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Optical Coherence Tomography (OCT)
- 1. OCT IN RETINAL DISEASES DR.SHAH-NOOR HASSAN FCPS,FRCS Assistant Professor BSMMU
- 2. History FIRST OCT IMAGES – 1991 (SHUANG) OCT technology was conceived in the Department of Electrical Engineering and Computer Science at Massachusetts Institute of Technology James Fujimoto, Carmen Puliafito, and Eric Swanson In 1992 the first commercial optical coherence tomography (OCT) company was started. It was called Advanced Ophthalmic Devices (AOD)
- 3. Advantages • Noncontact and noninvasive technique • The cross sectional nature of the image provides depth information • To detect and objectively measure - Morphological changes - Retinal thickness - NFL thickness - Retinal volume - Other parameters of optic disc • Stored in memory, making comparison over time simple and accurate.
- 4. Limitations • Being new technology the instruments are relatively expensive • Scan quality is dependent on the skill of OCT operator • May not be possible with unco-operative patients • Exploration is limited to the posterior pole. • Images are degraded in the presence of media opacity.
- 6. • Normal Macula • Role of OCT • Interpretation of OCT • Vitreo-retinal interface disorders • Retinal disorders • Subretinal disorders
- 8. Colour codes Reflectivity Optically empty Hypo Intermediate Hyper black Blue-green yellow red Vitreous Nuclear layers Plexiform layers NFL and RPE
- 11. ROLE OF OCT • Ancillary aid in diagnosis • Evaluate course of disease • Monitor treatment efficacy
- 13. Two ways of analyzing OCT scan 1.Qualitative 1. Morphology 2. Reflectivity 2.Quantitative 1. Thickness 2. Volume 3. Area 19
- 14. morphological changes: •Overall retinal structural changes •Changes in retinal outline •Intraretinal structural changes •Changes in posterior layers Anomalous structures: 1.pre-retinal/epiretinal 2.intraretinal 3.subretinal Qualitative analysis 20
- 15. Quantitative analysis is possible because the OCT 3 software is able to identify and "trace" two key layers of the retina, the NFL and RPE. Thickness Volumetry Surface mappings Caliper can be used to measure any other dimension or distance Quantitive analysis 21
- 16. OCT IMAGING OF MACULA FOVEOLA RPE NERVE FIBER LAYER MACULAR THICKNESS MAP
- 17. INTERPRETATION OF ABNORMAL OCT FINDINGS •HEMORRHAGES • SCARS OR FIBROSIS • HARD EXUDATES • INFLAMMATORY INFILTRATE INTO ANY LAYER OF RETINA HYPERREFLECTIVITY
- 18. INTERPRETATION OF ABNORMAL OCT FINDINGS •Retinal Edema •Serous Fluid •Hypopigmentation of RPE HYPOREFLECTIVITY
- 19. SEROUS FLUID - OPTICALLY TRANSPARENT BLOOD – ENHANCED REFLECTIVITY EXUDATE – MODERATE REFLECTIVITY INTERPRETATION OF ABNORMAL OCT FINDINGS NATURE OF FLUID
- 20. Interpretation of OCT ?Interpretation of OCT ? 1.How is the vitreo – retinal interface? 2.What does the foveal contour look like? 3.Features of neurosensory retina ? 4. Is the red line of RPE-CCC intact or disrupted?
