Indocyanine Green Videoangiography: Current Status

Protocol for Indocyanine Green Angiography

Indocyanine green (ICG) angiography was first approved by the Food and Drug Administration for human use in the 1956. Prior to its use in chorioretinal angiograms, ICG was used to measure blood flow and track cardiac output. It was only in 1969 when two researchers, Kyuga Kogure and Earl Choromokos from the University of Miami, first used ICG to create more accurate angiograms. In the following years, researchers were able to hone the underlying science of this new form of angiography. As time passed and technology advanced, the application of ICG in clinical practice became widespread. Today ICG is used to diagnose and monitor the progression of retinal and choroidal diseases affecting millions of individuals across the globe. ICG utilizes the injection of indocyanine green dye into a patient's bloodstream to visualize abnormalities of the choroid and retina by evaluating choroidal circulation. ICG angiography is useful in the diagnosis and management of occult choroidal neovascularization in age-related macular degeneration and may be used in other inflammatory conditions with central serous chorioretinopathy. ICG angiography offers advanced imaging for improved monitoring and treatment of a wide variety of choroidal and retinal diseases.

Clinicopathology of non-infectious choroiditis: evolution of its appraisal during the last 2-3 decades from "white dot syndromes" to precise classification

Choroidal imaging investigation techniques were very limited until 2–3 decades ago.

Fluorescein angiography (FA) was not suited for the analysis of the choroidal compartment and B-scan ultrasonography did not provide enough accuracy. It was on this background that a purely phenomenological approach was attempted to classify these choroiditis diseases by regrouping them under the vague potpourri term of “white dot syndromes”. With the availability of precise investigational modalities of choroidal inflammation or choroiditis-induced lesions, such as indocyanine green angiography (ICGA), spectral domain optical coherence tomography (SD-OCT) and enhanced depth imaging optical coherence tomography (EDI-OCT) it became possible to better classify these diseases based on clinico-pathological mechanisms rather than on purely phenomenological observation.

Recently OCT-angiography has implemented the armamentarium of diagnostic techniques possibly also contributing to the classification of choroidal inflammatory diseases.

Based on pioneering pragmatism, the aim of this article was to give a clear classification of non-infectious choroiditis. Thanks to new imaging investigations of the choroid, it is now possible to classify and understand the diverse clinicopathological mechanisms in the group of non-infectious choroiditis entities.

Utility of indocyanine green in the detection of radiologically silent hemangioblastomas: case report

Hemangioblastomas (HBs) are rare, benign, hypervascularized tumors. Fluorescent imaging with indocyanine green (ICG) can visualize tumor angioarchitecture. The authors report a case of multiple HBs involving two radiologically silent lesions only detected intraoperatively by ICG fluorescence. A 26-year-old woman presented with a cystic cerebellar mass on the tentorial surface of the left cerebellar hemisphere on MRI. A left paramedian suboccipital approach was performed to remove the mural nodule with the aid of ICG injection. The first injection, applied just prior to removing the nodule, highlighted the tumor and vessels. After resection, two new lesions, invisible on the preoperative MRI, surprisingly enhanced on fluorescent imaging 35 minutes after the ICG bolus. Both silent lesions were removed. Histological analysis of all three lesions revealed they were positive for HB. The main goal of this report is to hypothesize possible explanations about the mechanism that led to the behavior of the two silent lesions. Intraoperative ICG videoangiography was useful to understand the 3D angioarchitecture and HB flow patterns to perform a safe and complete resection in this case. Understanding the HB ultrastructure and pathophysiological mechanisms, in conjunction with the properties of ICG, may expand potential applications for their diagnosis and future treatments.

