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FFA and ICG

FUNDUS ANGIOGRAPHY

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FFA and ICG

  1. 1. FLUORESCEIN ANGIOGRAPHY AND INDOCYANINE GREEN ANGIOGRAPHY • PRESENTER – Dr. KRATI GUPTA • MODERATOR – Dr. RONEL SOIBAM
  2. 2. FLUORESCEIN ANGIOGRAPHY • The study and diagnosis of retinal, macular and choroidal pathologic lesions have been greatly revolutionized with the advent of fundus fluorescein angiography (FFA). • From an initial laboratory tool, it has now become a useful diagnostic tool that has aided the diagnosis and monitoring of the treatment of retinal vascular and macular diseases. • Although the retina can be readily examined by direct and indirect ophthalmoscopy and slit-lamp bio microscopy, the fluorescein angiography provides a valuable addition to these techniques.
  3. 3. HISTORY OF FFA • The technique of using intravenous fluorescein to evaluate the ocular circulation was introduced 40 years ago by Mac Lean and Maumenee. • Chao and Flocks provided the earliest description of fluorescein angiography in 1958. • Finally, it was introduced into clinical use in 1961 by Novotny and Alvis, who demonstrated the photographic documentation of the fluorescein dynamics. • Over the last 3 decades advances have occurred in this sphere, digital imaging has made possible the generation of high resolution angiography of the retina and choroid.
  4. 4. INTRODUCTION • Luminescence: Emission of light from any source other than high temperature. • Fluorescence: Luminescence that is maintained only by continuous excitation. Property of certain molecules to emit light energy of longer wavelength when stimulated by a shorter wavelength. • Phosphorescence: Luminescence where the emission continues long after the excitation has stopped.
  5. 5. OUTER AND INNER RETINAL BLOOD BARRIER OUTER BLOOD–RETINAL BARRIER.  The major choroidal vessels are impermeable to both bound and free fluorescein.  The walls of the choriocapillaris contain fenestrations through which unbound molecules escape into the extravascular space.  It crosses Bruch membrane but on reaching the RPE are blocked by intercellular complexes termed tight junctions or zonula occludens.
  6. 6. INNER BLOOD–RETINAL BARRIER  It composed principally of the tight junctions between retinal capillary endothelial cells.  Across which neither bound nor free fluorescein can pass.  The basement membrane and pericytes play only a minor role in this regard.  Disruption of the blood–retinal barrier permits leakage of both bound and free fluorescein into the extravascular space.
  7. 7. PRINCIPLE OF FFA • Based on  Luminescence  Fluorescence  Phosphorescence • Two filters are used:  COBALT BLUE EXCITATION FILTER  YELLOW GREEN BARRIER FILTER .
  8. 8. EXCITATION FILTER  The dye absorbs light in the blue range of the visible spectrum with absorption peaking at 465 to 490 nm. The blue flash excites the unbound fluorescein within the blood vessels or the leaked out fluorescein.  The blue filter shields out all other light and allows through only the blue excitation light.  Structures containing fluorescein within the eye emit green-yellow light.  The blue light is reflected off of the fundus structures that do not have fluorescein.
  9. 9. BARRIER FILTER  The flourescein dye emits light from 500 to 600 nm with a maximum intensity at 520 to 530 nm (green-yellow).  The blue reflected light and green-yellow fluorescent light are directed back toward the film of the fundus camera.  Just in front of the film a filter is placed that allows the green-yellow fluorescent light through but keeps out the blue reflected light. Thus, even though the excitation and emission spectra are quite close, as long as suitably matched excitation and barrier filters are used, only substances capable of fluorescence are detected.
