OCT MACULA INTERPRETATION.

This presentation is mainly focused on the clinical diagnosis and interpretation of oct macula.This is presented on 4th year optometry as topic presentation.

1. OPTICAL COHERENCE TOMOGRAPHY ANUJA DHAKAL ADHIKARI B.OPTOMETRY , FINAL YEAR

2. LAYOUT INTRODUCTION HISTORY OF OCT TECHNICAL DESCRIPTION OF OCT PRINCIPLE OF OCT TYPES OF OCT MACULA OCT INTERPRETATIONS ADVANTAGES AND DISADVANTAGES ADVANCES IN OCT FURTHER RESEARCH ON OCT

3. INTRODUCTION OF OCT Optical coherence tomography (OCT) is a diagnostic, non-invasive, non-contact, transpupillary imaging system which provides high resolution cross-sectional images of anterior eye, the retina, vitreous and optic nerve. In vivo “optical biopsy” of the retina. Fast scanning rates and quick signal processing allows for image visualization in real time and at a video rate. OCT is also useful in other medical specialties, including otolaryngology, cardiology, gastroenterology, and vascular surgery.

4. HISTORY The use of OCT in posterior segment imaging was first reported by Huang et al in 1991. Since it became readily available for clinical use in the mid-1990s, OCT has revolutionized the way ophthalmologists diagnose and manage certain eye conditions. The OCT breakthrough was the capability to obtain high resolution histological images in vivo, in real time in non-invasive way and using harmless radiation (low power near infrared radiation, usually).

5. 1971 1996 1991 1993 2000 2002 2006 2012 2014 Concept of “seeing inside tissue” First OCT image of in-vitro retina First OCT image in-vivo retina First commercial ophthalmic OCT 2 nd gen of ophthalmic OCT 3 rd gen of stratus OCT Commercial SD-OCT Commercial Swept source OCT Commercial OCT-Angiography

6. TECHNICAL DESCRIPTION First and second generation OCT produces cross sectional images of the retina with an axial (depth) resolution of approx 12 – 15 micro meter, current commercial OCT offers a resolution of 8 – 10 micrometer – 10 x better than Ultrasound. Third generation OCT (OCT3) uses 500 axial scans taken in 1 second and has increased the resolution to 7 – 8 micrometer. Due to the interferometric measurements method,the axial resolution is defined by the light source , not the focusing optics .

7. The OCT two-dimensional scans are processed by a computer, then corrects for axial eye movement artifacts. The scans are then displayed in a false color representation scale in which warm colors (red to white) represent areas of high optical reflectivity and cool colors (blue to black) represent areas of minimal or no optical reflectivity.

8. PRINCIPLE OF OCT low coherence interferometry. The OCT setup is generally mounted with a Michelson interferometer, and can be divided in the following main parts: light source ( superluminescent diode) Scanning system L ight detector . These items define almost all crucial properties of the system.

9. OCT technique is based on Michelson interferometer to produce tomographic images. A light source, expressed in terms of it’s electrical field amplitude is introduced in the Michelson interferometer and is directed to the beamspliter . An interferometer splits light coming from a source into two separate paths and combines the light coming back from the two paths at the interferometer output. C onstructive interference Destructive interference

10. LIGHT SOURCE Uses broad-band light source . Four main desired characteristics: Wavelength Spectral bandwidth Intensity and stability. To biological tissue studies, the region known as “diagnostic window” is often used. This spectral region is between 800 nm and 1300 nm. Super L uminescent LED (SLED) : High intensities,High spectral stability & spectral band of 30 nm.

11. Lasers : A pplied in OCT research, most of them using a Ti:Sapphire laser & femtosecond laser which produces a broadband radiation. Lasers are a most flexible, about spectrum and intensity. In this type of fibers, nonlinear effects produces spectra large as 400 nm,allowing submicron of spatial resolutions. Swept source : Broadband laser with an intracavity optical narrowband filter.

12. SCANNING SYSTEM 1)TIME DOMAIN OCT Time domain oct uses a broadband light source ( infrared light source of 810nm ) and the reference arm contains a moving mirror that allows scanning of each depth position in the image pixel by pixel. 3 rd generation stratus oct is mainly used and it can’t picture 3D images. P athlength of the reference arm is translated longitudinally into time.

