Adaptive Optics for Vision Science: Principles, Practices...

Adaptive Optics for Vision Science:Principles, Practices, Design

and Applications

Generated from Discussions at theCfAO Spring Retreat

March 23, 2003

Jason Porter, Abdul Awwal, Julianna LinHope Queener, Karen Thorn

(Editorial Committee)

Chapters of AO ManualI. Introduction (David Williams)

II . Wavefront Sensing2. Aberration Structure of the Human Eye (Pablo Artal)3. Wavefront Sensing and Diagnostic Uses (Geunyoung Yoon)

III. Wavefront Correction with Adaptive Optics4. Mirror Selection (Nathan Doble and Don Miller)5. Control Algorithms (Li Chen)6. Software/User Interface/Operational Requirem ents (Ben Singer)7. AO Assembly, Integration and Troubleshooting (Brian Bauman)8. System Performance: Testing, Procedures, Calibration and Diagnostics

IV. ApplicationsA. Retinal Imaging

9. Fundam ental Properties of the Retina (Ann Elsner)10. Strategies for High Resolution Retinal Im aging (Austin Roorda, Remy Tumbar)11. Design Examples (Krishna Venkateswaran, Don Miller, Heidi Hofer)

B. Vision Correction12. Customized Vision Correction Devices (Ian Cox)13. Customized Refractive Surgery (Scott MacRae)14. Visual Psychophysics (UC Davis Team, headed by Jack Werner)15. Wavefront to Phoropter Refraction (Larry Thibos)16. Design Examples (Scot Olivier, Heidi Hofer)

V. Appendix/Glossary of Terms (Hope Queener, Joseph Carroll)

Chapter 1: Introduction

• History of adaptive optics

• How well does AO work for astronomy?

• Why do we need AO for the eye?

• Examples of benefits reaped from current AO visionscience systems

Chapter 2: Aberration Structure ofthe Human Eye

• Static and dynamic properties of the eye’s aberrations

• Chromatic aberration

• Polarization properties

• Stiles-Crawford Effect?

• “Fried parameter” for the eye?

• Anisoplanatism in the eye?

Chapter 3: Wavefront Sensing andDiagnostic Uses

• Beacon– Size and Power– Illumination schemes (Off-axis, 1/4 wave plate)– Wavelengths for wavefront sensing (Retinal characteristics)– SLD vs. laser diode vs. laser (Speckle considerations)– Issues with simultaneous observation of beacon/visual

stimulus• MPE’s• Subject Interface/Operational requirements

– Bite bar/Head & Chin Rest– Pupil/Retinal Tracking (Tip/tilt)

• Types of wavefront sensors– Curvature– Pyramid

– Shack-Hartmann

Chapter 3: Wavefront Sensing andDiagnostic Uses

• Lenslet array– Focal Lengths– Lenslet Spacing– Dynamic Range vs. Sensitivity

• CCD Camera properties– Sensitivity, fill factor, pixel size, quantum efficiency,

progressive vs. interlaced, .. .

• Centroid algorithm

• Wavefront reconstruction

• Potential diagnostic uses of wavefront sensors

• Summary Table: Lenslet spacing, focal length,measurement range/sensitivity

Chapter 4: Mirror Selection

• Continuous faceplate (Xinetics, BMC, Intellite)

• Segmented mirrors– Piston (BMC)

– PTT (IrisAO)– Piston w/Phase wrapping (Liquid Crystal, 20/10)

– PTT w/Phase wrapping

• Membrane mirror (Lucent, OKO)• Bimorph mirrors

• Summary Table: Mirror tested, stroke, waves ofcorrection, order of correction (number actuators)

Chapter 5: Control Algorithms

• Lenslet and actuator arrangement

• Lenslet and CCD camera pixel arrangement

• Zernike mode reconstruction used to control mirror

• Direct Slope algorithm

• Influence functions / measurement

• Algorithms to optimize AO systems– PID

– Feedback

• Summary

– Smith

Chapter 6: Software/OperationalRequirements

• Functions and variables user can adjust duringoperation (camera exposure, etc.)

• Pop-up displays/windows– Actuator map

– Spot pattern– Traces to display (RMS, Strehl, Zernike modes, …)

• Handling of bad actuators

• Summary

Chapter 7: AO Assembly andIntegration

• Beacon placement and integration

• Alignment procedures, issues, techniques

• Types of optical components used

• Integration/testing of software

• Troubleshooting ideas

Chapter 8: System Performance

• Spatial and Temporal characteristics of correction

• Power Spectra calculations

• Disturbance rejection curves

• Strehl ratio/PSF measurements/calculations

• Performance vs. different parameters (beaconbrightness, field angle, …)?

• Summary Table and Figures of above criteria– Results from Xinetics, BMC, IrisAO

Chapter 9: Fundamental Propertiesof the Retina

• Basic layout of the eye

• 3-Dimensional structure of the retina

• Reflection/Absorptance properties

• Properties of the photoreceptor mosaic– Rods and cones– Waveguiding nature

– Trichromatic nature of the cone mosaic

• Cell layers of particular interest for imaging

Chapter 10: Strategies for HighResolution Retinal Imaging

• Flood illumination systems– Lamp parameters (flash duration, intensity, wavelength)– Bleaching lights and systems

– Field size/eccentricity– Scientific cameras

• Scanning (Confocal) systems– Scanning mirrors

– Wavelengths– Field size/eccentricity

– Camera selection

Chapter 10: Strategies for HighResolution Retinal Imaging

• OCT systems– Flood illuminated vs. Scanning

• Future ideas?– DIC (Differential Interference Contrast)– Phase Contrast

– Polarization Techniques– Two-photon

– Fluorescence/Auto-fluorescence

• Survey of post-processing/image enhancementstrategies

Chapter 11: Design Examples forRetinal Imaging

• Detailed Layouts, Numbers, Noise Analysis,Limitations for:

• Houston AOSLO• Indiana University AO Coherence Gated System• Rochester 2nd Generation AO System

Chapter 12: Customized VisionCorrection Devices

• Using wavefront sensing to improve and enhance thedesign of customized contact lenses and IOLs

Chapter 13: Customized RefractiveSurgery

• Wavefront guided laser refractive surgery (LASIK,LASEK)

Chapter 14: Visual Psychophysics

• Display types and calibration:– CRT (CSF) - magnification/resolution issues– Liquid Crystal

– DLP (Visual acuity)– Plasma?

• Types of software - separate from AO software– Creating a visual stimulus– How to determine acuity - Staircase and Quest Procedures

Chapter 15: Wavefront toPhoropter Refraction

• Establishing a metric, based on wavefront sensordata, that best correlates with subjective visualperformance

• Using wave aberration data to most accuratelypredict a patient’s subjective refraction

Chapter 16: Design Examples

• Detailed Layouts, Numbers, Noise Analysis,Limitations for:– Visual Psychophysics:

• LLNL/UR/B&L AO Phoroptor• UC Davis AO Phoropter

• Rochester 2nd Generation AO System

Appendix & Glossary

• Laser safety calculations

• Other ideas?• Glossary to define frequently used terms