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To See or To See or Not To See:Not To See:
Visual Acuity With and Visual Acuity With and Without Adaptive OpticsWithout Adaptive Optics
By: Luis A HenryBy: Luis A HenryUniversity of HoustonUniversity of Houston
ExperimentExperiment
How Does Visual Acuity change with How Does Visual Acuity change with aberrations and pupil size?aberrations and pupil size?
Visual Acuity Visual Acuity
DefinitionDefinition: The : The ability to resolve fine ability to resolve fine detail ( usually detail ( usually determined by a determined by a Snellen chart ).Snellen chart ).
Limited by aberrations & pupil Limited by aberrations & pupil sizesize
http://www.swordtail.free-online.co.uk/eyechart.gif
AOSLOAOSLO
Stands For: Adaptive Optics Scanning Stands For: Adaptive Optics Scanning Laser OphthalmoscopeLaser Ophthalmoscope
Major components:Major components:Adaptive Optics systemAdaptive Optics systemScanning Laser OphthalmoscopeScanning Laser Ophthalmoscope
Adaptive Optics
AO ON
AO OFFAdaptive Optics: Adaptive Optics: corrects corrects aberrations that aberrations that cause blur in the cause blur in the retinal imageretinal image
Scanning Laser OphthalmoscopeScanning Laser Ophthalmoscope
SLO: an efficient method of imaging and SLO: an efficient method of imaging and presenting stimulipresenting stimuli
Use a modulated laser to construct an image over Use a modulated laser to construct an image over timetime
How an SLO WorksHow an SLO Works
University of Houston University of Houston Adaptive Optics SLOAdaptive Optics SLO
light light deliverydelivery
wavefrontwavefrontsensingsensing
eyeeyerasterrasterscanningscanning
wavefrontwavefrontcompensationcompensation
lightlightdetectiondetection
Visual Acuity MeasurementsVisual Acuity Measurements
SLO forms an Raster image of an E SLO forms an Raster image of an E directly on retina directly on retina Four Alternative ForcedFour Alternative Forced--Choice Tumbling Choice Tumbling E or “illiterate E test”E or “illiterate E test”
Find the smallest size E that can be Find the smallest size E that can be properly identifiedproperly identified
Raster ScanRaster Scan
The scanning mirrors use the laser beam The scanning mirrors use the laser beam to form raster which is 512 pixels by 480 to form raster which is 512 pixels by 480 lines lines 20/20 image
1
2
3
4
5
1 minute of arc
ConditionsConditions
1) 6mm pupil uncorrected 1) 6mm pupil uncorrected –– expect large expect large PSF & wave aberrationPSF & wave aberration
2) 6mm pupil corrected with AO 2) 6mm pupil corrected with AO –– expect a expect a compact PSF & near perfectly flat wavecompact PSF & near perfectly flat wave
3) 3mm pupil corrected with AO 3) 3mm pupil corrected with AO –– expect expect larger PSF (less compact than condition larger PSF (less compact than condition two) & near perfectly flat wavetwo) & near perfectly flat wave
Conditions Conditions
Condition 2Condition 26mm pupil6mm pupilAO correctedAO corrected
Condition 1 Condition 1 6mm pupil6mm pupilUncorrectedUncorrected
Condition 3Condition 33 mm pupil 3 mm pupil AO CorrectedAO Corrected
An E is presented and the subject is asked to makeAn E is presented and the subject is asked to makea choice of the orientationa choice of the orientation
Visual Acuity Plot Visual Acuity Plot
Visual Acuity LAH
0
10
20
30
40
50
60
70
80
90
100
20/5 20/7.5 20/10 20/12.5 20/15 20/17.5 20/20
Image Size
% C
orre
ct 3mm Pupil w/ AO6mm Pupil w/o AO6mm Pupil w/ AO
Psychometric Function FitPsychometric Function Fit
VA= Threshold *20 VA= Threshold *20 VA= .641* 20 = 12.82VA= .641* 20 = 12.82VA=20/12.82VA=20/12.82
ResultsResults
VA Comparison
0.0000 0.5000 1.0000 1.5000 2.0000 2.5000 3.0000
6mm AO
3mm AO
6mm no AO
Con
ditio
ns
Visual Acuity
SASVARLAHJEFSP
20/20 20/17.5 20/15 20/12.5 20/10 20/7.5 20/5
Results Results VA Comparison
0.0000
0.5000
1.0000
1.5000
2.0000
2.5000
3.0000
SP JEF LAH AR ASV S
Subject
Visu
al A
cuity 6mm AO
3mm AO6mm no AO
20/5
20/7.5
20/10
20/12.5
20/15
20/17.5
20/20
Final analysisFinal analysis
AO can help improve visual acuity, but is AO can help improve visual acuity, but is limited by:limited by:
Sampling limits (photoreceptor density)Sampling limits (photoreceptor density)Neural limitations Neural limitations
References & AcknowledgementsReferences & Acknowledgements
http://www.mdsupport.org/library/acuity.htmlhttp://www.mdsupport.org/library/acuity.htmlhttp://webvision.med.utah.edu/KallSpatial.htmlhttp://webvision.med.utah.edu/KallSpatial.htmlhttp://www.bcs.rochester.edu/people/williams/yoon.2002.phttp://www.bcs.rochester.edu/people/williams/yoon.2002.pdfdfAustin RoordaAustin RoordaSiddharth Poonja Siddharth Poonja This project was supported by a Research Experiences This project was supported by a Research Experiences for Undergraduates (REU) supplement to the national for Undergraduates (REU) supplement to the national Science Foundation and Technology Center for Adaptive Science Foundation and Technology Center for Adaptive optics, managed by the University of California at Santa optics, managed by the University of California at Santa Cruz under a cooperative agreement No. ASTCruz under a cooperative agreement No. AST--98767839876783
Austin Roorda LabAustin Roorda Lab
Thank YouThank You
Condition 1Condition 1
Subject LAH, 6 mm Subject LAH, 6 mm pupil without AO pupil without AO
An E is presented An E is presented and the subject is and the subject is asked to make a asked to make a choice or orientationchoice or orientation
Condition 3Condition 3
Subject LAH, 3 mm Subject LAH, 3 mm pupil with AO pupil with AO
An E is presented and An E is presented and the subject is asked the subject is asked to make a choice or to make a choice or orientationorientation
Condition 2Condition 2
Subject LAH, 6 mm Subject LAH, 6 mm pupil with AO pupil with AO
An E is presented An E is presented and the subject is and the subject is asked to make a asked to make a choice of the choice of the orientationorientation