Multimodal Imaging in Idiopathic Juxtafoveolar Retinal Telangiectasia

More than one imaging modality is often needed.

Jay Chhablani, MD • Igor Kozak, MD, PhD

In 1982, Gass and Oyakawa described idiopathic juxtafoveolar retinal telangiectasis (IJRT) as a unilateral or bilateral disease associated with incompetent retinal capillaries only in the perifoveal or juxtafoveal area.¹ In 1993, Gass et al. proposed revised classification and staging and a hypothesis of the pathogenesis of IJRT based largely on clinical examination and fluorescein angiography.²

Idiopathic juxtafoveolar retinal telangiectasis has been classified into three groups and various stages. Among the three groups, group 2 is the most common. Group 1 consists of extensive (1A) or focal (1B) aneurysmal telangiectasis in young men, with unilateral involvement and exudation and edema in the area of aneurysms.

Group 2 represents the most common form of IJRT, characterized by bilateral involvement and later onset than group 1. It is sub-grouped into 2A, acquired, and 2B, congenital. Group 3 is rare and usually bilateral, with extensive occlusion of the juxtapapillary network without exudation and associated with systemic diseases.²

In 2006, Yannuzzi et al. coined a new term for this disease based on newly recognized clinical and imaging characteristics: idiopathic macular telangiectasia (IMT).³ They proposed a new classification that does not include group 3 from the original classification.

Yannuzzi et al. retained the original classifications of type 1 (aneurysmal telangiectasia) and type 2 (perifoveal telangiectasia) in the new classification. They further subdivided type 2 into nonproliferative (exudation and foveal atrophy) and proliferative disease (subretinal neovascularization [SRN] or fibrosis).

The pathogenesis of this disease is still unknown; however, it has been proposed that impaired transport and/or storage of lutein and zeaxanthin, leading to central depletion of macular pigment, plays a role.¹

This article discusses imaging characteristics of IJRT group 2A and explains how recent imaging techniques have improved the understanding of this peculiar disease. Typical clinical findings in this subtype include juxtafoveolar area, predominantly of the temporal side, superficial retinal crystalline deposits, right-angled venules, and a loss of retinal transparency. As the disease progresses, intraretinal pigment migration and development of neovascular membranes occur.⁴

STAGING

Group 2A IJRT can be further divided into five stages. In stage 1, a slight loss of retinal transparency occurs, and the temporal juxtafoveolar area takes on a grayish appearance. The patient is asymptomatic.

Figure 1. Color photograph (1A) shows graying of the retina (arrow), along with pigment. Autofluorescence (1B) shows loss of foveal contour with a mild increase in autofluorescence (arrow) at the area corresponding to the area of leakage on fluorescein angiography (1C). Early-phase fluorescein angiography (1C) shows early leakage from telangiectatic vessels (arrow), demonstrating diffuse leakage in the late phase (arrow) (1D). Spectral-domain OCT (1E and 1F) images show thinning of the fovea with hyporeflective spaces and outer retinal damage (arrow).

In stage 2, a slight graying of the parafoveolar retina can be noted, with minimal telangiectatic vessels and crystals. Also in stage 2, patients may be asymptomatic or have minimal disturbances in central vision, such as metamorphopsia, blurred vision, or paracentral positive scotomas.

In stage 3, right-angled venules appear, and patients may complain of decreased vision. In stage 4, black retinal pigmented epithelial hyperplasia, or clumps around the right-angled venules, are seen. SRN and associated vision loss characterize stage 5 (Figure 1).²

IMAGING MODALITIES

Fluorescein Angiography

In the early stages, fluorescein angiography is required for the detection of capillary dilation. Telangiectatic vessels are seen, with increasing diffuse hyperfluorescence at a deeper level in the late phase but sparing the fovea. (Figure 1).⁵ On FA, SRN has typical features of classic neovascularization, demonstrating early hyperfluorescence, which increases and leaks in the late phases of the angiogram.

Absence of retinal pigment epithelium detachment and small size differentiate it from classic choroidal neovascularization secondary to age-related macular degeneration.⁶ In the advanced stages, contraction of fibrovascular proliferation causes retinal vascular distortion and dragging of neighboring venules and arterioles.