  10. 10. EXCITATION AND EMISSION SPECTRUM OF FLUORESCEIN
  11. 11. SODIUM FLUORESCEIN  Sodium fluorescein (C20H10O5Na2)  Orange red crystalline hydrocarbon.  Low molecular weight (376.27 Daltons).  Nontoxic, inexpensive, safe, alkaline solution.  Fluoresces at Blood pH (7.37-7.45).  Absorbs blue light (480-500 nm).  Emits yellow-green (500-600 nm) (Peak 525 nm).  80% bound to plasma protein and also with RBC.  Can’t pass through tight retinal barriers so allows study of retinal circulation
  12. 12. CLEARANCE • Complete removal from blood by kidneys and liver in 24-36 hrs. Metabolism • Sodium Fluorescein is metabolised to fluorescein glucuronide. • 60% of fluorescein is present in the form of metabolites 30 minutes after injection, and 80% is metabolized after 60 minutes. 96% of the active substance is glucuronized after five hours. Elimination • The plasma half-life of fluorescein is 11 minutes. Elimination is predominantly via the kidneys, but also via the liver and in the faeces. Renal clearance is 1.75 ml/minute/kg bodyweight. A dose of fluorescein is excreted almost completely within 36 hours of administration.
  13. 13. DOSASGE AND ADMINISTRATION Solutions containing 500 mg of fluorescein are available in vials of:  10 ml of 5% fluorescein  5 ml of 10% fluorescein  3 ml of 20% fluorescein solution (750 mg)  For children, the dose is calculated on the basis of 35mg for each 5kg. of body weight.  Dye is injected as a bolus into the vein of the patient's arm.
  14. 14. • With a greater volume the injection time increases, with a smaller volume, more fluorescein remains in the dead space between the arm and the heart. • Therefore, 5 ml of 10% solution (500 mg) fluorescein is generally preferred. • The venous dead space between the hand or the antecubital vein and the heart may be 5 to 10 ml, leading to sluggish or reduced flow of fluorescein into the central circulation. • The fluorescein can be flushed with 5 to 10 ml of normal saline. • An alternative is to elevate the patient’s arm above the level of the heart using an adjustable armrest, reducing the fluorescein transit time to the heart.
  15. 15. CONTRAINDICATIONS ABSOLUTE 1) Known allergy to iodine containing compounds. 2) H/O adverse reaction to FFA in the past. RELATIVE 1) Asthma 2) Hay fever 3) Renal failure 4) Hepatic failure 5) Cardiac disease – cardiac failure, Myocardial infarction 6) Previous mild reaction to dye. 7) Tonic-clonic seizures 6) Pregnancy ( especially 1st trimester)
  16. 16. USE IN PREGNANCYAND LACTATION • Controversial • Avoid angiography on patients who are pregnant, especially those in first trimester. • Fluorescein Crosses the placenta • Fluorescein is secreted in milk. • Has been done in pregnancy with no adverse effect • There have been no reports of fetal complications for fluorescein injection during pregnancy.
  17. 17. INTERACTIONS • Combination with beta-blockers may in rare cases cause lethal anaphylactic reactions. • Therefore, particularly in at-risk patients undergoing beta-blocker therapy for whom fluorescein angiography is essential- the procedure must be carried out under medical supervision, and with access to the necessary resuscitation equipment during the whole examination. • It should be born in mind that if such patients require resuscitation measures, they may not respond fully to the use of adrenaline. • The patient should be monitored for at least 30 minutes after completion of fluorescein angiography.
  18. 18. COMPLICATIONS MILD MODERATE SEVERE Staining of skin, sclera and mucous membrane Nausea and vomiting (10%) Respiratory- laryngeal edema, bronchospasm Stained secretion Tear, saliva Vasovagal response (1%) Circulatory shock, MI, cardiac arrest (<0.01%) Vision tinged with yellow Urtricaria (<1%) Generalized convulsion Orange-yellow urine fainting Skin necrosis Skin flushing, tingling lips pruritis periphlebitis Extravasation of dye and local tissue necrosis
  19. 19. EMERGENCY TRAY FOR FFA An emergency tray including such items as: • 0.1% epinephrine for intravenous or intramuscular use; • an antihistaminic, • soluble steroid, • aminophylline for IV use; • oxygen should always be available in the event of possible reaction to fluorescein injection.
  20. 20. TECHNIQUE AND EQUIPMENTS The materials needed for fluorescein angiography are as follows: 1. Fundus camera and auxiliary equipment 2. 23 gauge scalp vein needle 3. 5 ml syringe 4. Fluorescein solution 5. 20 gauge 1 ½ inch needle to draw the dye 6. Armrest for fluorescein injection 7. Tourniquet 8. Alcohol 9. Bandage 10. Standard emergency equipment
  21. 21. EQUIPMENT • The traditional fluorescein angiography unit has two 35 mm cameras, one for color fundus photography while the other (black & white) for fluorescein angiography. • Most fundus cameras take 30° photographs (magnification of 2.5X on a 35 mm film), which are adequate for a detailed study of posterior pole lesions especially macular diseases. • Many camera units provide variable magnification at 20, 30 and 50 degrees. • The 50° view is most useful for lesions involving a large area of the fundus.
