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Marilyn Zúñiga Advisor: Dr. Roorda Supervisor: Dr. Grieve Site: University of California-Berkeley Imaging Intrinsic Signals in the Retina Using Different Powers of Red Light as a Stimulus
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Outline Background –Anatomy of Eye –References Experiment –Adaptive Optics Scanning Laser Ophthalmoscope (AOSLO) –Methods: Dual Frame Imaging Results –Systematic Trend Observed with Higher Energies –Limitations –Future Experiments
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Background: The Retina Fovea
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Motivation In brain imaging, brain function is assessed by looking for changes in scattered light in response to a stimulus Researchers have recently observed similar reflectance changes in the retina in response to a visible light stimulus We want to look for these intrinsic signals in the retina using AOSLO
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Previous Research Detected IR Changes On Subjects After Stimulus Exposure Author Imaging MethodSubject Flash TypeFlash Duration Flash PowerIR Change TsunodaFundusMacaqueWhite1 ms 41.9 cd- s/m 2 Decrease AbramoffFundusHumanGreen3 sec10 cd/m 2 Decrease GrinvaldFundusCatGreen1 secN/A Increase dim stimulus; decrease bright stimulus BizhevaOCT Rabbit in vitroWhite200 ms 2300 photons/ rod/flashIncrease SrinivasanOCTRat in vivoWhite1.3 s 1400 cd/m 2 Increase Roorda and GrieveAOSLOHumanRed0.5-5 sVarious
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Horizontal Scanner Wavefront Correction Vertical Scanner Eye Laser Confocal Pinhole PMT Wavefront Sensing Light Detection Light Delivery Raster Scanning Deformable Mirror Experimental Methods: The AOSLO red on 1.2 degrees (~ 360 microns)
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Method: Dual Frame Imaging Frame 1: Red LaserFrame 2: Infrared Laser red on IR on red on IR on
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Procedure: Intrinsic Imaging of Retina Frame 1: Red LaserFrame 2: Infrared Laser Dual Imaging Sets of 5 Randomized Trials (30 seconds) Constant infrared light (840 nm) Control (no red flash stimulus) Flashes of Red Light (658 nm; 0.5-5 s)
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Image Analysis 1 1)Compensation for Eye Movements –Signals may be detected from different parts of the retina as the eye moves Solution –Stabilization of movies to better extract the signal
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Image Analysis 2 2)Compensation for Eye Blinking - Intensity changes due to blinking are larger than the desired signal Solution - Compare stimulated vs. unstimulated region of the retina (ratio of upper to lower half of IR image) Frame 1: Red Laser Frame 2: Infrared Laser
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Intensity Ratio of Stimulated to Unstimulated Retinal Areas 051015202530 Preliminary Testing Standard Deviation Mean of 5 Trials Legend Intensity Ratio Time (seconds) 0.92 0.96 1.00 1.04 1.08 Two Second Red Flash Energy: 2.00E-05 Joules Visible Light Stimulus
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Experiment One: Half Second Red Flash with Designated Powers Time (seconds) Energy (Joules) 1.00E-08 2.14E-082.04E-06 9.55E-07 4.47E-07 2.09E-07 9.77E-08 4.57E-08 Control 9.33E-06 4.37E-06 Intensity Ratio 051015202530 0.92 0.96 1.00 1.04 1.08 051015202530 Standard Deviation Mean of 5 Trials Legend
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Energy (Joules) 1.02E-05 3.12E-05 8.40E-05 7.26E-05 5.16E-05 Control Experiment Two: Three Second Red Flash with Designated Powers Time (seconds) Intensity Ratio 0.92 0.96 1.00 1.04 1.08 510152025300510152025300 Standard Deviation Mean of 5 Trials Legend
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Image of Retina Before Stimulation Image of Retina After Stimulation
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Summary/Conclusion Systematic change (increase in scattered lR light in response to stimulation) observed with higher flash energies and a longer flash duration Future Plans More testing with different stimuli and possibly patients with retinal disease
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Acknowledgements Austin Roorda; Advisor Kate Grieve; Supervisor Kaccie Li Ethan Rossi Pavan Tiruveedhula Pinky Weiser Yuhua Zhang Funding Provided by NSF and the Center for Adaptive Optics Grant No. AST- 9876783
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Thank you! Questions?
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