The role of multimodal imaging and vision function testing in ABCA4-related retinopathies and their relevance to future therapeutic interventions

The aim of this review article is to describe the specific features of Stargardt disease and ABCA4 retinopathies (ABCA4R) using multimodal imaging and functional testing and to highlight their relevance to potential therapeutic interventions. Standardised measures of tissue loss, tissue function and rate of change over time using formal structured deep phenotyping in Stargardt disease and ABCA4R are key in diagnosis, and prognosis as well as when selecting cohorts for therapeutic intervention. In addition, a meticulous documentation of natural history will be invaluable in the future to compare treated with untreated retinas. Despite the familiarity with the term Stargardt disease, this eponymous classification alone is unhelpful when evaluating ABCA4R, as the ABCA4 gene is associated with a number of phenotypes, and a range of severity. Multimodal imaging, psychophysical and electrophysiologic measurements are necessary in diagnosing and characterising these differing retinopathies. A wide range of retinal dystrophy phenotypes are seen in association with ABCA4 mutations. In this article, these will be referred to as ABCA4R. These different phenotypes and the existence of phenocopies present a significant challenge to the clinician. Careful phenotypic characterisation coupled with the genotype enables the clinician to provide an accurate diagnosis, associated inheritance pattern and information regarding prognosis and management. This is particularly relevant now for recruiting to therapeutic trials, and in the future when therapies become available. The importance of accurate genotype-phenotype correlation studies cannot be overemphasised. This approach together with segregation studies can be vital in the identification of causal mutations when variants in more than one gene are being considered as possible. In this article, we give an overview of the current imaging, psychophysical and electrophysiological investigations, as well as current therapeutic research trials for retinopathies associated with the ABCA4 gene.

Microvascular Changes in the Choriocapillaris of Diabetic Patients Without Retinopathy Investigated by Swept-Source OCT Angiography

Purpose

To investigate the microvascular changes in macular retina and choriocapillaris (CC) in diabetic eyes without retinopathy using swept-source optical coherence tomography angiography (SS-OCTA).

Methods

A commercial SS-OCTA system was used to collect 6 × 6-mm macular scans from patients. Three depth-resolved retinal slabs and a CC slab were segmented by a validated semiautomated algorithm. Retinal vessel area density, vessel skeleton density, and nonperfusion area were calculated on segmented retinal slabs. Foveal avascular zone was automatically measured based on en face image of the whole retinal layer. For CC quantification, the percentage of flow deficits (FD%) and the flow deficit (FD) sizes were measured. 

Results

Sixteen eyes from 16 diabetic patients without clinically detectable retinopathy and 16 eyes from 16 age-matched nondiabetic controls were included. There was no significant difference between the two groups in all retinal vessel quantitative parameters (all P > 0.05). However, the mean FD% and mean FD sizes were significantly increased in CC in the central 1.0-mm disk (P = 0.011 and P = 0.017, respectively), the central 1.5-mm rim (P = 0.003 and P = 0.009, respectively), the central 2.5-mm rim (P = 0.018 and P = 0.020, respectively), and the entire 5.0-mm disk (P = 0.009 and P = 0.008, respectively) in diabetic eyes compared with controls.

Conclusions

CC perfusion in the macula is decreased in diabetic patients without retinopathy as compared to age-matched normal controls. Decreased CC perfusion in the macula may be an early indicator of otherwise clinically undetectable diabetic vasculopathy.

Novel Classification of Early-stage Systemic Hypertensive Changes in Human Retina Based on OCTA Measurement of Choriocapillaris

The traditional classification of hypertensive retinopathy was based on the Keith-Wagener-Barker (KWB) grading, which is a subjective scaling system, and it is difficult to distinguish between the first and second grades. Retinal and choroidal vasculatures are affected by systemic hypertension, although retinal vasculature changes with age, axial length, intraocular pressure, and retinal diseases. It is necessary to establish a new objective method to assess hypertensive vascular changes. In the present study, we have examined the vasculature of the macular choriocapillaris in order to establish a new objective method to assess hypertensive vascular changes using optical coherence tomography angiography (OCTA). Choriocapillaris vessel density (VD), vessel length, and vessel diameter index in a 3 × 3 mm macular area were measured by OTCA in a total of 567 volunteers (361 healthy subjects and 206 subjects with systemic hypertension) who attended a basic health check-up. Ocular factors, systemic factors, and medications were evaluated. We detected significant differences in normative choriocapillaris vasculature between the left and right eyes in 53 healthy subjects and revealed correlations between age, intraocular pressure, axial length, and choriocapillaris vasculature in 308 healthy subjects. Normative foveal VD was correlated with age only and the efficiency was weak. The analysis of 206 right eyes (KWB grade 0, 159 eyes; grade 1, 35 eyes; and grade 2, 12 eyes) revealed that foveal VD was strongly correlated with KWB grade only (P < 0.001). This is the first report suggesting that OCTA for foveal choriocapillaris measurement by OCTA would might provide the advantage of evaluating be objective method for evaluating the progression of systemic hypertension.