  22. 22. PROCEDURE • Informed consent – explain the procedure to the patient. • Dilate patient’s pupil. • Fluorescein solution, scalp vein needle, 5 ml syringe and the emergency tray is prepared. • Check fundus camera for any fault. • Observe lens and fundus camera for any dust or opacity • Feed the machine with patient information – Name, MRD no, age, sex, clinical diagnosis etc.
  23. 23. • The patient is positioned and the camera aligned. • Color photography of both eyes. • Red free photograph of the posterior pole is taken. • Insert the scalp-vein needle, preferably at anticubital vein and inject the fluorescein dye 3ml of 20% solution in 5-10 seconds. • Simultaneously inject fluorescein dye and start Fluorescein mode in machine. • Once machine is set at Fluorescein mode timer will start and exciter and barrier filter will be activated.
  24. 24. • Oral administration at a dose of 30 mg/kg is an alternative if venous access cannot be obtained or is refused; a 5 ml vial of 10% (100 mg/ml) sodium fluorescein contains 500 mg, and pictures should be taken over 20–60 minutes following ingestion. • Images are taken at 1–2 second intervals initially to capture the critical early transit phases, beginning 5–10 seconds after injection, tapering frequency through subsequent phases. • Start fluorescein photograph 8 seconds after start of injection in young and after 10 seconds in older patients • Images may be captured as late as 10–20 minutes. • When photography is done, reassure the patient that all went well and remind him or her that the urine will be discolored for a day or so (24-36 hours). Make patient wait an additional 20 minutes for observation for possible reactions to fluorescein.
  25. 25. SEQUENCE OF PHOTOGRAPHS DURING FFA • Color photograph of Each eye. • Red free photograph of each eye • Room light to be kept dim • Activate Barrier and exciter filter , change the flash intensity and take control photographs. • Once dye is being injected set the machine at fluorescein mode and start the timer.
  26. 26. FFA PROVIDES THREE MAIN INFORMATION: 1. The flow characteristics in the blood vessels as the dye reaches and circulates through the retina and choroid . 2. It records fine details of the pigment epithelium and retinal circulation that may not otherwise be visible 3. Give a clear picture of the retinal vessels and assessment of their functional integrity
  27. 27. FLUORESCEIN PATHWAY • Arm-to-retina circulation time is 8-10 sec. • Normally 10-15 seconds elapse between dye injection and arrival of dye in the short ciliary arteries. • Choroidal circulation precedes retinal circulation by 1 second. • Transit of dye through the retinal circulation takes approximately 15 to 20 seconds.
  28. 28. ANGIOGRAPHIC PHASES Precise details of the choroidal circulation are typically not discernible, mainly because of rapid leakage of free fluorescein from the choriocapillaris. Melanin in the RPE cells also blocks choroidal fluorescence. The angiogram consists of the following overlapping phase: 1. Choroidal 2. Arterial 3. Arteriovenous 4. Venous 5. Late( recirculation) phase 6. The dark appearance of fovea.
  29. 29. CHOROIDAL PHASE  The choroidal (pre-arterial) phase typically occurs 9–15 seconds after dye injection .  It is longer in patients with poor general circulation.  It is characterized by patchy lobular filling of the choroid due to leakage of free fluorescein from the fenestrated choriocapillaris.
  30. 30. • A cilioretinal artery, if present, will fill at this time because it is derived from the posterior ciliary circulation.
  31. 31. ARTERIAL PHASE • The arterial phase starts about a second after the onset of choroidal fluorescence, and shows retinal arteriolar filling and the continuation of choroidal filling.
  32. 32. ARTERIOVENOUS PHASE • The arteriovenous (capillary) phase shows complete filling of the arteries and capillaries with early laminar flow in the veins in which the dye appears to line the venous wall leaving an axial hypofluorescent strip.
