INDOCYANINE GREEN VIDEOANGIOGRAPHY

Moderator: DR. AJAY R KAMATHPresenter :DR. POOJA

• INTRODUCTION• SPECIAL PROPERTIES• ADVANTAGES• TECHNIQUE• CLINICAL APPLICATIONS

INTRODUCTION• 1957-Its first application in measuring CARDIAC OUTPUT

• 1970-Kogure et al. reported on intra-arterial ICG absorption of the choroid in monkeys.

• 1972-Flower and Hochheimer performed the first IV ICG angiography to image the human choroid.

• 1980-Hayashi and co-workers developed improved filter combination with sufficient sensitivity for near-infrared wavelength.

• 1989-Scheider and Schroedel introduced the use of scanning laser ophthalmoscope.

• 1992-Guyer introduced 1024 x 1024 line digital imaging system to produce high-resolution ICGA.

• Yannuzzi and co-workers described a 1024-line resolution system which was synthesized with appropriate flash synchronization and image storage capability ,permitting high-resolution ,long duration ICGA

SPECIAL PROPERTIES of ICGCHEMICAL PROPERTIES:

• Sterile, water-soluble tricarbocyanine dye• Empirical formula-C43H47N2NaO6S2

• Both lipophilic and hydrophilic• Na I is incorporated to create an ICG lyophilisate which

can be dissolved in water.

OPTICAL PROPERTIES :• Absorption spectrum -790 to 805 nm• Emission spectrum -770 to 880 nm(835nm)• RPE and Choroid absorbs 59-75% of blue green light

used in FA ,but 21-38% of near infrared light used in ICGA

• Better visualization through Serosanguinous fluid Shallow haemorrhage Pigment and lipid exudate

PHARMACOKINETICS :

• 98% protein bound(80% to globulins)• Less dye escapes from the fenestrated choroidal

vasculature allowing enhanced imaging• Excreted by Liver• Not detected in Kidneys, Lungs, CSF and does not

cross Placenta

TOXICITY :• Relatively safe drug• Adverse affects are less common than NaF• Mild reactions are Nausea Vomiting and Pruritus (0.15%)• Should be used with caution in patients with iodine allergy• Avoided in Uremic and liver disease patients• Classified as Cat-C drug for pregnant women

Advantages over FFA

• Study of choroidal vasculature otherwise prevented in FFA due to RPE blockage

• Near-infrared light utilized penetrates melanin, xanthophylls, exudates and sub-retinal blood.

• Infrared is scattered less than visible light, thus suitable in eyes with media opacities

• 98% ICG molecules bound to protein, thus remaining in the blood vessels.

TECHNIQUE• ICG should be dissolved in aqueous solvent and used within

10 hrs after preparation. Std.conc :25mg in 5ml solvent.(50mg,75mg)

• Rapid IV injection is followed by 5ml saline flush.• Images captured in 1min intervals till 5min,10-15min intervals

for 30-40 min• New TECHNIQUES : Real-time ICGA(30 frames/sec) Wide angle ICGA(160o of field ) Digital subtraction ICGA High-speed angiography

PHASES OF ICGA• Early phase (first 60 sec post

injection) :choroidal arteries

• Early mid phase (1-3 min) : choroidal veins and retinal vessels

• Late mid phase (3-15 min) : choroidal vessels fading but retinal vessels are still visible

• Late phase (14-45 min) : hypofluorescent choroidal vessels and gradual fading of diffuse hyperfluorescence

CLINICAL APPLICATIONS• ARMD• Idiopathic Polypoidal Choroidal Vasculopathy• Central Serous Chorioretinopathy• Choroidal Inflammatory disease Multiple Evanescent white dot syndrome Serpiginous Choroidopathy • Choroidal Tumours

ARMD• Hayashi and associates found that ICG videoangiography was

useful in detection of CNV,it revealed a well-defined neovascularization with occult CNV by FA.

• They also were the first to show that the leakage of ICG was slow compared to sodium fluorescein.