Autofluorescence

Disruption of foveal autofluorescence (AF) could be the earliest finding in IJRT 2A (Figure 1). The most frequent findings are complete loss of normal foveal hypoautofluorescence or an increase in foveal AF, or both. Retinal crystals and intraretinal pigment clumping show corresponding hypoautofluorescence due to blockage of physiological AF of the RPE (Figure 1).

Hyperautofluorescence around the pigment presents due to actively proliferating RPE cells. The parafoveal area may show an increase or decrease in autofluorescence. The hyperfluorescence seen in the late phase of FA in nontelangiectatic areas, which shows increased AF, could be due to a breakdown of the outer blood-retinal barrier. Changes in AF could be helpful in following the progression of the disease.⁷

Wong et al.⁸ introduced a severity scale on the basis of autofluorescence in IJRT 2A. The severity scale definitions are as follows:

► Severity 0: No evidence of disease (usually fellow eyes of affected individuals).

► Severity 1: Mild foveal autofluorescence changes without other abnormalities.

► Severity 2: Mild to moderate foveal hyperautofluorescence with angiographic abnormalities of macular telangiectasis.

► Severity 3: Moderate to marked foveal hyperautofluorescence with angiographic abnormalities and foveal atrophy documented on optical coherence tomography.

► Severity 4: Mixed patterns of fundus autofluorescence or marked thinning of the retina on OCT.

Optical Coherence Tomography

Optical coherence tomography imaging helps our understanding of the pathogenesis and natural history of IJRT and facilitates the follow-up of eyes with IJRT 2A, especially in the CNV stage. The OCT findings in IJRT type 2A include hyper-reflectivity or loss of the outer nuclear layer (ONL) corresponding to vessels, presence of hyporeflective intraretinal spaces, blunting of the foveal pit, intraretinal pigment migration, photoreceptor loss, and SRN/fibrosis (Figure 1).

Intraretinal cysts on OCT do not correspond to areas of hyperfluorescence on FA, unlike cystoid macular edema. OCT findings facilitate the detection of the cause of vision loss, including foveal atrophy, photoreceptor loss or SRN.^9,10

Sanchez et al. described OCT findings, which can help in classifying IJRT into each stage.¹⁰ In stage 1, highly reflective dots are present in the inner retina that correspond with microvessels on FA. In stage 2, hyporeflective intraretinal spaces occur in the absence of retinal thickening, as well as highly reflective dots in the retina.

In stage 3, an area of outer and inner retina with similar high reflectivity plus high-intensity RPE/choriocapillaris with evidence of disruption or thickening, or both, manifest. In stage 4, a highly reflective area nasal or temporal to the fovea in the inner or outer retinal layers is suggestive of RPE proliferation and migration.

In stage 5, a fusiform thickening and duplication of the highly reflective RPE/choriocapillaris complex occurs, corresponding to CNV.

Confocal Blue Reflectance Imaging

Confocal blue reflectance (CBR) imaging (at 488 nm), using the confocal scanning laser ophthalmoscope (Spectralis, Heidelberg Engineering, Heidelberg, Germany), is useful in the diagnosis of the early stages of IJFT 2A, as well as in following up these cases.

Increased CBR is noted around the fovea but not at the fovea. This parafoveal increased CBR has various patterns including focal, ring and oval. Increased CBR does not have any correlation with hyperfluorescence on FA or with any alterations of the outer retina on OCT.

The cause for increased CBR has been proposed to be the lack of macular pigment or change in retinal reflectance because of the disorganization of the neurosensory retina or the deposition of highly reflective material in the outer neurosensory layers.¹¹

Macular Pigment Optical Density

Depletion of macular pigment in IJRT 2A has been demonstrated on macular pigment optical density (MPOD), which shows a consistent unique abnormal pattern: a marked, oval-shaped depletion of macular pigment within the central retina, which corresponds to the late-phase hyperfluorescent areas on FA, with a surrounding ring of preserved MPOD at about 6° eccentricity. Macular pigment distribution may be useful in the diagnosis and follow-up of eyes with IJRT 2A.¹²

CONCLUSION

Autofluorescence and CBR could be highly useful for early diagnosis of IJRT 2A, while OCT and FA can facilitate the diagnosis of SRN and the evaluation of treatment response. Multimodal imaging has provided better insight into the pathogenesis of the disease and its natural history. With the help of advanced imaging, such as adaptive optics, understanding of this disease will further improve. RP

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