  33. 33. This phenomenon (laminar flow) reflects initial drainage from posterior pole capillaries filling the venous margins, as well as the small vessel velocity profile, with faster plasma flow adjacent to vessel walls where cellular concentration is lower.
  34. 34. VENOUS PHASE • Laminar venous flow progresses to complete filling, with late venous phase featuring reducing arterial fluorescence.
  35. 35. • Maximal peri foveal capillary filling is reached at around 20–25 seconds in patients with normal cardiovascular function, and the first pass of fluorescein circulation is generally completed by approximately 30 seconds.
  36. 36. LATE PHASE • The late (recirculation) phase demonstrates the effects of continuous recirculation, dilution and elimination of the dye. • With each succeeding wave, the intensity of fluorescence becomes weaker although the disc shows staining. • Fluorescein is absent from the retinal vasculature after about 10 minutes .
  37. 37. DARK APPEARANCE OF FOVEA The dark appearance of the fovea is caused by three factors:  Absence of blood vessels in the FAZ.  Blockage of background choroidal fluorescence due to the high density of xanthophyll at the fovea.  Blockage of background choroidal fluorescence by the RPE cells at the fovea, which are larger and contain more melanin and lipofuscin than else where in the retina.
  38. 38. PHASE TIME ( IN Secs) Choroidal phase 10 Arterial 10-12 Arterio venous 13 Early venous 14-15 Mid venous 16-17 Late venous 18-20 Late ( elimination) 5 MINS
  39. 39. KEY TERMINOLOGY IN FFA • Hyperfluorescence: An area of abnormally high fluorescence (due to increased density of the dye molecule) • Hypofluorescence: An area of abnormally poor fluorescence ( due to a paucity of dye molecules or due to masking of the fluorescence)
  40. 40. CAUSES OF HYPERFLOURESCENCE • AUTOFLUORESCENCE Autofluorescent compounds absorb blue light and emit yellow–green light in a similar fashion to fluorescein, but much more weakly. Autofluorescent lesions classically include:  Optic nerve head drusen.  Drusens.
  41. 41. AUTOFLOURESCENCE
  42. 42. • PSEUDO-FLUORESCENCE It refers to non-fluorescent reflected light visible prior to fluorescein injection; this passes through the filters due to the overlap of wavelengths passing through the excitation then the barrier filters. It is more evident when filters are wearing out. • INCREASED FLUORESCENCE It may be caused by; (a) Enhanced visualization of normal fluorescein density. (b) An increase in fluorescein content of tissues.
  43. 43. WINDOW DEFECT It is caused by atrophy or absence of the RPE as in :  Atrophic age-related macular degeneration.  A full-thickness macular hole.  RPE tears. This results in unmasking of normal background choroidal fluorescence, characterized by very early hyperfluorescence that increases in intensity and then fades without changing size or shape.
  44. 44. • POOLING  Pooling in an anatomical space occurs due to breakdown of the outer blood– retinal barrier.  A type of hyperfluorescence in which the dye accumulates within a closed space. (e.g. RPED)
  45. 45. • LEAKAGE Leakage of dye is characterized by fairly early hyperfluorescence, increasing with time in both area and intensity. It occurs as a result of breakdown of the inner blood–retinal barrier due to: Dysfunction or loss of existing vascular endothelial tight junctions as in  Diabetic retinopathy  Retinal vein occlusion  Cystoid macular oedema  Papilloedema. Primary absence of vascular endothelial tight junctions as  CNV  Proliferative diabetic retinopathy  Tumours  Coats disease.
  46. 46. LEAKAGE
  47. 47. • STAINING It is a late phenomenon consisting of the prolonged retention of dye in entities such as  Drusen,  Fibrous tissue,  Exposed sclera  Normal optic disc It is seen in the later phases of the angiogram, particularly after the dye has left the choroidal and retinal circulations.
  48. 48. HYPOFLOURESCENCE Reduction or absence of fluorescence may be due to: (a) Optical obstruction (masking or blockage) of normal fluorescein density (b) Inadequate perfusion of tissue (filling defect). • Masking of retinal fluorescence. Preretinal lesions such as blood will block all fluorescence • Masking of background choroidal fluorescence allows persistence of fluorescence from superficial retinal vessels:  Deeper retinal lesions, e.g. intraretinal haemorrhages, dense exudates.  Subretinal or sub-RPE lesions, e.g. blood  Increased density of the RPE, e.g. congenital hypertrophy  Choroidal lesions, e.g. naevi.
