Visual Psychophysics / Physiological Optics - ARVO

ARVO 2013 Annual Meeting Abstracts by Scientific Section/Group – Visual Psychophysics / Physiological Opticsobject was 13.95 seconds. Both patients were given a SystemUsability Scale (SUS) test. Patients RS-2 and NM gave the OLFSsystem a score of 87.5% and 67.5%, respectively. A 100% scoresymbolizes a perfectly usable system (as judged by the subject).Object tracking path data within the FOV was also recorded for eachtest and each test subject.Conclusions: An initial system for assisting the blind in reaching andgrasping for objects was successfully designed, implemented andtested. Test subjects were able to successfully grasp the object. Futureimprovements to the system will include enhanced robustness ofvision algorithms, and new implementations of physical feedback.These two improvements will act to make the use of the system moreintuitive for the patient.Commercial Relationships: Nii Tete Mante, None; GerardMedioni, None; Armand R. Tanguay, University of SouthernCalifornia (P); Thang Dinh, None; Furkan E. Sahin, None; PatrickJ. Nasiatka, None; James D. Weiland, Second Sight MedicalProducts, Inc. (F)Support: Research to Prevent Blindness, W.M. Keck Foundation;USAMRMC-W81XWH-10-2-0076Program Number: 2776 Poster Board Number: B0030Presentation Time: 8:30 AM - 10:15 AMMagnification, Field of View and Depth of Field in Low VisionAids and Optical InstrumentsIan L. Bailey. School of Optometry, University of California,Berkeley, Berkeley, CA.Purpose: Clinicians prescribing low vision aids or using visualinstruments to examine eyes often need to understand what finedetails can be seen, how much of the object can be seen, and howvisual access depends of the viewing system. Some new simpleconcepts can allow clinicians to estimate the magnitude ofmagnification effects, fields of view and depths of field.Methods: There are several different methods used to quantifymagnification effects at near and this often leads to erroneouspredictions of optical performance. As an alternative, we useEquivalent Viewing Distance (EVD) which is the distance at whichthe object would subtend the same angle that is being subtended bythe image. The size of just-resolvable detail is simply proportional tothe EVD. For collimating systems, the EVD is equal to the equivalentfocal length. For images at finite distances, the EVD is calculated bydividing the eye-to-image distance by the enlargement ratio (ER) . Tounderstand such systems, the clinician needs to know the imagelocation and ER.The Field of View (FoV) is determined by a “field cone’ whose angleis determined by the field limiting aperture and its distance from theeye. The Image Field Aspect Ratio (IFAR) is a diameter-to-distanceratio defining this angle. The width of the FoV is equal to the productof EVD and IFAR. Slit lamps, and most other microscope systemsare analogous to Kelperian telescopes and then, IFAR = approx. 1.0,and the EVD and the FoV will be about equal.A practical estimate of the Depth of Field is given by the square ofthe EVD.Results: These methods can provide an immediate and accurateestimate of EVD, FoV and DoF in hand held magnifiers, standmagnifiers, telescopes for distance or near. It is easy for clinicianobserving a patient to mentally visualize the field cone and EVDplane, and immediately estimate the FoV. The same approach caneasily be applied to the slit lamp and most other visual inspectioninstruments. Once the geometric concepts are grasped, only minimalcalculation skills are required.Conclusions: The concept of Equivalent Viewing Distance simplifiesthe quantification of magnification effects and prediction ofresolvable detail. The image field cone concept when combined withthe EVD, directly and intuitively predicts the width of the FoV. Oncethe EVD is known, the depth of field can be estimated by squaringthe EVD.Commercial Relationships: Ian L. Bailey, NoneProgram Number: 2777 Poster Board Number: B0031Presentation Time: 8:30 AM - 10:15 AMPreference pattern of low vision aids in glaucoma-redefiningguidelinesAparna Rao, Sirajum Monira, Mahasweta Chowdhury. GlaucomaServices, LV Prasad Eye Institute, Patia, India, Bhubaneswar, India.Purpose: To evaluate preference pattern of low vision devices(LVD) in patients with glaucoma to arrive at specific guidelines forprescribing these devices with regards to specific visual disabilities.Methods: Retrospective review of records of glaucoma patientsattending low vision services. Criteria for low vision was defined asbest corrected distance visual acuity