- 21. VITREO – RETINAL INTERFACE
- 23. MACULAR HOLES
- 25. RPE - CCC
- 26. Vitreo - retinal interface disorders
- 27. ERMERM •TYPE OF ATTACHMENT TO THE RETINAL SURFACE •POST OPERATIVE RESOLUTION
- 29. VMT
- 30. MACULAR HOLEMACULAR HOLE •STAGE THE MACULAR HOLE •POST TREATMENT FOLLOW UP •DIFFERENTIATE-FULL THICKNESS MACULAR HOLE FROM LAMMELAR HOLE AND PSEUDO HOLE
- 33. LAMELLAR HOLE
- 35. PSEUDOHOLE…
- 36. PSEUDOHOLE…
- 38. DIABETIC MACULOPATYDIABETIC MACULOPATY • SUBTLE THICKNESS • VMT • SEROUS DETACHMENT • CME • LOCATION OF HARD EXUDATES
- 39. Pattern 1. Sponge-like retinal thickening Hard exudates Sponge-like
- 40. Pattern 2.Cystoid spaces (partial thickness) Cystic spaces
- 41. Pattern 3.Cystoid spaces (full thickness) Pattern 2.Cystoid spaces (partial thickness)
- 42. Pattern 4. Subfoveal serous RD
- 43. Pattern 5. Taut Posterior Hyloid memb (Focal) Focal foveal traction Vitreoschisisis
- 45. p302519
- 47. CNVMCNVM
- 48. CLASSIC CNVM
- 49. OCCULT CNVM
- 51. PED
- 52. PIGMENT EPITHELIAL DETACHMENT Elevation of the neurosensory retina optically clear space (black on OCT) underneath them The angle of the edge of detachment is typically acute
- 53. HAEMORRHAGIC PED
- 54. SEROUS PED
- 55. CSCRCSCR •OBSERVE THE RESOLUTION •DIFFERENTIATE FROM CNVM •IDENTIFY CYSTOID MACULAR DEGENERATION
- 57. OCT in other ocular diseases
- 58. FOVEAL HAEMORRHAGE -- SUBILM HAEMORRHAGE
- 59. Retinoschisis
- 61. IPCV
- 62. OPTIC NERVE HEAD PIT
- 63. VKH
- 65. Conclusion • OCT is a revolutionary diagnostic tool in the Era of modern retinal treatment. • Being noninvasive it is safe and accessible to the patients. • Both in the anterior and posterior segment it has proven to be an accurate tool for diagnosis and treatment. • Per operative use of OCT has taken it to a new height.
- 66. Thank you
Hinweis der Redaktion
- OCT technology was conceived in the Department of Electrical Engineering and Computer Science at Massachusetts Institute of Technology. James G. Fujimoto, PhD, professor of electrical engineering and computer science, and his students had collaborated with Carmen A. Puliafito, MD, MBA, OSN Retina/Vitreous Section Editor, who was then at the Massachusetts Eye and Ear Infirmary. “The [initial] collaboration was investigating the applications of femtosecond lasers for surgery,” Dr. Fujimoto told OSN. “At that time, we were also interested in using femtosecond light pulses to measure distances in the eye.” In the late 1980s, this technology was being investigated for the measurement of anterior structures. Joel S. Schuman, MD, an OSN Glaucoma Section Member, was a glaucoma fellow at Massachusetts Eye and Ear at the time and was working on another project in Dr. Puliafito’s laser laboratory in 1989. “I became aware of the technology and realized that it could have an application for measuring retinal thickness,” Dr. Schuman said. In 1991, David Huang, MD, PhD, who was a student under Dr. Fujimoto in the Harvard/MIT Health Sciences and Technology program, was working on this project, and he had the idea of generalizing axial scans to transverse images. “I thought this is much more useful as an imaging modality than just a ranging or thickness measurement,” Dr. Huang said. “So we got a bunch of data and plotted it out [on a false color scale] to get the image, and it looked amazing.” The team demonstrated the first OCT images, which were done in the retina ex vivo, and the data were reported in Science in 1991. Dr. Huang was the first author of the paper, which is widely regarded as the first demonstration of OCT
- Instead of a knife, light is used. Instead of viewing a stained section under a microscope, we are presented with a "false-color" view with micron level resolution.
- This sources that can emit light over a broad range of frequencies Light from a broadband, near infrared source 820 nm and a visible aiming beam is combined and coupled into one branch of fiber-optic Michelson interferometer. has a short coherence length………………………,either constructively and destructively
- that is reflected and backscattered from different microstructures in the retina and light reflected from reference mirror at known distances
- As against B-scan and fluorescein, depth information similar to using a thin slit on a cornea with a slitlamp microscope. Resulting images can be- -Compared with images obtained during follow-up examinations
- The coherent light is only minimally visible to the patient, so is very comfortable and
- to purchase e.g in dense cataract Thus OCT is difficult/impossible to perform in cases of:
- Qualitative analysis of the OCT scan includes observation of the reflective qualities of the retinal structures. The OCT software assigns "cooler" colors (green, blue) to structures with lower reflectivity. It assigns "warmer" colors (yellow, orange, red) to more highly reflective structures. White represents the most highly reflective structures, and black represents the least reflective structures The most highly reflective anatomical layers are the NFL and the RPE.