  49. 49. BLOCKED FLUORESCENCE
  50. 50. CAPILLARY NON-PERFUSION A type of hypofluorescence that results from non-filling of the retinal capillaries due to the anatomical or functional reasons.
  51. 51. • FILLING DEFECTS They may result from:  Vascular occlusion, which may involve the retinal arteries, veins or capillaries or the choroidal circulation.  Optic nerve head filling defects as in anterior ischaemic optic neuropathy.  Loss of the vascular bed as in myopic degeneration and choroideremia.
  52. 52. SYSTEMATIC APPROACH TO FLUORESCEIN ANGIOGRAM ANALYSIS A fluorescein angiogram should be interpreted methodically to optimize diagnostic accuracy. 1. Note the clinical findings, patient’s age and gender, before assessing the images. 2. Note whether images of right, left or both eyes have been taken. 3. Comment on any colour and red-free images and on any pre-injection demonstration of pseudo- or autofluorescence. 4. Looking at the post-injection images, indicate whether the overall timing of filling, especially arm-to-eye transit time, is normal.
  53. 53. SYSTEMATIC APPROACH TO FLUORESCEIN ANGIOGRAM ANALYSIS 5. Briefly scan through the sequence of images in time order for each eye in turn, concentrate on the eye with the greatest number of shots as this is likely to be the one with greater concern. Look for any characteristic major diagnostic features. 6. Go through the run for each eye in greater detail, provide a description of any other findings using the methodical consideration of the causes of hyper- and hypofluorescence set out above.
  54. 54. INDOCYANINE GREEN ANGIOGRAPHY • Indocyanine green (ICG) angiography (ICGA) is fast emerging as a popular and useful adjunct to the traditional fundus fluorescein angiography (FFA) in the diagnosis of macular, choroidal and outer retinal disorders. • This technique was introduced in ophthalmology in 1973 by Flower and Hochheimer. • FDA approved the ophthalmic use of ICG dye in 1975. • It remained largely unpopular owing mainly to technical difficulties. With the advent of videoangiogram recordings and the recognition of its potential in delineating occult choroidal neovascular membranes, the clinical use of ICGA has increased tremendously .
  55. 55. PRINCIPLES OF ICG  ICG fluorescence is only 1/25th that of fluorescein.  So modern digital ICGA uses high-sensitivity videoangiographic image capture by means of an appropriately adapted camera.  Both the excitation (805 nm) and emission (835 nm) filters are set at infrared wavelengths.  Alternatively, scanning laser ophthalmoscopy (SLO) systems provide high contrast images, with less scattering of light and fast image acquisition rates facilitating high quality ICG video.  The technique is similar to that of FA, but with an increased emphasis on the acquisition of later images (up to about 45 minutes) than with FA. A dose of 25–50 mg in 1–2 ml water for injection is used.
  56. 56. It also exhibits a phenomenon referred to as concentration quenching. After a period of increasing fluorescence with increasing serum concentration, that results in peak fluorescence, further increase in concentration, paradoxically leads to decreased fluorescence. This is thought to result from dimer formation.
  57. 57. INDOCYANINE GREEN  The indocyanine green (ICG) is a tricarbocyanine dye that comes packaged as a sterile lyophilized powder and is supplied with an aqueous solvent.  Molecular weight :774.97  It contains less than 5% sodium iodide (in order to increase its solubility).  It has a pH of 5.5 to 6.5 in the dissolved state, has limited stability, and hence must be used within 10 hours after reconstitution.  98% of the injected dye is bound to plasma proteins, with 80% being bound to globulins, especially alpha- 1 lipoproteins.
  58. 58. CLEARANCE  The dye is secreted unchanged by the liver into the bile.  There is no renal excretion of the dye  It does not cross the placenta.  The dye also has a high affinity for vascular endothelium, and hence persists in the large choroidal veins, long after injection.
  59. 59. ADVERSE EFFECTS  Nausea, vomiting are uncommon.  Anaphylaxis, approximately equal incidence to FA.  Serious reactions are exceptionally rare.  ICG contains iodide and so should not be given to patients allergic to iodine or possibly shellfish.  iodine-free preparations such as infracyanine green are available.