13. 2)FREQUENCY DOMAIN light source of 840 nm. The main advantage of Frequency Domain OCT it is that, once that a CCD based spectrometer is used, there is no need of any mechanical variation in time. The principle optical setup of FD OCT is similar to time domain oct,but the point detector is replaced by a spectrometer. All the depth information, the scattering profile, is encoded in the spectral interference pattern.

14. 3) SWEPT SOURCE light source of 1040 nm . Due to the source features the spectrum is acquired as a function of time& there is a relationship between time and wavelength. SS-OCT a single photo-detector is used (no gratings, no moving mirrors and CCDs). Mechanically the SS setup has no moving parts. 10 to 50 x quiker than traditional OCT and, due to SS be a laser, the SS intensity is greater than superluminescent LED, allows deeper tissue penetration.

15. OCT DEPTH RESOLUTION OCT depth resolution is determined by the wavelength band of the light source,and is unrelated to OCT detection technologies. Namely , OCT depth resolution (∆Z) can be shown with the following mathematical formula : ∆ Z = 0.44 × λ2/∆λ ( where λ is centre wavelength and ∆λ is wavelength range )

16. SPECKLE NOISE Speckle noise occurs when an object is scanned with coherent light, and is the most common cause of blurring to retinal layer boundaries on OCT B-scan images . Removal of speckle noise by multiple B-scan averaging.

17. A=1 BSCAN B=10 BSCANS C=100 BSCANS

18. DIFFERENCES FEATURES TD OCT FD OCT SPEED SLOWER THAN EYE MOVEMENTS FASTER THAN EYE MOVEMENTS REFERENCE MIRROR MOVING STATIONARY A-SCANS DIMENSION OF IMAGE GENERATED SEQUENTIALLY 2D IMAGES ENTIRE A-SCANS AT ONCE WITH SPECTROMETER ANALYSIS 3D IMAGES FRAME RATE RESOLUTION 20 10 MICRON DEPTH RESOLUTION UPTO 100 5 MICRON DEPTH RESOLUTION LINES PER FRAME 240 450-500 AXIAL RESOLUTION A-SCANS PER SECOND 10-20 400 SCANS 10-20 26,000 SCANS SCAN DIAMETER 7MM 8.3-10 MM

19. OCT IN OUR SETUP HEIDELBERG ENGINEERING SPECTRALIS OCT photo posted with patient’s and examiner’s consent

20. SPECTRALIS OCT I ntroduced in 2006 based on the Heidelberg Retina Angiogram 2 (HRA2). It incorporated two imaging techniques : confocal scanning laser ophthalmoscopy optical coherence tomography.

21. C onfocal scanning laser ophthalmoscopy(CSLO) O ffers a variety of laser sources providing different illumination wavelengths and detection schemes. CSLO imaging in the near infrared (IR) in the green and blue wavelength range,as well as fluorescence imaging modes of Angiography and for Autofluorescence . Optical coherence tomography C onfocal imaging creates a transversal image of the retina corresponding to the en-face plane of oct. U ses or utilizes the IR CSLO scans for Automatic motion tracking.

22. FEATURES OF SPECTRALIS OCT U ses Broad-band superluminescent Diode & Spectrometer. SLO has a center wavelength of 880 nm & spectral bandwidth of 40 nm resulting in an axial resolution of approximately 7 micronmeters in the eye. O ptical oputput = 1.2 mw. OCT frame rate is determined by scan density & camera’s read out time. Algorithm to combine multiple images= ART MEAN(Automatic real time Mean).

23. OCT SCANS PROTOCALS: MACULAR THICKNESS SCAN RETINAL NERVE FIBRE LAYER SCAN (RNFL SCAN) OPTIC NERVE HEAD SCAN AS-OCT ANGIO -OCT 6. EDI OCT

24. 1) MACULAR THICKNESS SCAN

25. LINE SCANNING OPHTHALMOSCOPE Thickness profile (tomogram). The image overlaid & colour coded over the fundus image. = slice navigators In dense scan only 49 line images are taken. ART= automatic real time scan HS=high speed scans

26. 2) ETDRS GRID Measures the thickness from internal limiting membrane to RPE. Consists of 3 circles outer ,inner and innermost circles.

