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