  60. 60. CONTRAINDICATIONS  ICGA is relatively contraindicated in liver disease (excretion is hepatic)  In patients with a history of a severe reaction to any allergen.  moderate or severe asthma  significant cardiac disease.  Its safety in pregnancy has not been established.
  61. 61. TECHNIQUE AND DOSAGE  The technique is similar to that of FA.  There is an increased emphasis on the acquisition of later images (up to about 45 minutes) than with FA  A dose of 25–50 mg in 1–2 ml water for injection is used.
  62. 62. PHASES OF ICGA  Early – up to 60 seconds post-injection  Early mid-phase – 1–3 minutes  Late mid-phase –3–15 minutes  Late phase – 15–45 minute
  63. 63. EARLY PHASE (UP TO 60 SECONDS POST-INJECTION) • showing prominent choroidal arteries and poor early perfusion of the ‘choroidal watershed’ zone adjacent to the disc.
  64. 64. EARLY MID-PHASE (1–3 MINUTES) • showing greater prominence of choroidal veins as well as retinal vessels.
  65. 65. LATE MID-PHASE (3–15 MINUTES) • showing fading of choroidal vessels but retinal vessels are still visible; diffuse tissue staining is also present.
  66. 66. LATE PHASE (15–45 MINUTES) • showing hypofluorescent choroidal vessels and gradual fading of diffuse hyperfluorescence
  67. 67. HYPERFLOURESCENE  A window defect similar to those seen with FA.  Leakage from retinal or choroidal vessels the optic nerve head or the RPE gives rise to tissue staining or to pooling.  Abnormal retinal or choroidal vessels with an anomalous morphology exhibiting greater fluorescence than normal.
  68. 68. HYPOFLOURECENCE  Blockage (masking) of fluorescence.  Pigment and blood are self-evident causes, but fibrosis, infiltrate, exudate and serous fluid also block fluorescence.  A particular phenomenon to note is that in contrast to its FA appearance, a pigment epithelial detachment appears predominantly hypofluorescent on ICGA.  Filling defect due to obstruction or loss of choroidal or retinal circulation.
  69. 69. INDICATIONS OF ICGA  Polypoidal choroidal vasculopathy (PCV): ICGA is far superior to FA for the imaging of PCV.  Exudative age-related macular degeneration (AMD): Conventional FA remains the primary method of assessment, but ICGA can be a useful adjunct, particularly if PCV is suspected.  Chronic central serous chorioretinopathy often difficult to interpret areas of leakage on FA. ICGA shows choroidal leakage and the presence of dilated choroidal vessels.  Posterior uveitis. ICGA can provide useful information beyond that available from FA in relation to diagnosis and the extent of disease involvement.  Choroidal tumors may be imaged effectively but ICGA is inferior to clinical assessment for diagnosis.  Breaks in Bruch membrane such as lacquer cracks and angioid streaks are more effectively defined on ICGA than FA  If FA is contraindicated.
  70. 70. ADVANTAGES OF ICGA OVER FFA  FA is an excellent method of studying the retinal circulation, it is of limited use in delineating the choroidal vasculature, due to masking by the RPE.  In contrast, the near-infrared light utilized in indocyanine green angiography (ICGA) penetrates ocular pigments such as melanin and xanthophyll, as well as exudate and thin layers of subretinal blood, making this technique eminently suitable.  ICGA can be used even when the ocular media are too hazy for FFA. This is due to the phenomenon of Rayleigh scatter .  ICG fluorescence can be imaged even in the presence of considerable blood, due to the phenomenon of Mie or forward scatter.
  71. 71.  The peak absorption of ICG coincides with the emission spectrum of diode laser, which allows the selective ablation of chorioretinal lesions using ICG dye-enhanced laser photocoagulation wherein a target tissue containing ICG is exposed to the diode laser beam.  Photophobic patients tolerate ICGA better than FFA.  ICGA accurately measures the size of an occult choroidal neovascular membrane(CNVM).