27. 3)CROSS HAIR-LINE IMAGE OF THE MACULA Black and white or colour coded images. Image represent the cross hairline images of the macula taken in the horizontal direction,temporal to nasal.

28. 4) LINE RASTER SCANS Selective scanning profile . U sually taken at angle of 30 degrees.

29. WHICH EYE IS THIS ? Picture of Right eye as we can see the thick RNFL hyperreflective band exiting the retinal through optic nerve head

30. INDICATIONS FOR MACULAR OCT Detection of fluid within the retinal layers or under the retina (which may not be visible clinically ), M acular holes, pseudoholes , Epiretinal membranes ( ERMs ), V itreo -macular adhesion ( VMA ), V itreo -macular traction ( VMT ), E xudates Retinoschisis , R etinal detachment , Detachments of the retinal pigment epithelium D iabetic retinopathy ( DR ), A ge-related macular degeneration

31. MACULAR OCT CAN BE ANALYZED IN 5 DIFFERENT LAYERS AS: 1)PRE-RETINA 2)VITREORETINAL/VITREOMACULAR INTERFACE. 3)EPI-RETINA 4)RETINA 5)CHOROID

32. International Nomenclature for OCT Suggested the terms band, layer, and zone for the layers of the retina The term band refers to the three-dimensional structure of the retinal layers anatomically. The term zone describes those regions on OCT whose anatomical correlation is not clearly delineated. The RPE/Bruch’s complex is one of the layers described as zone as they are inseparable owing to interdigitation of cellular structure or tissue.

33. 1)PRE-RETINA Comprised of vitreous anterior to the retina. Non reflective dark spot in the oct. Faint-dots indicate noise formed due to electronic aberrations.

34. 2)VITREORETINAL/VITREOMACULAR INTERFACE. W ell defined due to the contrast between the non-reflective vitreous and the backscattering retina. The condensed vitreous overlying the ILM is called posterior vitreous face and are bound at their interface. fibronectin,laminin and other extracellular components that form a glue like matrix.

35. 3)EPI-RETINA A nterior surface of the retina. An epiretinal membrane (ERM) is a fibrocellular tissue,semi -translucent and proliferates on the surface of the ILM . Retinal glial and retinal pigment epithelial cells are the major components of ERM.Idiopathic ERMs is the most common presentation.

36. 4)RETINA A nterior boundary formed by hyperreflective band of ILM and bounded posteriorly by RPE. D ifferent intermediate layers of the neurosensory retina can be seen with different characteristic reflectivity patterns.

37. OUTER RETINA ( INTERNATIONAL NOMENCLATURE FOR OPTICAL COHERENCE TOMOGRAPHY PANEL ) 1)ELLIPSOID ZONE : Hyper reflective band ,formed mainly by the mitochondria within the outer portion of the inner segments of photoreceptors.Previously referred as IS/OS junction. 2)MYOID ZONE : Hyporeflective region between EZ to ELM.Hporeflectivity is attributed to the low packing density of the mitchondia in the myoids . 3)INTER-DIGITATION ZONE: Previously referred as COST or ROST. corresponds to the apices of the RPE cells that encase part of the cone outer segments . 4)RPE-BRUCH’S COMPLEX: 2 Hyper reflective bands separated by hyporeflective layer,often not separatable on normal conditions.

38. 5)CHOROID SS-OCT and EDI-OCT have enabled us to image choroid. which is seen as the multiple layers going from the innermost BM to the choriocapillaris, sattler layer, haller layer and a hyperreflective line indicating the choroido -scleral junction. To be discussed later on another presentation on OCT.

39. WHAT’S FOVEAL CUT?

40. Foveal cut is the area where the outer plexifom and retinal nerve fiber layer meet.

41. INTERPRETATIONS OF OCT

42. QUALITATIVE ANALYSIS MORPHOLOGICAL STUDIES Overall retinal changes,retinal outline. Vitreoretinal interface to choroid in new generation of oct. M ajor regions : Pre retinal area. Epi-retinal area. Intra-retinal area. Sub retinal area.

