Visual Psychophysics / Physiological Optics - ARVO

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ARVO 2013 Annual Meeting Abstracts by Scientific Section/Group – Visual Psychophysics / Physiological OpticsPresentation Time: 10:30 AM - 12:15 PMThe Effect of Exposure Duration on Visual Acuity for LetterOptotypes Depends On How Visual Acuity is DefinedJ Jason McAnany, Philip R. Nolan, Aimee Beluch. Ophthalmologyand Visual Sciences, University of Illinois at Chicago, Chicago, IL.Purpose: Increasing exposure duration improves visual acuity (VA)for letter optotypes, as defined by the standard logarithm of theminimum angle of resolution (log MAR) scale. This studydetermined the extent to which VA, expressed in terms of retinalfrequency (cycles per degree; cpd), improves with increasingduration after accounting for the object frequency informationmediating performance (cycles per letter; cpl).Methods: Log MAR VA of four visually-normal individuals (ages25 to 35) was measured for a set of tumbling E optotypes presentedon a CRT display for presentation durations ranging from 0.02 to 1.0s. The Es were either unblurred or blurred through convolution withGaussian functions of different widths (σ stim ), which permitted objectfrequency to be derived. Log MAR values were plotted as a functionof log σ stim and fit with the function: MAR = MAR 0 [1 + (σ stim /σ int ) 2 ] 0.5 , where MAR 0 and σ int set the vertical and horizontalpositions of the function, respectively. The object frequenciesmediating VA were derived from MAR 0 and σ int as: cpl =5*MAR 0 *1/(2π*σ int ). The retinal frequencies mediating VA werederived from MAR 0 and cpl as: cpd = 12*cpl/ MAR 0 .Results: Log MAR for the unblurred E decreased (VA improved)significantly (p < 0.05) by a factor of 1.6 as duration was increasedfrom 0.02 to 0.50 s, but log MAR was constant for durations longerthan approximately 0.50 s. These findings are consistent withprevious reports. Increasing the exposure duration had similar effectson log cpl, a relationship that has not been reported previously. Thatis, from 0.02 to 0.50 s, cpl decreased significantly (p < 0.05) by afactor of approximately 1.6, and was constant for longer durations.However, VA expressed in cpd was independent of exposureduration. This constancy is due to the offsetting effects of thedecrease in letter size (increase in cpd) and the decrease in cpl(decrease in cpd), as indicated in the definition of retinal frequency.Conclusions: The extent to which VA for broadband optotypesimproves with increasing exposure duration depends on how VA isdefined. If it is assumed that object frequency is independent ofduration (i.e. the log MAR scale), then VA improves as duration isincreased up to approximately 0.50 s. However, if both size andobject frequency are included in the definition of VA (i.e. cpd), thenVA is approximately independent of duration.Commercial Relationships: J Jason McAnany, None; Philip R.Nolan, None; Aimee Beluch, NoneSupport: NIH research grant R00EY019510 (JM), NIH core grantP30EY001792, and an unrestricted departmental grant from Researchto Prevent Blindness.Program Number: 580 Poster Board Number: C0191Presentation Time: 10:30 AM - 12:15 PMAssessing the Quality of Functional Vision through AdSpecsNadine Solaka 1 , Hilary Gaiser 1 , Joshua Silver 2 , Bruce Moore 1 . 1 NewEngland College of Optometry, Boston, MA; 2 Center for Vision inthe Developing World, Oxford University, Oxford, United Kingdom.Purpose: According to the RESC Studies, at least 10% of children inthe developing world could benefit from refractive correction. Lackof professional eyecare limits access to refractive correction.Adjustable glasses (AdSpecs) both measure and correct refractiveerror. A previously published study showed that AdSpecs provideclear vision when adjusted by myopic children. However, it remaineduncertain whether this complex lens system may adversely effectvisual function, especially at near. The purpose of this study was toassess near visual function through AdSpecs.Methods: 30 myopic adults 21-41 years of age were recruited fromNew England College of Optometry. Near VA was measured in M-units using a Good-Lite (#251000) near card at 40 cm. Contrastsensitivity (CS) was measured using a Mars Test (mars perceptrix) at50 cm. Lateral and vertical phoria were measured with ModifiedThorington at 40 cm. All tests were done in down gaze (45° fromprimary gaze) with both AdSpecs and habitual correction (HC).Inclusion criteria were: Hyperopia +1.50 to +4.50 D, Myopia -0.75 to-6.00 D, Astigmatism
ARVO 2013 Annual Meeting Abstracts by Scientific Section/Group – Visual Psychophysics / Physiological Opticsfragment-perception was distinct from the topography of the P2elicited by probes during fragment perception, suggesting that neuralprocessing of probes differed as a function of perceptual state. Twosource localization algorithms estimated the neural generator of thedifference positivity to lie in the lateral occipital cortex (LOC), aregion associated with object perception.Conclusions: These data suggest that objects attract attention andmodulate the processing of individual elements occurring within theirboundaries, perhaps reflecting the perceptual binding of the elementsinto a unified object. Importantly, these effects were observed whenthe perceived "object" in this case emerged as a function of thefluctuating perceptual state of the viewer.Commercial Relationships: Anastasia V. Flevaris, None;Antigona Martinez, None; Steven Hillyard, NoneSupport: T32 MH 020002-11A1Program Number: 582 Poster Board Number: C0193Presentation Time: 10:30 AM - 12:15 PMDigital precise remote near visual acuity evaluation using mobiledevicesOren Yehezkel, Anna Sterkin, Maria Lev, Uri Polat. Ucansi Inc., NewYork, NY.Purpose: Our aim was to develop a tool for precise remote selfassessmentof near visual acuity in order to accurately and remotelyestimate the functional reading acuity.Methods: We used an application by Ucansi Inc., developed for iOSbasedmobile devices (iPhone, iPad, iPod), based on the technologytested both on mobile devices and PCs (electronic visual acuity,eVA). Here we present part of the data, collected on 73 volunteersthat were tested on iPhone 4, operating the application by themselves.The minimal measurable acuity is -0.18 logMAR, as determined bythe pixel size of 0.078 mm. The stimuli were matrices composed of25 letters "E" (5×5), each with a randomly chosen orientation out of 4possibilities (left, right, up or down). Two variations of inter-letterspacing within the matrix were used (0.4 and 1 letter size). The taskwas to report the orientation of the central letter. The evaluation wasperformed using a staircase measuring the minimal detectable targetsize. For each staircase, the duration of target presentation (rangingbetween 240 to 30 msec) and the inter-letter spacing were changed.The results were compared to the standard clinical near visual acuitychart (ETDRS chart-based visual acuity, cVA) and to the requiredreading addition (measured using the fused cross-cylinder test, FCC).Results: There was a significant correlation between the eVA and thecVA. Best correlation was found between monocular eVA and cVA(R=0.85, p
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