  72. 72. LIMITATIONS OF ICGA  The choriocapillaris cannot be imaged separately with ICGA since their average cross-sectional diameter (21 μm) is much smaller than that of their feeding and draining vessels, and hence the fluorescence of the former cannot be differentiated from that arising from the latter.  The phenomenon of Mie scatter also masks the unfilled retinal vessels that cannot be visualized well in low speed angiography systems.  Bright areas do not necessarily signify dye leakage due to the phenomenon of additive fluorescence  ICGA is poorer than FFA in the imaging of classic CNVM since the early hyper fluorescence of the CNVM is overwhelmed by the intense background choroidal filling.  Although superior to FFA in the imaging of occult CNVM, ICGA may underestimate the size of the CNVM.
  73. 73. Fundus fluorescein angiography ICG angiography For retinal circulation For choroidal circulation Dye used – sodium fluorescein Dye used – indocyanin green 80% plasma protein bound and low MW 98% plasma protein bound and high MW Light of visible spectrum used Infrared spectrum of light used Blue green filters used Infrared filters used More side effects Less side effects
  74. 74. RECENT ADVANCES IN INDOCYANINE GREEN ANGIOGRAPHY Wide-angle angiography: This is carried out by performing ICGA with the aid of wide angle contact lenses, such as Volk SuperQuad and a traditional Topcon fundus camera. This allows real-time imaging of a wide field of the choroidal circulation up to 160 degrees of field of view. Overlay technique: This technique allows lesion on one image to be traced on to another color or red-free image. Digital stereo imaging: Elevated lesions such as PEDs can be better imaged in this way. ICG as a photo sensitizer: It is considered to be a cheaper alternative to vertoporfin in photodynamic therapy of neovascular AMD& other disorders . Digital subtraction ICGA: It uses digital subtraction of sequentially acquired ICG images along with pseudo color imaging. It shows occult CNVM in greater detail and within a shorter time than conventional ICGA.
  75. 75. FUTURE APPLICATIONS OF INDOCYANINE GREEN ANGIOGRAPHY In the future, ICGA is expected to play a more important and wider role especially in the management of macular disorders.  Identifying subclinical neovascular lesions in the other eye of patients with AMD. There are several reports that mention that 10% of such eyes with no clinical or fluorescein angiographic evidence of an exudative process harbor plaques of neovascularization evident on ICGA.  ICG-guided feeder vessel photocoagulation: SLO high-speed ICGA can adequately image the feeding vessels of the CNVM which are 0.5 to 3 mm in length and are believed to lie in the Sattler’s layer of the choroid.
  76. 76. HEIDELBERG RETINAL ANGIOGRAPH • HRA2 a product of Heidelberg Engineering GmbH, Germany. • Preferred imaging device of retinal specialist in research centers and apex institutes. • Unique feature is dynamic high speed angiography and higher resolution.
  77. 77.  16 frames per second motion images  Also called as Confocal scanning laser ophthalmoscope  It is used in the following basic modes like • Fluorescein angiography (FA mode) 488nm • ICGA mode 790nm • Red free reflection 488nm • Infrared reflection 820n
  78. 78. SCHEMATIC STRUCTURE OF CSLO
  79. 79. SALIENT FEATURES OF HRA • Spherical refractive error of –12 to +30D can be compensated by setting the control dial. • In addition, internal myopic lens of –6 or –12D spherical correction can be set without using any external lenses. • HRA2 field of view are 30, 20 and 15 degrees • Simultaneous mode – e.g. both FA and ICG images of identical areas can be captured and stored. • Composite mode – the software of HRA2 automatically evaluate the images and connects them to one another, creating large composite image ( 100 or 80 degrees) .
  80. 80. • Fixation mode – ensure the patient’s visual fixation is stable there are both internal and external fixation lights. • Wide angle objective – width of field is broadened to 57 degrees for examining the peripheral fundus. Can be used in composite mode also. • Automatic real time module (ART) – software detects and corrects for eye movements. Helpful in imaging autofluorescenes, cloudy media or high astigmatism. • Examining the anterior segment – to perform iris angiography by setting optics control to +40D and adjust the distance between camera and eye to optimize the focus. • Stereoscopic viewing – helpful in examining the 3 dimensional images. • Components of analytical software – converted into other image modes. Biometric functions also available
  81. 81. ADVANTAGES  Higher resolution and contrast  Used in imaging FFA, ICG and autofluorescene
  82. 82. THANK YOU

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