43. 2) REFLECTIVITY STUDIES Hyperreflectivity :Appear as White and is reflecting light. Hyporeflectivity : Appears as dark and caused due to absorption of light. Shadowing: Due to increased light absorption. Reverse shadowing : Due to loss of pigmented tisuue causing excessive light to be transmitted to outer layers.

44. NORMAL REFLECTIVITY OF STRUCTURES.

45. ABNORMAL PATHOLOGICAL REFLECTIVITY. 1) HIGH REFLECTIVITY SUPERFICIAL INNER REGION OUTER RETINA RPE -CHOROID Pre retinal membranes . Epi -retinal membranes. Cotton wool spots . Fibrosis. Haemorrhages . Haemorrhages . Hard exudates. Intraretinal haemorrhages . Calcification. CNVM . Hyperplasia. RPE atrophy. Naevus . Scarring. Fibrosis.

46. ABNORMAL PATHOLOGICAL REFLECTIVITY CONTD. 2) MEDIUM REFLECTIVITY. 3) LOW REFLECTIVITY Lipofuschin Deposits. Fluid(retinal edema , SRF , sub- RPE ) Cavities, Cysts. Detachments. Projected shadows.

47. ABNORMAL PATHOLOGICAL REFLECTIVITY CONTD. 3)SHADOWING SUPERFICIAL INTRARETINAL DEEP a)Dense : Micro and Macroaneurysms b)Imperfect Haemorrhages Cotton wool spots. a)Dense : Haemorrhages Sub-retinal deposits Neovascularization Scars b)Imperfect Laser spots Haemorrhages RPE atrophy. Naevus . Sub- epithelial parasitic cysts.

48. QUANTITATIVE ANALYSIS 1)RETINAL THICKNESS Retinal thickness is a reproducible and common quantitative measurement. The scan protocols, namely, 3D cube scan and radial scan generates the early treatment diabetic retinopathy study grid with the thickness values displayed in each sector . Displacement may depict thickness . Retinal thickness can be measured manually using the inbuilt caliper function.

49. Retinal thickness Values in microns, RPE-ILM . Retinal thickening Calculated value to the thickness minus the population mean for the variable under consideration. Center point( CP ) The intersection of the 6 radial scans of the fast macular thickness protocol of the oct. CPT ( center point thickness) Average of the thickness values for the 6 radial scans at their point of intersection. Center subfield(CS) Circular area of diameter 1 mm centered around the CP;128 thickness are made in this circular area in fast macula protocol. CSMT (central subfield mean thickness) Mean value of the 128 thickness value obtained in the CS. Absolute change in thickness Difference in the thickness between 2 measurements made at different time. Relative change in thickness Absolute change in thickness divided by the baseline thickness. Relative change in thicknening Absolute change in thickness (or thicknening ) divided by the baseline thickening. Definitions of commonly used landmarks and measurements on OCT

50. 2)RETINAL MAPS colour maps numerical value in map sector. A: Retinal nerve fiber layer, B: ganglion cell layer, C: inner plexiform layer, D: inner nuclear layer, E: outer plexiform layer + outer nuclear layer, F: photoreceptor inner segment, G: photoreceptor outer segment. Each retinal layer has high symmetry, but the ganglion cell layer and inner nuclear layer are slightly thinner temporally

51. WHAT TO LOOK FOR? 1)DETERMINE SCAN QUALITY 2)RATE OVERALL SCAN PROFILE 3)EVALUATE FOVEALPROFILE 4)IDENTIFY FOVEAL CUT 5)CARRY OUT STRUCTURAL ASSESMENT -OBSERVE ALTERATION OF LAYERS -IDENTIFY ADDITIONAL STRUCTURES PRE RETINAL EPI -RETINAL INTRA RETINAL SUB RETINAL SUB- RPE

