OCT mini-symposium. Presenters. Donald Miller, Indiana Univ. Joseph Izatt, Duke Univ. Thomas Milner, Univ. of Texas at Austin Jay Wei, Zeiss Meditec

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1 OCT mini-symposium Presenters Donald Miller, Indiana Univ. Joseph Izatt, Duke Univ. Thomas Milner, Univ. of Texas at Austin Jay Wei, Zeiss Meditec

2 Starlight, eyebright Canberra Times, Australia

3 Combining the strengths of adaptive optics and coherence gating Adaptive Optics (high transverse resolution) Coherence Gating (high axial resolution, i.e. optical sectioning) AO C-G Retina Camera (high transverse & axial resolution)

4 OCT Tomography (x-z image, Wei) Color Doppler OCT (flow detection, Izatt) En face scanning (x-y image, Izatt) Polarizationsensitive OCT (Milner) Flood-illumination (photodiode array, Milner CCD, Miller) Clinical OCT (Wei)

5 High-Resolution Retinal Imaging Using AO and OCT Junle Qu, Ravi Jonnal, and Karen Thorn Donald Miller

6 Adaptive optics is being integrated into three main architectures of retina cameras. 1. Flood-illumination Chinese Acad. Of Sciences (China), Indiana, Lawrence Livermore, Moscow State Univ. (Russia), Murcia (Spain), Observatoire de Paris (France), Rochester, UC San Diego 2. Scanning laser ophthalmoscope Houston, Imperial Col. (UK), Lawrence Livermore, Murcia (Spain), National Univ (Ireland), Rochester, Schepens, UC-Berkeley, UC-San Diego, Waterloo (Canada) 3. Coherence gating (OCT) Indiana, Lawrence Livermore, National Univ (Ireland), Observatoire de Paris (France), Rochester, UC-Davis, Univ. College (UK), Univ of Kent (UK)

7 Adaptive optics coherence-gated retina camera New medical imaging modality (1991*) Optical analogy of ultrasound Axial resolution ~ 1 / coherence length of the light source Detected signal = Ψ ref + Ψ retina 2 low coherent light source Aberrated wavefront Eye reference mirror = Ψ ref 2 + Ψ retina Ψ ref Ψ retina cos(φ ref - φ retina ) layer 1 Wavefront sensor CCD detector camera *Huang, Swanson, Lin, Schuman, Stinson, Chang, Hee, Flotte, Gregory, Puliafito, Fujimoto, Science 254, 1178 (1991).

8 Volume of the 3-D point spread function for various combination of AO and camera architectures. optical axis lateral resolution axial resolution Lateral Depth Voxel volume Commercial cslo 8.7 µm 300 µm 71,000 µm 3 Commercial OCT 25 µm 10 µm 15 X smaller AO-Flood illumination 2.2 µm very poor AO-cSLO 2.2 µm 60 µm 80 X smaller AO-OCT 2.2 µm 3 µm 1,593 X smaller

9 choriod photoreceptors outer nuclear layer outer synaptic layer inner nuclear layer inner synaptic layer ganglion cell layer 100 µm comm. OCT AO cslo AO OCT optic fiber layer comm. cslo AO flood illumination

10 choriod photoreceptors outer nuclear layer Current PSFs outer synaptic layer inner nuclear layer inner synaptic layer ganglion cell layer 100 µm comm. OCT AO cslo AO OCT optic fiber layer comm. cslo AO flood illumination

11 En-face coherence-gating with a CCD Replacing single point photodetector with a 2-D video sensor enables parallel detection without scanning. Detected signal = Ψ ref + Ψ retina 2 = Ψ ref 2 + Ψ retina Ψ ref Ψ retina cos(φ ref - φ retina ) layer 1 low coherent light source Wavefront sensor four λ/8 steps Aberrated wavefront PZT CCD camera Eye reference mirror

12 Optical layout of the coherence gated adaptive optics ophthalmoscope Sub-systems: 1. 1D OCT 2. AO system 3. En-face coherence gating SLD (S-H) SLD (2-D) SLD (1-D scan) Xinetics (PMN-37) dichroic mirror dichroic mirror Eye photodiode (1-D scan) dichroic mirror pzt mirror voice coil reference arm retinal CCD camera CCD dichroic mirror Hartmann- Shack wavefront sensor

13 Photograph of the coherence gating AO retina camera 1-D OCT retina CCD S-H WS Xinetics mirror 3 SLDs reference channel Lucky patient goes here

14 Close up view of the bite bar stage retroreflector on voice coil stage mirror on PZT 3 SLDs Test patient

15 Axial Cross sections through the reconstructions reveals depth information of the bovine fundus Flood-illumination of an in vitro bovine retina (no coherence gating) Cross sectional slices (coherence gating) 902 µm 365 µm 270 µm 65 µm db

16 In vitro goldfish fundus 355 to 394 µm 154 to 172 µm 65 µm 270 µm Tomographic (X-Z) En face (X-Y)

17 AO-OCT Retinal Images for One Subject NFL X-Z slice through 41 En face reconstructions Single en face (X-Y) reconstructions 421 µm RPE & choroid Setup: - 10 micron step size - 42 reconstructions - 6 deg eccentricity - focus on photoreceptors - AO correction - track retinal position 15 µm

18 Conclusion AO-OCT retina camera has been developed. En face OCT images of in vitro bovine and goldfish retinas reveal clear stratification of the fundus. AO & en face OCT images of the living human retina suggest there is sufficient sensitivity to study the nerve fiber layer, photoreceptors, RPE, and choroid.