg in some.Results: The sensitivity to chromatic spatial patterns declined withage. Subjects aged 50 years and older had significantly lower©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. 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