Optical coherence tomography angiography

Optical coherence tomography (OCT) was one of the biggest advances in ophthalmic imaging. Building on that platform, OCT angiography (OCTA) provides depth resolved images of blood flow in the retina and choroid with levels of detail far exceeding that obtained with older forms of imaging. This new modality is challenging because of the need for new equipment and processing techniques, current limitations of imaging capability, and rapid advancements in both imaging and in our understanding of the imaging and applicable pathophysiology of the retina and choroid. These factors lead to a steep learning curve, even for those with a working understanding dye-based ocular angiography. All for a method of imaging that is a little more than 10 years old. This review begins with a historical account of the development of OCTA, and the methods used in OCTA, including signal processing, image generation, and display techniques. This forms the basis to understand what OCTA images show as well as how image artifacts arise. The anatomy and imaging of specific vascular layers of the eye are reviewed. The integration of OCTA in multimodal imaging in the evaluation of retinal vascular occlusive diseases, diabetic retinopathy, uveitis, inherited diseases, age-related macular degeneration, and disorders of the optic nerve is presented. OCTA is an exciting, disruptive technology. Its use is rapidly expanding in clinical practice as well as for research into the pathophysiology of diseases of the posterior pole.

Indocyanine Green Angiography (Icga) in Pathological Myopia

One hundred and fifty patients (300 eyes), mean age 49±15 years, with degenerative myopia underwent fluorescein and indocyanine green angiography (ICGA). Fluorescence of choroidal neovascularization (CNV) on ICGA was less evident than with fluorescein angiography (FA). FA revealed CNV in 98 eyes; ICGA showed CNV with different angiographic patterns in 82 eyes. ICGA permitted CNV diagnosis when retinal hemorrhages were present. ICGA allowed a more precise evaluation of lacquer cracks which appeared more numerous than the ones identified by FA. ICGA visualized the retrobulbar vasculature.

This study shows that ICGA has a useful role for diagnosing and managing pathological myopia.

Indocyanine Green Angiographic Findings in a Case of Punctate Inner Choroidopathy

Purpose

To report indocyanine green angiographic findings in a case of punctate inner choroidopathy.

Methods

Fundoscopy, fluorescein angiography and indocyanine green angiography were carried out on a 23-year-old woman who presented with features typical of punctate inner choroidopathy.

Results

Fundoscopy showed multiple small yellow lesions in the retinal pigment epithelium and inner choroid in both eyes and a subfoveal choroidal neovascular membrane in the left eye. The lesions showed early hyperfluorescence with mild leakage in the late phases of the fluorescein angiogram. On indocyanine green angiography, the lesions demonstrated obvious hypofluorescence in the early, mid and late phases.

Conclusions

The fluorescein and indocyanine green angiographic findings indicate that punctate inner choroidopathy affects the choriocapillaris as well as the retinal pigment epithelium and photoreceptors. However, it is still not known whether the primary pathology is in the retinal pigment epithelium, the photoreceptors or the choriocapillaris.

Use of indocyanine green in deep lamellar endothelial keratoplasty

A new technique using indocyanine green (ICG) during deep lamellar endothelial keratoplasty (DLEK) to stain the corneal stroma of the donor disk facilitated surgical placement of the disk in the host corneal opening created to match the donor disk. Two female patients, aged 82 and 77 years, had ICG staining of the donor corneal disk during DLEK for pseudophakic bullous keratopathy and Fuchs' corneal dystrophy. By 24 hours postoperatively, no ICG was detected clinically by biomicroscopy of the sutureless (no corneal sutures) lamellar transplanted corneas. This is the first report of the use of ICG during DLEK and the first intrastromal use of ICG in the human cornea. The use of ICG facilitated the DLEK procedure and appears to be safe for intraoperative use in the cornea.

