Optical Coherence Tomography: Pearls for the Anterior Segment Surgeon Basic Science Michael Stewart, M.D.

Transcription

1 Optical Coherence Tomography: Pearls for the Anterior Segment Surgeon Basic Science Michael Stewart, M.D. Disclosure OCT Optical Coherence Tomography No relevant financial relationships I will refer to off-label use of medications Laser Cross section What happens when light hits the retina? What happens when light hits the retina? What happens when light hits the retina? Only 10-5 to 10-9 of incident light is reflected back. Transmission Absorption Reflection OCT images are created by What pigments are found within the eye? Ocular Pigments: melanin, xanthophylls, hemoglobin 1. Ocular pigments 2. Interfaces with differing refractive indices 1. Xanthophylls 2. Hemoglobin 3. Melanin 1

2 OCT Imaging = Optical Biopsy Normal Macular Anatomy Xanthophyll Highest concentration in macula What color is the retina? Melanin OCT B-Scan Normal Macular Anatomy R + T = 1 Fresnel Equations Pre-operative macular hole NFL GCL IPL OPL ONL ELM IS/OS RPE Choroid For light polarized in Ө the plane of the diagram: i R s = (sin(ө i - Ө t)/sin (Ө i + Ө t)) 2 For light polarized perpendicular to the plane of the diagram: R p = (tan (Ө i - Ө t)/tan(ө i + Ө t)) 2 Ө r Ө t Post-operative For non-polarized light: R = (R s + R p)/2 Modified from: Retina 5 th Ed, Chapter 3, Optical Coherence Tomography Within retinal tissue this is: 10-5 to 10-9 Previous vitrectomy with silicone oil 20 minutes later Aqueous 2

3 OCT tomogram of cervical epithelium Optical coherence tomography showing prostatic capsule and cancer cells underneath the thin layer Resolution 150 µ TD-OCT: Resolution 10 µ SD-OCT Resolution 3 to 6 µ 3.5 or 6 mm 3

4 Spectral Domain OCT (SDOCT) Imaging Faster image acquisition A-scans/sec: currently available instruments. 200, ,000 A-scans/sec: research instruments. Higher density scans over larger areas, image averaging to improve image quality, fewer eye motion artifacts. SDOCT Imaging of Macula Qualitative assessment of retinal anatomy: Subretinal Fluid PED Subretinal Fluid SDOCT Imaging of Wet AMD Segmentation of retinal layers necessary for quantitative assessments: ILM segmentation SDOCT Imaging of Wet AMD Segmentation algorithms result in reliable retinal thickness maps: Retinal thickness VA: 20/100 SDOCT Imaging of Wet AMD: Anti-VEGF Therapy Retinal thickness map Retinal thickness RPE segmentation ILM segmentation RPE segmentation RPE segmentation VA: 20/40 Anti-VEGF Therapy: 1 month post-injection SDOCT Imaging of Dry AMD Segmentation algorithms result in reliable RPE elevation (drusen) maps (Cirrus, software 6.0): SDOCT Imaging of Wet AMD Segmentation algorithms result in reliable RPE elevation (PED) maps (Cirrus, software 6.0): SDOCT Imaging of Wet AMD Vitreomacular interface abnormalities RPE RPE floor RPE RPE floor Vol: 0.58mm 3 Epiretinal membrane RPE segmentation RPE Elevation map Gregori G, Wang F, Rosenfeld PJ, et al. Spectral domain optical coherence tomography imaging of drusen in nonexudative age-related macular degeneration. Ophthalmology. 2011;118(7): RPE segmentation Retinal thickness RPE Elevation map 4

5 Macular edema RPED 5

6 Optical Coherence Tomography: Pearls for the Anterior Segment Surgeon Retina Michael Stewart, M.D. 6

7 Why this shadow? Why this shadow? Gas bubble 7

8 1945µ 2819µ 8

9 2 weeks later OS 20/40 Stage 2 OD 20/25 Stage 1 Lamellar hole Cyst? Lamellar hole 9

10 Epiretinal Membrane 20/40 Pre-Op 20/30 Post-Op 10

11 9/29/ /31/ /30/

12 1/11/2006 Subretinal fluid RPED Case 71 yo man with wet AMD OS Multiple injections for the last 12 months Complains of worsening in VA after treatment Case 74 y.o. man decreased vision OD (20/200) Wet AMD Dry AMD 20/200 Ranibizumab #1 Case After 1 month Case Monthly Injections 73 y.o. woman with neovascular AMD VA: 20/40 Ranibizumab #1 Vol: 0.73 mm 3 VA: 20/20 Ranibizumab #2 Case 3 65 y/o woman with a vascularized, hemorrhagic PED Vol: 0.63 mm 3 20/80 Ranibizumab #2 VA: 20/20 Ranibizumab #3 Vol: 0.56 mm 3 Color photo Early FA Late FA 12

13 Baseline Anti-VEGF #1, Anti-VEGF #2 4w post Inj. #2 Observed 6w post Inj. #2 Observed Volume: 6.9 mm 3 Volume: 2.6 mm 3 Case 4: Dosing Every 2 Weeks 66 year old woman 10 injections: Bev X6, Ran X4 (~q5wks) July 2007 FA-early 20/50 FA-late OCT Baseline 20/200 Ran Inj. #1 2 w post Inj. #1 20/40 Bev Inj. #2 8w post Inj. #2 Anti-VEGF #3 Volume: 3.2 mm 3 1 year later 20/200 2 w post Inj. #2 20/30 Ran Inj. #3 4w post Inj. #3 Observed Volume: 3.9 mm 3 2 w post Inj.#3 20/30 Bev Inj. #4 Volume: 1.6 mm 3 Modified from: Stewart MW, et al. Pharmacokinetic Rationale For Dosing Every 2 Weeks Versus 4 Weeks With Intravitre Ranibizumab, Bevacizumab, And Aflibercept (Vascular Endothelial Growth Factor Trap-eye). Retina Dec

14 Diagnosis? IOP = 4 OD BDR OS Pre-op Baseline 1 day Post-op Following steroid injection OD 1 month later OS 6 months VA: 20/20 c/o superior field defect 14

15 Acute retinal artery occlusion Inner retina thickening Retinal thinning Treatment options: 1. External beam irradiation 2. Systemic chemotherapy Treatment 1.Observation 2.Laser photocoagulation 15

16 NFL Lines in nasal periphery 65 y.o. s/p scleral buckle for RD Now with VA of 20/100 for 6 months. 2 nd opinion: 68 y.o with iritis and VA of 20/40 OU 16