Visual Psychophysics / Physiological Optics - ARVO

ARVO 2013 Annual Meeting Abstracts by Scientific Section/Group – Visual Psychophysics / Physiological OpticsWednesday, May 08, 2013 11:00 AM-12:45 PMTCC LL 4/5 Paper SessionProgram #/Board # Range: 4549-4554Organizing Section: Visual Psychophysics / Physiological OpticsProgram Number: 4549Presentation Time: 11:00 AM - 11:15 AMThe impact of Spherical Aberration, Stiles Crawford Apodizationand Spatial Frequency on wavefront-based and subjectiverefractionsRenfeng Xu 1 , Arthur Bradley 1 , Larry N. Thibos 1 , Gildas Marin 2 ,Martha Hernandez 2 . 1 School of Optometry, Indiana University,Bloomington, IN; 2 Essilor International, Paris, France.Purpose: Subjective refraction is independent of pupil size even foreyes with spherical aberration (SA). We tested the popularexplanation that Stiles-Crawford apodization (SCA) biases subjectiverefraction towards the pupil center by attenuating marginal rays.Methods: Aberrometry data were used for objective wavefrontrefractions that indentify the target vergence required to maximizemetrics of image quality for varying levels and signs of SA andapodization, and a range of spatial frequencies (SFs). Subjectiverefractions for a variety of test stimuli were measured with phaseplates that controlled SA levels, and apodization filters that controlledthe Stiles-Crawford effect.Results: In the presence of SA, high SF image quality and subjectiveappearance of best focus are both achieved with a near paraxial focusirrespective of the presence or absence of pupil apodization.Optimum low SF image quality is achieved by focusing moremarginal pupil regions, and thus best focus for low SFs changes withSA levels and apodization. For letter charts used in clinical refraction,optimum retinal image quality is achieved with a sphere lens thatfocuses rays entering the eye 1- 1.5 mm from the pupil center.Conclusions: Clinical subjective refractions are independent of pupilsize because retinal image quality is maximized when rays near thepupil center are preferentially focused, independent of SCA.Removing high spatial frequencies from the visual stimulus makessubjective refractions more dependent on pupil size in the presence ofSA.Commercial Relationships: Renfeng Xu, None; Arthur Bradley,Essilor International (F); Larry N. Thibos, Essilor International (F),Vistakon Inc. (F), Vistakon, Inc. (C), Self (P); Gildas Marin, Essilorinternational (E); Martha Hernandez, Essilor International (E)Support: NIH P30EY019008, Essilor InternationalProgram Number: 4550Presentation Time: 11:15 AM - 11:30 AMImpact of Primary and Secondary Spherical Aberration onPredicted Peripheral Image QualityAmanda C. Kingston 1, 2 , Geunyoung Yoon 2 . 1 BME, University ofRochester, Rochester, NY; 2 Flaum Eye Institute, University ofRochester, Rochester, NY.Purpose: To determine the impact of sign and magnitude of primaryand secondary spherical aberration (SA) on predicted image qualityat retinal eccentricities up to 20°.Methods: An Arizona eye model was implemented in commerciallyavailable optical design software (Zemax Bellevue, WA). Radii ofcurvature, index and thicknesses were used from the model whileaxial length and crystalline lens asphericity were varied to produce aneye with zero defocus and SA. Zernike SA up to ±1.00μm over a6mm diameter was added to the anterior cornea to induce differentsigns and magnitudes of primary and secondary SA. Foveal retinalimage quality with each SA condition was optimized at distance byadjusting defocus. Wavefronts were calculated for an elliptical pupilwith a 6mm long axis, at each retinal eccentricity, using Zemax.Through-focus peripheral image quality, using an image-convolutionbased image quality metric was done with a custom Matlab program.Measured outcomes were retinal image quality, refractive error anddepth of focus (DOF) as a function of retinal eccentricity.Results: For all eccentricities, negative primary SA inducedhyperopic defocus whereas positive primary SA and zero SA inducedmyopic defocus. Peak image quality with zero SA was higher than alleyes with SA, and maintained the same magnitude of myopic shift asprimary SA (0.25D and 1.50D at 10 and 20°, respectively). DOF wasextended with increasing magnitude of primary SA for alleccentricities compared to the zero SA case. Positive secondary SAinduced hyperopic defocus at all eccentricities, whereas negativesecondary SA induced myopic defocus. Secondary SA gives asecondary peak image quality instead of single focus found withprimary SA. This secondary peak is in the hyperopic direction forpositive SA and myopic direction for negative SA. Increasing themagnitude of secondary SA degraded image quality by 26-35% forall eccentricities. Decreasing the magnitude of secondary SA to -0.10μm increased image quality while still maintaining myopicdefocus.Conclusions: Positive primary and negative secondary SA yieldacceptable foveal image quality while maintaining myopic defocus atall eccentricities. Inducing optimal primary and secondary SA of theeye with an advanced ophthalmic lens manipulates the amount ofrefractive defocus and depth of focus in the peripheral retina,potentially providing the ability to control myopia progression.Commercial Relationships: Amanda C. Kingston, Bausch &Lomb (E); Geunyoung Yoon, Bausch & Lomb (F), Johnson &Johnson (F), Allergan (C), Staar Surgical (C), CIBA Vision (F),Acufocus (C)Support: Research to Prevent Blindness (RPB)Program Number: 4551Presentation Time: 11:30 AM - 11:45 AMPeripheral Wavefront Aberrations of Accommodating HumanEyeTao Liu, Larry N. Thibos. School of Optometry, Indiana University,Bloomington, Bloomington, IN.Purpose: Retinal image quality in the peripheral visual field isthought to contribute to visual control of eye growth and myopiaprogression. The contribution of spherical aberration is of particularinterest because accommodation typically causes a sign reversal thatcan have a large impact on accommodative lag and image quality.Thus we aimed to measure spherical aberration in central andperipheral visual field as a function of accommodative demand.Methods: A scanning Shack-Hartmann wavefront aberrometer (Wei& Thibos, 2010 Opt Express 18: 1134) was employed to measureocular aberrations along 37 different lines-of-sight over the central 26degree visual field in 30 seconds. Aberrations were measuredsequentially using light reflected from a small spot produced on thefundus by an incident probe beam that pivoted around the center ofthe eye’s entrance pupil. Scanning mirrors that steered the incidentprobe beam also de-scanned the reflected light into a fixed wavefrontsensor. Accommodation was stimulated over the range 0-6D by anacuity target in a Badal configuration. Target and room illuminationwas reduced to promote pupil dilation. Spherical aberrationcoefficients C40 (primary) and C60 (secondary) for ellipticallyforeshortened pupils (Wei & Thibos, 2010, Optom Vis Sci 87, E767-777) describe ocular wavefront error over a fixed, 6mm circleconcentric with the eye’s pupil.Results: Primary spherical aberration varied significantly in sign andmagnitude over the visual field but always changed in the negative©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.