Multimodal macula mapping: a new approach to study diseases of the macula

Multimodal macula mapping is presented as a combination of a variety of diagnostic tools and techniques to examine the macular region in order to obtain information on its structure and function in a clinical environment. Foundations of macular mapping are reviewed and discussed. New methodologies for multimodal macula mapping based on a combination of scanning laser angiography, retinal leakage analysis, retinal thickness analysis, and visual field testing are presented, demonstrating the potential of macula mapping. Other available detection devices are briefly reviewed considering their potential to be included and utilized in future developments of multimodal macula mapping. Multimodal macula mapping appears to offer unique perspectives and insights that are expected to contribute to improved diagnosis and better understanding of macular diseases.

Fluorescence properties and metabolic features of indocyanine green (ICG) as related to angiography

Indocyanine green (ICG) is a fluorescent dye that has been used for the imaging of retinal and choroidal vasculatures for more than 30 years. Its high molecular weight, specific metabolic features, and its infrared spectra make the specificity of the images obtained with this dye in ophthalmology. The focus of this paper is to review the basic properties of ICG and to show how some clinical features related to basic properties also depend on the instrumentation used to perform ICG angiography. Indocyanine green has a complex molecular structure that leads to amphiphilic properties, that is, both hydrophilic and lipophilic properties. These properties explain that a specific interaction with phospholipids influences the emission spectrum and the fluorescence yield of ICG. The composition of cell membranes mainly composed of phospholipid bilayers is consistent with a binding and/or a diffusion of ICG molecules observed on angiograms. Likewise, ICG can bind to the lipid component of miliary drusen, explaining their hyperfluorescence. A knowledge of ICG basic properties and interactions may allow a better understanding of angiograms performed with this dye.

Indocyanine green angiography in enlarged blind spot syndrome

PURPOSE

To report the indocyanine green angiography findings in a case of acute idiopathic blind spot enlargement syndrome.

METHOD

The patient underwent ophthalmologic examination with fluorescein angiography and indocyanine green angiography.

RESULTS

A monocular enlarged blind spot was found on automated perimetry; fluorescein angiography showed a hypofluorescent peripapillary atrophic area and indocyanine green angiography highlighted diffuse, small hypofluorescent spots scattered throughout the posterior pole. Visual field defects and indocyanine green angiography abnormalities resolved over 4 weeks.

CONCLUSION

Indocyanine green angiography in acute idiopathic blind spot enlargement syndrome showed many lesions not visible with fluorescein angiography, indicating a choroidal involvement reaching not only the peripapillary area but the entire posterior pole.

Schematic interpretation of indocyanine green angiography in posterior uveitis using a standard angiographic protocol

OBJECTIVE

Indocyanine green angiography (ICGA) detects fluorescence produced by the ICG molecule in the near infrared wave lengths showing choroidal vascular structures. Indocyanine green angiography may prove useful in the workup of uveitis with choroidal involvement. The authors' purpose was to test a standardized ICGA protocol for posterior uveitis to gather systematic and comparable data and to design a schematic approach for the interpretation of angiographic signs.

DESIGN

The proposed ICGA procedure included the search for preinjection fluorescence. In the early phase of ICGA (until +/- 2-3 minutes postinjection), posterior pole frames were taken to detect abnormalities in the retinal and choroidal arteriovenous circulation patterns. During the intermediate phase (12 +/- 3 minutes), posterior pole frames and eight 360 degrees panorama frames were taken to detect fluorescence abnormalities in the background impregnation of the choroid, the same sequence being repeated in the late phase (40 +/- 10 minutes). A cohort of more than 300 patients was analyzed in this standard fashion in 2 centers. PARTICIPANTS AND MAIN OUTCOME MEASURE: Determination of ICGA features and the proposed schematic approach for ICGA interpretation were based on the analysis of 109 cases of posterior uveitis with a well-determined diagnosis.