52. Ten steps toward interpretation of an optical coherence tomography image 1) Determine the indication for the oct from the patient’s record,fundus pictures,angiograms,etc.Does the OCT image shown the area of interest? 2) Is the scan protocol used appropriate for the information required? 3) Is the scan quality good enough for analysis?Identity artifacts,other findings that could affect image quality 4) Use the macular Cube, 3D or volume scans for evaluation of the pathology,including the segment maps.colour or grayscale images are both adequate. 5) Look at the macular thickness map and ETDRS grid and get an idea as to the location of the pathology.Ensure that the overlay of the thickness map is centered on the fovea in the colour.SLO or IR image. 6) Evaluate each layer from the posterior vitreous to the chorio -scleral junction if visible,for deviation from the normal.The HD 5 line raster scans or line scans are preferable for this as they scan a precise location and gave a higher resolution. Grayscale images are preferable. 7) Classically the abnormality into one or more of the following:change in contour, change in thickness ,change in reflectivity, loss of tissue.look for thr location of the abnormality. Layers involved either primarily or as part of secondary effects. 8) Take measurements as appropriate in addition to the standard thickness measurements that are inbuilt in the protocals.In case of follow-up scans,use software to analyze change. 9) Advanced analysis such as en face OCT images can be generated in selected instances. 10) Look for the presence of known biomarkers before making the final diagnosis .

53. TERMINOLOGIES FOR ALTERATION OF STRUCTURES 1)Irregularity 2)Fragmentation 3)Rupture 4)Interruption 5)Depression 6)Elevation 7)Thinning 8)Thickening

54. CLINICAL CASES A)VITREOUS AND VITREO -MACULAR INTERFACE PATHOLOGIES

55. 1)VITREOUS HAEMORRHAGE

56. PRE-RETINAL SUB- HYALOID HAEMORRHAGE.IN THICK DENSE HAEMORRHAGES YOU CANNOT VISUALIZE THE RETINA POSTERIORLY . SHADOWING IS PRODUCED.INNER LAYERS CAN BE SEEN HYPERREFLECTIVE AND AS YOU GO MORE DEEPER THE RELECTIVITY DECREASES. PARTIAL VITREOUS DETACHMMENT CAN BE SEEN OVER THE MACULA.

57. 2)ASTEROID HYALOSIS

58. MULTIPLE HYPER REFLECTIVE SPOTS SEEN IN THE VITREOUS CAVITY . MOST OF THEM ARE PRESENTED IN CASES OF DIABETIC RETINOPATHY SO ALWAYS LOOK FOR VITREOUS MEMBRANES OR PULL ON THE RETINA.

59. 3)VITREOUS CELLS

60. FINER DETAILS WHICH COMPRISES OF FINE DOT LIKE HYPERREFLECTIVE STRUCTURES MULTIPLE AND DIFFUSE IN FASHION . MAINLY DUE TO INFLAMMATION.

61. 4)POSTERIOR VITREOUS DETACHMENT 1 3 2 4

62. 1)SUBTLE CHANGE ,THIN MEMBRANE WHICH IS PARTIALLY DETACHED FROM THE RETINA . 2)CYSTOID MACULAR EDEMA SECONDARY TO PVD.THIN MEMBRANE CAUSING VMT . 3) OVIOUS ON THE CLINICAL EXAMINATION BUT OCT WILL HELP YOU WITH THE ARCHITECTURE OF THE LESION . 4 ) COMPLETE PVD

63. 5) EPI -RETINAL MEMBRANE

64. CAN PRESENT IN VARIOUS WAYS,GLOBALLY ADHERENT MEMBRANE OVER THE ILM . PRESENTS AS CORRUGATED SURFACE THAT GIVES YOU THE CLUE ABOUT THE MEMBRANE .

65. 6) VITREOMACULAR TRACTION

66. VITREOMACULAR TRACTION LEADING TO FULL THICKNESS MACULAR HOLE,VMT MUST BE DIFFERENTIATED FROM VITREOMACULAR ADHESION IN WHICH VMA IS THE MACULAR ATTACHMENT OF THE VITREOUS CORTEX WITHIN 3 MM RADIUS OF THE FOVEA WITHOUT A CHANGE IN RETINAL MORPHOLOGY,WHEREAS IN VMT THERE IS PRESENCE OF RETINAL MORPHOLOGICAL CHANGES AS SEEN IN PICTURE A&B . C = FULL THICKNESS MACULAR HOLE.

67. B)INTRA-RETINAL PATHOLOGIES

68. 1)MACULAR EDEMA

69. Cystoid macular edema= circular spaces around outer plexifom layer,hyporeflective in nature inside retina and may be accompanied by sub retinal fluid . Causes are retinal vein occlusion, uveitis, or diabetes. It most commonly occurs after cataract surgery.