- The software can then measure the distance between these two layers, which represents retinal thickness. Multiple thickness measurements can be interpolated into a volume measurement of the
- THE NORMAL FOVEA IS IDENTIFIED BY ITS CHARACTERISTIC DEPRESSION OF THE INNER RETINAL BORDER SECONDARY TO THE LATERAL DISPLACEMENT OF TISSUE ANTERIOR TO NERVE FIBER LAYER . THE UPPERMOST FIGURE IS COLOR CODED , CROSS SECTIONAL MAP ALONG THE VERTICAL LINE . THE CENTRAL THINNING CORRESPONDS TO FOVEOLA AND WHITE LINES MARK THE VITREORETINAL AND RPE BOUNDARIES OF RETINA . THE LOWER LEFT MAP IS THE COLOR CODED MACULAR THICKNESS MAP WHEREIN BLUE COLOR REPRESENTS THINNER RETINA AND YELLOW GREEN ,THICKER RETINA. THE CENTER MAP GIVES THE QUANTATIVE MEASUREMENTS OF NINE SECTORS.
- REFLECTIVITY PATTERN OF THE SCANNED IMAGES IS USED TO INTERPRET ABNORMAL FINDING AS FOLLOWS ; HYPERREFLECTIVITY CAN BE CAUSED BY HEMORRHAGES , SCARS OR FIBROSIS , HARD EXUDATES AND INFLAMMATORY INFILTRATE INTO ANY LAYERS OF RETINA.
- HYPOREFLECTIVITY MEANS REDUCED BACK SCATTERING MAY BE CAUSED BY RETINAL EDEMA , SEROUS FLUID HYPOPIGMENTATION OF RPE .
- DISTINCTION BETWEEN BLOOD SEROUS FLUID AND EXUDATE IS MADE ON THE BASIS OF REFLECTIVITY SEROUS FLUID IS OPTICALLY TRANSPARENT , BLOOD HAS BOTH ENHANCED REFLECTIVITY AND INCREASED ATTENUATION OF ENHANCED LIGHT .EXUDATE TYPICALLY HAS INTERMEDIATE APPEARANCE BETWEEN BLOOD AND SEROUS FLUID ON OCT IMAGES.
- ERM 1. CLEAR SPACE BETWEEN ERM AND INNER RETINAL LAYERS 2 NO SPACE GLOBALLY ADHERENTERM SEE WHAETER IS UNDERLYING TRACTION…1. CELLOPHANE MACULOPATHY, 2. CRINKLED CELLOPAHNE MACULOPATHY, 3. MACULAR PUCKER IT HELPS SURGEON IN IDENTIFTING THE RIGHT PLANE OF CLEV AGE….
- CONFINED TO OUTER RETINAL LAYERES GIVES A SHADOWING EFFECT AND HARD EXUDATES ARE SEEN AS HYPERREFLECTIVE SHADOWS…
- OCT SHOWS MACULAR THICKENING WITH FULL THICKNES CYSTIOD SPACES UNDER THE FOVEA WITH INTERVENING SEPTAE..WITH ADJOINING SMALL SEPTAE…
- OCT SHOWS LARGE CYSTOID SPACES WITH INTERVENING SEPTAE…
- OCT SHOWS MACULAR THICKENING..IN THE FOVEA WITH HYPOREFLECTIVE SPACESIN ADDITION THERE IS HYPOREFLECTIVE AREA IN THE SUFOVEAL REGION CONSISTENT WITH SUBFOVEAL SEROUS RETINAL DETACHMENT
- INCREASED RETINAL THICKENING WITH VITREOSCHISIS..I.E SEPERATION OF POSTERIOR VITREOUS PHASE IN TO TWO LAMELLAE AND THE POSTERIOR LAMELLA CAUSES FOCAL TRACTION ON THE FOVEA SUBSEQUENTLY TRD
- A TYPICAL CSR OF SMOKE STACK PATTERN THEY CAN BE 1 SEROUS RETINAL DETACHMENT WITH FLUID ACCUMULATION BETWEEN NEUROSENSORY RETINA AND RPE 2. SEROUS RD WITH PED ARTYPICAL CSR MAY 1 SMALL PEDS, 2. SICK RPE WITH PED 3.
- FOCAL AREA OF ENHANCED BACKSCATTER OR HIGH REFLECTIVITY UNDERLYING ILM THAT BLOCKS ALL CLINICAL REFLECTIONS FROM CHORIOD AND SCLERA
- THERE IS SEROUS RETINAL DETACHMENT OPTIC PIT IS CONDUIT CHANNEL FOR CSF FLUID ENTERING I TO THE SUBRETINAL SPACE…ALSO SHOWS SOME CYSTIC CAVITIES
- Fa shows telangiectasia in the early phase and late staning IT SHOWS HYPERPLASIA OF RPE EXTENDING IN TO THE INNER RETINAL LAYERS