Visual Psychophysics / Physiological Optics - ARVO

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ARVO 2013 Annual Meeting Abstracts by Scientific Section/Group – Visual Psychophysics / Physiological Opticseach retinal location could be measured. As an example, for subjectN1, the projection of the cone pointing at the pupil plane from allretinal locations fell within an area of 0.25mm in diameter, locatedslightly nasally (0.15mm) from the pupil center along the horizontalmeridian. The other subjects showed similar nasal bias in alignmentwith respect to the pupil center.Our disarray is smaller than that reported by previous studies(Roorda, JOV, 2002) possibly due to choosing areas that did notinclude retinal blood vessels.Conclusions: For normal subjects, our results are in agreement withprevious reports (both psychophysical and imaging studies) that thedisarray of the photoreceptors is very small; which is to optimize theefficiency of light capture within the photoreceptors. In diseasedeyes, larger variations in cone disarray were reported (Choi et al,IOVS 2008).Commercial Relationships: Nathan Doble, Iris AO Inc (I);Rebecca Kivlin, None; Johanan L. Codona, None; Simone Li,None; Stacey S. Choi, NoneSupport: EY020901Program Number: 3429 Poster Board Number: C0150Presentation Time: 11:00 AM - 12:45 PMThe role of defocus on photoreceptor light coupling analyzedwith a waveguide-based retinal simulatorBrian Vohnsen 1 , Diego Rativa Millan 2 , Carmen Vela 1 , BenjaminLochocki 1 , Philip B. Kruger 3 . 1 School of Physics, University CollegeDublin, Dublin, Ireland; 2 Pós-Graduação em Engenharia de Sistemas(PPGES), Universidade de Pernambuco, Recife, Brazil; 3 College ofOptometry, State University of New York, New York, NY.Purpose: Obliqueness of light at the retina diminishes the visualresponse as a consequence of the Stiles-Crawford effect caused byphotoreceptor waveguiding. The aim of this study is to analyze thesensitivity to defocus under waveguide conditions that resemble thoseof the human eye retina using a retinal simulator consisting of anarray of photonic-crystal waveguides.Methods: A liquid-filled photonic crystal fibre array has been used tosimulate waveguiding by retinal photoreceptors and the total fractionof coupled light has been measured. Defocus is generated with aBadal-system and monitored simultaneously with a Hartmann-Shackwavefront sensor. Measurements are performed both at 633 nm andat 543 nm wavelength to study a possible chromatic impact. Theresults are compared with those of an analytical waveguide modeland Zemax-based eye models.Results: Measurements show that the fraction of coupled light poweris sensitive to defocus as expected due to the wavefront curvature atthe entrance facet of the waveguides. This is in agreement with thenumerical models suggesting a possible role of light power foraccommodation and emmetropization of the eye.Conclusions: We found that a photonic crystal fibre array is asuitable experimental tool to analyze the role of defocus and moregenerally aberrations and their possible role on vision and effectiveretinal images. The fraction of light that couples to waveguide modesmay provide a clue for accommodation and emmetropization of theeye. The sign of defocus is not determined but may relate to thechromatic difference for a finite bandwidth or to photoreceptordisarray though also other aberrations and other factors can provideaccommodative clues.Commercial Relationships: Brian Vohnsen, None; Diego RativaMillan, None; Carmen Vela, None; Benjamin Lochocki, None;Philip B. Kruger, NoneSupport: Science Foundation Ireland grants 07/SK/B1239a and08/IN.1/B2053Program Number: 3430 Poster Board Number: C0151Presentation Time: 11:00 AM - 12:45 PMMeasurement of the Photoreceptor Pointing in the Living ChickEyeMaria Walker, Rebecca Kivlin, Nathan Doble. Vision Science, NewEngland College of Optometry, Boston, MA.Purpose: The chick retina is a widely used animal model in the studyof eye growth, in particular for the study of emmetropization andmyopia. Like most eyes, the ability to image the fine retinal structureis degraded by the aberrations in the lens and cornea. In previouswork, we showed in-vivo images of individual chick photoreceptorstaken with an adaptive optics (AO) fundus camera (Headington et al.Current Eye Research, 2011). Here we utilize this imaging capabilityto examine the individual cone directionality of the chickphotoreceptors.Methods: Two White Leghorn chickens (Gallus gallus domesticus)(age 30d, approx. 650g) were anesthetized with a combination ofKetamine/Xylazine and dilated with Vecuronium Bromidesuspension prior to imaging. The AO fundus camera at the NewEngland College of Optometry was modified in order to image thesmaller 3mm pupil of the chick. Translating the entrance pupilposition of the imaging beam (650nm) allowed for the measurementof the individual cone pointing. Thirteen entrance pupil positionswere tested to obtain 1-degree FOV retinal images; four retinalimages were registered for each position. Upon compensating for thevariation in incident light intensity due to light delivery optics, acentroiding algorithm was used to determine the directionality ofindividual cones.Results: Upon projection of the cone pointing toward the pupil plane,the degree of disarray was found to be slightly larger than that foundin the human eye. Interestingly, our initial results show an ellipticalpointing pattern in the pupil plane with major and minor axes of 0.5and 0.2 mm respectively. The major axis was horizontal and thecenter of the pattern lay on average 0.5 mm from the pupil center.Conclusions: Similar to the human eye, the chick photoreceptordisarray is small, implying that the receptors are aligned to maximizethe signal coming through the center of the pupil aperture.Commercial Relationships: Maria Walker, None; Rebecca Kivlin,None; Nathan Doble, Iris AO Inc (I)Support: NH Grant EY020901Program Number: 3431 Poster Board Number: C0152Presentation Time: 11:00 AM - 12:45 PMReproducibility of the rtx1 adaptive optics retinal camera©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.
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
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