70. Diffuse edema resulting in cystoid intra-retinal spaces not necessarily complete thickening of the retina. Globally adherent membrane causing a diffuse macular edema . Obvious membrane pulling the retina resulting in Vitreo -macular traction.

71. 2)MACULAR HOLE Macular hole less than 400 microns without VMA . Impending macular hole with RPE elevation at foveal centre . Macular hole with complete PVD

72. 3)HARD EXUDATES

73. Hard exudates are seen as hyperreflective spots seen intraretinally at outerplexiform layer that produces shadowing on the deeper tissues . In picture A we can see some intra retinal and sub retinal fluids in this scan . causes:Diabetic retinopathy.Hypertensive retinopathy.Coat's disease.

74. 4)COTTON WOOL SPOTS

75. Focal or segmented areas of hyperreflectivity of the inner retinal layers in the acute phase . M ostly confined to retinal nerve fiber layer with sparig of the outer-retinal layers . C auses = ischaemic,immune and inflammatory conditions,infectious , embolic,neoplastic etc.

76. 5)INTRA-RETINAL HAEMORRHAGES

77. 6)RETINAL DEGENERATIONS Appreciable thinning of the outer nuclear layer (yellow arrows) The ellipsoid zone was seen to be attenuated in the parafoveal region

78. 7)INNER & OUTER RETINAL ATROPHY 1 2 1)atrophy of the outer retina usually in case of wet armd . 2)atrophy of the inner retina usually secondary to inflammatory cascade like endophthalmitis .

79. 8)RETINOSCHISIS

80. 8)RADIATION RETINOPATHY

81. Lymphoma treated with whole body radiation and bone marrow transplant 9 years prior.RR phenotypically results from microvascular occlusion and leaking capillaries between 6 and 36 months after radiation exposure . Macular edema is an initial sign of RR detected on OCT . There might be a presence of microaneurysma without frank diabetic retinopathy.

82. 9)PLAQUENIL TOXICITY Early photoreceptor and outer retinal damage spaceship sign

83. MEK inhibitor induced multifocal serous retinal detachments. Mitogen-activated protein kinase ( MEK ) inhibitors are a novel class of chemotherapeutic agents used to treat metastatic melanoma by inhibiting the MEK enzyme

84. C) SUB-RETINAL PATHOLOGIES

85. 1)ARMD

86. DRUSENS PRESENCE APPEARING AS UNDULATING AND ELEVATIONS IN THE HYPER REFLECTIVE BAND OF THE RPE WITH LESS REFLECTIVE MATERIAL BENEATH THEM . INNER RETINAL LAYERS REMAIN GENERALLY INTACT. DRUSENS ARE LOCATED UNDER OR OCCASSIONALLY ABOVE THE RPE . BRUCH’S MEMBRANE CAN BE VISIBLE. FOVEAL CONTOUR IS INTACT.

87. WET ARMD

88. GROSS INTRA-RETINAL EDEMA ,EXUDATES AND SUB-RETINAL HAEMORRHAGES . FLUID IN THE SUB RETINAL SPACE MAY BE PRESENT WHILE PRE RETINAL & INTRA RETINAL HAEMORRHAGES ARE LESS COMMON . FIBROVASCULAR PED MIGHT ALSO BE PRESENT,DISCIFORM SCARRING WITH SUB-RETINAL HYPERREFLECTIVE MATERIAL CAN BE SEEN.

89. GEOGRAPHIC ATROPHY There is loss of outer retinal layers including the RPE , EPIS line, COST line, ELM, and the outer nuclear layer. The Bruch's membrane and choroidal capillaris is visible due to the overlying outer retinal atrophy.

90. 2)CENTRAL SEROUS RETINOPATHY small PEDs and hyper-reflective, fibrinous sub-retinal fluid. RPE line is straight at the areas without serous PED .

91. 3)PIGMENT EPITHELIAL DETACHMENT OCT images of varying types of PED in the same patient with AMD. A) Drusenoid PED . B ) Serous PED . C ) Fibrovascular PED ( arrow) with overlying scant sub-retinal fluid and adjacent small serous PED .