RESULTS

For uveitis, the intermediate and late phases of ICGA were found to yield the most valuable information showing either ICG hyperfluorescence or hypofluorescence or both. The ICG hyperfluorescence, always reflecting increased leakage or staining but not window defects because there is no pigment epithelium screen in ICGA, could originate either from increased leakage of the choriocapillaris, the large choroidal, or the retinal vessels. The characteristic ICG hypofluorescent dark dots indicating impairment of physiologic impregnation of the choroid could take at least five different patterns.

CONCLUSION

To date, ICGA features still are difficult to interpret. The proposed standardized ICGA protocol and schematized interpretation for posterior uveitis will help determine ICGA semiology for these disorders and might give new insights into their pathophysiology.

Choroidal abnormalities in birdshot chorioretinopathy: an indocyanine green angiography study

Birdshot chorioretinopathy is a rare inflammatory disorder with an insidious onset that can slowly progress to severe visual loss. The pathogenesis is unknown. This study used indocyanine green (ICG) angiography to investigate the degree of choroidal vascular involvement with progression of disease and to determine the nature of the birdshot lesions. Seven patients with birdshot chorioretinopathy had ICG angiography performed with a scanning laser ophthalmoscope at various stages of clinical disease. Results were compared with fluorescein fundal angiography (FFA). All large choroidal vessels appeared normal. The birdshot lesions were demonstrated with ICG but not with FFA and were represented by dark areas on ICG angiography. Typically these areas were bordered by large or medium-sized choroidal vessels and their appearance suggested small choroidal vessel hypoperfusion. In disease of recent onset, some lesions masked fluorescence from large underlying choroidal vessels possibly due to inflammatory choroidal infiltrates. In long-standing disease, the choroidal angioarchitecture was relatively normal within the birdshot lesions. This study of birdshot chorioretinopathy demonstrates abnormalities in the small choroidal vessels within the birdshot lesions. ICG angiography detects the birdshot lesions more readily than FFA and may be of benefit in assessing disease activity.

Choroidal capillary and venous congestion in central serous chorioretinopathy

PURPOSE

Abnormalities in choroidal perfusion have been hypothesized to be causative factors in central serous chorioretinopathy. This prospective study was performed to evaluate changes in the choroidal circulation in cases of central serous chorioretinopathy.

METHODS

In 32 consecutive patients with acute or chronic recurrent central serous chorioretinopathy, complete clinical ophthalmologic examinations, fluorescein angiography, and indocyanine green angiography with a scanning laser ophthalmoscope and a digital imaging system were performed.

RESULTS

All patients with acute and chronic recurrent central serous chorioretinopathy demonstrated a localized delay in arterial filling followed by choroidal hyperperfusion in the area of the damaged retinal pigment epithelium, frequently associated with dilated capillaries and dilated draining venules in one or more choroidal lobules. These changes corresponded to areas with pigment epithelial detachment or focal leakage from the retinal pigment epithelium found in fluorescein angiography. Furthermore, in some patients, localized choroidal ischemia could be observed in additional areas throughout the central fundus in both diseased eyes and normal fellow eyes.

CONCLUSIONS

Delayed arterial filling followed by capillary and venous hyperemia, angiographically appearing as capillary and venous congestion, can be observed frequently in eyes with central serous chorioretinopathy. The results suggested that capillary or venous congestion after ischemia in one or more choroidal lobules might be the reason for the choroidal hyperpermeability associated with central serous chorioretinopathy.

Indocyanine green angiographic findings in central serous chorioretinopathy

There has been great controversy about the pathogenesis of the focal changes in the retinal pigment epithelium (RPE) causing detachment of the neurosensory retina in central serous chorioretinopathy (CSC). This study was performed to evaluate changes in choroidal perfusion in 15 patients with CSC. Fluorescein and indocyanine green (ICG) angiography was performed in patients with acute or chronic recurrent CSC. In all patients delayed arterial filling followed by capillary and/or venous congestion, in some cases adjacent to ischemic areas, was found in the choroid. Leakage from the RPE in fluorescein angiography was only observed in those areas with choroidal capillary and/or venous congestion. The preliminary results suggest that venous congestion possibly in association with ischemia causes hyperpermeability of choroidal vessels already described in the literature.