Imaging Intrinsic Signals in the Retina Using Different Powers of Red Light as a Stimulus

1. Imaging Intrinsic Signals in the Retina Using Different Powers of Red Light as a Stimulus Marilyn Zúñiga Advisor: Dr. Roorda Supervisor: Dr. Grieve Site: University of California-Berkeley

2. 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

3. Background: The Retina Fovea

4. 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

5. Previous Research

6. Laser Light Delivery Light Detection PMT Wavefront Sensing red on Confocal Pinhole red on Wavefront Correction Deformable Mirror Horizontal Scanner Raster Scanning Vertical Scanner Eye Experimental Methods: The AOSLO 1.2 degrees (~ 360 microns)

7. red on IR on red on IR on Method: Dual Frame Imaging Frame 1: Red Laser Frame 2: Infrared Laser

8. Dual Imaging Constant infrared light (840 nm) Sets of 5 Randomized Trials (30 seconds) Flashes of Red Light (658 nm; 0.5-5 s) Control (no red flash stimulus) Procedure: Intrinsic Imaging of Retina Frame 1: Red Laser Frame 2: Infrared Laser

9. Image Analysis 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

10. Image Analysis 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 2: Infrared Laser Frame 1: Red Laser

11. Legend Standard Deviation 1.08 Mean of 5 Trials 1.04 1.00 0.96 0.92 0 5 10 15 20 25 30 Preliminary Testing Two Second Red Flash Intensity Ratio of Stimulated to Unstimulated Retinal Areas Visible Light Stimulus Intensity Ratio Time (seconds)

12. 0 0 5 5 10 10 15 15 20 20 25 25 30 30 1.08 Legend 1.04 Standard Deviation 1.00 Mean of 5 Trials 0.96 0.92 Experiment One: Half Second Red Flash with Designated Powers Intensity Ratio Time (seconds)

13. 1.08 1.04 1.00 0.96 0.92 0 0 5 5 10 10 15 15 20 20 25 25 30 30 Experiment Two: Three Second Red Flash with Designated Powers Legend Standard Deviation Mean of 5 Trials Intensity Ratio Time (seconds)

14. Image of Retina Before Stimulation Image of Retina After Stimulation

15. 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

16. 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

17. Thank you! Questions?