92. 4)NEOVASCULARIZATION

93. PROLIFERATIVE DIABETIC RETINOPATHY …WHITE ARROW:hyperreflective loop extending from the optic disc into the vitreous cavity. YELLOW ARROW= neovascular membrane with the central epiretinal membrane . YELLOW ASTREIK : neovascular tractional membrane is visible temporally as a preretinal hyperreflective sheet. PINK ASTREIK = intraretinal fluid present.  GREEN ASTERICK =traction-induced subretinal FLUID

94. 5)OUTER RETINAL TUBULATIONS The hyperreflectivity of the shell, the relative hyporeflectivity of the inside of the tube and the location within the ONL . ovoid hyporeflective spac.present in age-related macular degenerationes .

95. 6)RETINAL DETACHMENT

96. 7) CHOROIDAL NEOVASCULAR MEMBRANE

97. NOVEL OPTICAL COHERENCE TOMOGRAPHY FINDINGS

98. ADVANTAGES OF OCT Non-invasive, Non-contact Improved lesion detection.delineation,differentiation from normal tissues. Improved lesion characterization. No ionization radiation: Can be performed in pregnancy(2 nd trimester onwards) & young children. More repeatability. Tissue sections comparable to histopathology sections.

99. LIMTATIONS OF OCT Media opacities can interfere with optimal imaging. Unable to show the details of ciliary body & posterior surface of the Iris. Landmarks such as scleral spur and Schwalbe’s line are not as clearly visible as UBM. Automatic demarcation of the optic disc borders by the machine may be inaccurate. As with most diagnostic tests, patient cooperation is a necessity. Artifacts. The quality of the image is also dependent on the operator of the machine. Always in co-relation.

100. ARTIFACTS ON OCT MIRROR ARTIFACTS : It occurs when the area of interest to be imaged crosses the zero delay line and results in an inverted image. 2) VIGNETTING : T his occurs when a part of the OCT beam is blocked by the iris and is characterized by a loss of signal over one side of the image.

101. 3) MISALIGNMENT : This occurs when the fovea is not properly aligned during a volumetric scan. 4)OUT OF RANGE ERROR: Outer retina/choroidal image is cut off because of improper positioning of the machine during image acquisition.

102. 5)BLINK ARTIFACT: Blink artifacts result in partial loss of data due to the momentary blockage of OCT image acquisition. Blink artifacts are easily recognized as black horizontal bars across the OCT image and macular map . 6)MOTION ARTIFACT: This occurs when there is movement of the eye during OCT scanning leading to distortion or double scanning of the same area . MULTIPLE OTHER ON OCT-A, TO BE DISCUSSED LATER

103. What is a clinically significant artifact? Any artifact resulting in automated segmentation errors of more than 10% of the actual ETDRS center subfield thickness (CST) is considered as clinically significant. Any artifact resulting in an error is more than 50 µm. This is based on a study of reproducibility in STRATUS TD OCT. Artifacts resulting in misdiagnosis of retinal thickening or thinning are noted as significant. Cutoffs are generated using published normative data for CIRRUS and SPECTRALIS and by defining retinal thickening or thinning as the mean ± 2 standard deviations .

104. 1) PED 2)RD 3)CSR 4) ARMD

105. 1) RETINOSCHISIS 2)MACULAR HOLE 3) ERM 4)RD

106. 1) PTMH 2)EXUDATES 3)RETINAL PUCKER 4)CME

107. 1) PVD 2)VITREOUS HAEMORRHAGE 3) ERM 4) FIBROUS DEGENERATION

108. 1)CME 2) ARMD 3) FOREIGN BODY 4) DR

109. 1) PED 2) DRUSENS 3) HAEMORRHAGES 4)RP

110. 1)HARD EXUDATES 2)COTTON WOOL SPOTS 3)RD 4)CME

111. RECENT ADVANCES

112. 1) OCT ANGIOGRAPHY Optical coherence tomography angiography (OCT-A) , non-invasive technique for imaging the microvasculature of the retina and the choroid . OCT-A technology uses laser light reflectance of the surface of moving red blood cells to accurately depict vessels through different segmented areas of the eye, thus eliminating the need for intravascular dyes. Spectral domain OCT (SD-OCT), with a wavelength of near 800nm; or a swept-source OCT (SS-OCT ), with wavelength, close to 1050nm . Currently, there are currently 4 main commercially available OCT-A devices: ZEISS Angioplex ™ OCT Optovue AngioVue ® Topcon® Heidelberg E ngineering ®