• Yannuzzi et al and Guyer et al studied ICGA of AMD patients and grouped them as follows

Depending on SIZE and DELINEATION

“HOT SPOT” “PLAQUE”Well defined

Poorly defined

Combination

• Macular Photocoagulation Study recognized two forms of OCCULT CNV:

(1) a fibrovascular pigment epithelial detachment (PED) (2) a late-phase leakage of an undetermined source (LLUS)

A pigment epithelium detachment (PED) (A, fluorescein angiography) with a well-delineated neovascular network located along the edges of the PED (B, indocyanine green angiography).

Fibrovascular pigment epithelium detachment (PED). FA demonstrates occult choroidal neovascularization with PED (A). In the early phases of (ICGA) a feeder vessel originating in the juxtapapillary area is clearly delineated (B, asterisk).

Late leakage of undetermined source (A, C). Indocyanine green angiography may clearly differentiate a subtype of occult choroidal neovascularization (B) from retinal angiomatous proliferation (D).

Advantages of ICG in CLASSIC CNV • ICGA improves visualization of the fine

structure of the neovascular network allowing the choroidal and retinal circulation to be distinguished.

• In patients with chronic AMD or those who

did not benefit from previous treatments with anti-VEGF, ICGA might better delineate a more mature stage of CNV. This has potential implications for therapeutic decision-making.

In FA image (A), the leakage of the dye from the lesion is evident, and obscures the boundaries of the neovascular network. (ICGA) (B), the limits of the neovascularization are much more visible

POLYPOIDAL CHOROIDAL VASCULOPATHY (PCV)

• It is a primary abnormality of the choroidal circulation characterized by an inner choroidal vascular network of vessels ending in an aneurysmal bulge or outward projection, visible clinically as a reddish-orange, spheroid, polyp-like structure

• ICGA has been used to detect and characterize the PCV abnormality with enhanced sensitivity and specificity.

• PCV is often misdiagnosed or confused with CSCR and with exudative age-related maculopathy

 

Late-phase FA(A) shows a neurosensory retinal detachment with multiple juxtapapillary “hot spots.” Early (B) and late (C) ICGA reveals the presence of juxtapapillary polypoidal choroidal vasculopathy

Late-phase FA image revealing type 1 occult choroidal neovascularization with a subfoveal pigment epithelium detachment (PED) (A). Early (B) and late (C) ICGA demonstrate a distinct network of vessels within the macular choroid ending with two hyperfluorescent “polyps.” 

CENTRAL SEROUS CHORIORETINOPATHY

• It is characterized by multifocal areas of choroidal hyperpermeability on ICGA, visible in the mid and late phases of the angiogram.

• ICG assessment of the location of these areas of hyperpermeability may be useful when considering treatment with verteporfin PDT.

ICG (B) reveals a more extensive alteration of the choriocapillaries, with multiple areas of hyper fluorescence

CHOROIDAL INFLAMMATORY DISEASE

It is a unilateral acute disease that affects young women, presenting with a transient, self-limiting visual loss.

Multiple Evanescent white dot syndrome

Late phases FA -only mild alterations at the level of the outer retina and RPE(A). Early phases ICGA (B) begin to reveal areas of hypofluorescence. size between 50 and 1000 µm, More evident in the mid to late phases of the angiogram (C).

• ICG allows better staging and identification of active lesions.• Active phase-Hypofluorescent areas with poorly defined

margins• Aggressive phase-late hyperfluorescence • Healed phase-Hypofluorescent areas with well defined

margins

Serpiginous Choroidopathy

CHOROIDAL TUMORS• Circumscribed choroidal hemangioma are benign

hamartomas that are more difficult to diagnose.• ICGA is the most useful study for demonstrating the intrinsic

vascular pattern of these tumors

Early-phase (ICGA) (49 seconds) - fine lacy vascular network of intrinsic vessels (C). Increasing hyperfluorescence(2min) is detected after injection: (D) Increasing hyperfluorescence(5min) (E) Of note, the margins of the tumor appear scalloped. (F) Late-phase ICGA study demonstrating hypofluorescence within the tumor (washout effect).

REFERENCES

• Ryan Retina• Diseases of Retina and Vitreous: Spaide• Yanoff • Kanski

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