113. 2)VIS-OCT(OCT WITH VISIBLE LIGHT) S upercontinuum (SC) light source, which provides a smooth and powerful broadband spectrum with good spatial coherence within the visible spectral range . The axial resolution is improved more by switching to visible light illumination. The highest axial resolution achieved using this method was 12.2   μm , and the visible light spectrum covered 8 nm around 417 nm. Two major advantages: Improved resolution. Spectral imaging oximetry.

114. 3)OCT ELASTOGRAPHY (OCE) Optical coherence elastography (OCE) can provide clinically valuable information based on local measurements of tissue stiffness . The assumptions commonly used to interpret displacement and strain measurements in terms of tissue elasticity for static OCE and propagating wave modes in dynamic OCE are discussed with the ultimate focus on OCT system design for ophthalmic applications . Five dynamic OCE methods are considered in this comparative study . Each method is classified by a vibration source configuration : Crawling waves method Swept crawling wave Standing wave method Shear wave propagation Tone-burst propagation

115. 4)POLARIZATION SENSITIVE OCT(PS-OCT) PS-OCT measures the polarization state of light and is based on the fact that some tissues can change the polarization state of the probing light beam . Different mechanisms of Light–tissue interaction can cause such changes of the polarization state: birefringence, diattenuation , and depolarization . Anterior eye segment imaging with PS-OCT : keratoconus , Anterior-chamber angle. PS-OCT in retinal imaging: macular region , optic nerve head and peripheral retina.

116. 5)OPTICAL COHERENCE TOMOGRAPHY BLOOD FLOW OCT technique is capable of estimating functional characteristics of scanned tissue such as tissue blood flow using Doppler OCT and OCT angiography . T he optical frequency of light shifts when it scatters from moving red blood cells. The amount of the shift is related to flow velocity, and this information provides a noncontrast method to visualize and quantify retinal blood flow . While Doppler OCT provides data on total retinal blood flow, it is not sensitive enough to examine the microcirculation with low-velocity blood flow.

117. 6)High-Resolution OCT (High-Res OCT) 7)Full-Field OCT ( FFOCT ) and Dynamic FFOCT (D- FFOCT ) 8)Wide-Field and Ultrawide -Field OCT ( WF -OCT and UWF -OCT) 9)Hand-Held and Intraoperative OCT ( iOCT ) 10)At-Home OCT

118. EMERGING INNOVATIONS Photoacoustic ophthalmoscopy combined with OCT. Vertical-cavity surface emitting laser ( VCSEL ) technology .

119. 2)GLAUCOMA OVERVIEW MAP

120. SECTIONS OF THE REPORT PATIENT DATA FUNDUS IMAGE WITH RADIAL LINES OVERLYING THE OPTIC DISC TSNIT MAP OF RNFL TSNIT MAP OF NRR QUADRANT MAP – RNFL QUADRANT MAP- NRR POSTERIOR POLE RETINAL THICKNESS MAP POSTERIOR POLE GANGLION CELL THICKNESS MAP HEMISPHERE ASYMMETRY & AVERAGE THICKNESS

121. 1)PATIENT DATA

122. 2 ) FUNDUS IMAGE WITH RADIAL LINES OVERLYING THE OPTIC DISC

123. 3 ) TSNIT MAP OF RNFL

124. 4 ) TSNIT MAP OF NEURO RETINAL RIM

125. 5 & 6) QUADRANT MAP OF RNFL & NRR

126. 7 & 8) POSTERIOR POLE THICKNESS MAP OF RETINA AND GANGLION CELLS

127. 9) HEMISPHERE ASYMMETRY & AVERAGE THICKNESS

128. REFERENCES HANDBOOK OF RETINAL OCT,ELSEIVER 2013 OCT ATLAS- HANGAI BY HEIDELBERG ENGINEERING 2014 OPTICAL COHERENCE TOMOGRAPHY,KARGER 2014 EYEWIKI AAO AOA INTERNET RESOURCES

129. THANK YOU!