A complete clinical review of idiopathic macular telangiectasia

Abstract

Idiopathic macular telangiectasia refers to a disease entity characterized by telangiectasia and alteration of the juxtafoveal capillary network. It can present uniocularly or binocularly and is subdivided into three groups which have varied appearances. Group I occurs in males which is easily identifiable and has macular edema. Group II has no sex predilection and difficult to distinguish by clinical examination and often requires the need of optical coherence tomography and angiographic modalities. Group III is not so common with its progressive nature and associated with neurological diseases. This article is aimed to provide complete details about idiopathic macular telangiectasia/idiopathic juxtafoveal telangiectasia/parafoveal telangiectasia including various groups, pathology, presentation, and management.

Introduction

Idiopathic macular telangiectasia describes a disease characterized by retinal capillary network incompetence, dilatations, and thinning which can be uniocular or binocular. Gass and Oyakawa[1] coined this disease and proposed a classification based on clinical angiographic features which were further updated by dividing the disease into three distinct groups with two subgroups in each group.

• Group I: Male predominance, congenital in nature with macular edema

• Group II: Bilateral presentation with foveal atrophy

• Group III: Progressive affection of capillary network and very rare.

In recent times, a newer simplified classification based on clinical and imaging modalities was proposed by Yannuzzi et al. who actually made the term idiopathic macular telangiectasia which was divided into two types: Type 1 is aneurismal and Type 2 is perifoveal.[2] In this review article, we primarily focus on the abovementioned two common types of IMT and the various staging system including the optical coherence tomography (OCT) staging system, Gass and Blondi,[1] and Sanchez staging system.

Aneurysmal Telangiectasia or Type 1 Idiopathic Macular Telangiectasia

Features

It is often unilateral and middle-aged males are commonly affected, this is considered the development form of idiopathic macular telangiectasia. This type is characterized by the presence of telangiectatic vessels with aneurismal dilatations and is predominantly seen temporal to fovea with the typical presence of macular edema [Figure 1a and b]. Retinal pigment abnormalities with subretinal neovascularization are also seen in Type 1 idiopathic macular telangiectasia.[1] Angiographic patterns seen include dilated vessels with prompt filling in the juxtafoveal region along with areas of capillary ischemia. Cystic or noncystic spaces in macula can be seen in cases with macular edema and OCT is a better tool in the evaluation of edema. OCT with advanced resolution can identify the presence of telangiectatic vessels as well and in general, the outer layers of retina will not be involved. Visual acuity of the patients is variable, and the most common cause of vision loss is macular edema/exudation and patients with worsening visual acuity and abnormal vascular pattern will require laser photocoagulation to stabilize. The pioneers Gass and Blodi[1] had found few patients with lesions away from fovea and so considered idiopathic macular telangiectasia to be a part of Coats’ disease spectrum.[3] The description given by Gass and Blondi for Type IB where the abovementioned features are present only within two clock hours of juxtafoveal region and good visual acuity, it has been included into the aneurysmal telangiectasia variant by Hirano Yannuzi et al.[4] stating the disease within two clock hours will eventually worsen.

Figure 1.

(a) Fundus photograph of patient showing features of retinal telangiectasis, aneurysmal dilatation with lipid exudation, (b) Angiogram image showing evidence of retinal telangiectasis with leakage

The common differential diagnosis of aneurismal idiopathic macular telangiectasia includes Coats’ disease, central/branch retinal vein occlusion, various retinopathies (metabolic including diabetic, radiation, anemic, inflammatory, and sickle cell disease), and retinal hemangioma.

Treatment

The treatment options for this variant include various options such as laser photocoagulation, intravitreal injection of steroids, and anti-vascular endothelial growth factor (VEGF) agents. Laser photocoagulation in the grid pattern often low-intensity burns in multiple settings has been proven effective in improving visual acuity and all dilated vessels need not be destroyed. The modality can be targeted toward leaking areas using indocyanine green angiography-guided photocoagulation and is found to be superior.[4] Intravitreal injection of triamcinolone acetonide reduces the macular edema due to its anti-inflammatory activity and membrane stabilization action and hence improved the visual acuity but the outcome is not long-lasting as within 3 months the visual acuity worsened and few had complications including elevated intraocular pressure.[5] Intravitreal anti-VEGF agents including the Food and Drug Administration approved ranibizumab and nonapproved bevacizumab have been found to be effective in reducing macular edema and significant improvement in visual acuity was noted. The effects due to anti-VEGF have longer duration than triamcinolone, however, large studies are needed to know the efficacy and safety of these agents for the treatment of aneurismal telangiectasia.[6]

Perifoveal Telangiectasia or Type 2 Idiopathic Macular Telangiectasia

This variant is the most common and often bilateral and can be asymmetrical where one eye alone will be involved initially. It affects both males and females equally often in their 50's which is acquired and no developmental factors involved.

Gass and Blondi subdivided the course of the disease into five stages.

Stage 1 patients are asymptomatic with subtle fundus and angiographic findings. Slight grayish retina was seen temporally with no obvious dilated vessels and angiography shows areas of late retinal staining with sparing of foveola.

Stage 2 patients have mild visual disturbance, especially in the central vision with metamorphopsia and/or paracentral scotoma. Graying of the parafoveal retina of size around 1500 microns exists.[7] It is often termed as occult macular telangiectasia as the vessels are not very prominent and angiographic evidence include vessel thickening with staining of walls in parafoveal region [Figure 2a and b].

Figure 2.

(a) Fundus photograph of the patient showing numerous retinal crystals around fovea with greying, (b) Corresponding angiogram image of the patient showing perifoveal capillary dilation and telangiectasis

Stage 3 is characterized by vision loss for the patients which in most cases is mild but gradually progressive in nature. Dilated venules located paracentrally draining into the telangiectatic vessels can be made out. There will be a network of proliferating vessels in the outer retina with variable amounts of leakage and staining. Edema and exudation in the macular region are not very prominent in this stage.

Stage 4 patient vision will be impaired and the typical features occur due to migration of retinal pigment epithelium (RPE) into the retina inside resulting in pigment clumps and can even form a stellate plaque resulting in pseudovitelli form lesions [Figure 3].[8]

Figure 3.

Colour fundus photograph of parafoveal telangiectasia Type IV with pigment clumps and stellate plaque

Stage 5 disease has marked and rapid vision loss due to the presence of subretinal neovascularization resulting in exudation, hemorrhage, and neurosensory retina detachment. There will be atrophy of the outer retina and neovascularization can reach up to it [Figure 4].[9] It is often associated with surrounding pigment epithelial abnormality. Angiographic features include classical early hyperfluorescence and its increases until it leaks in late phases. The size will be much smaller than choroidal neovascular membrane in age-related macular degeneration.

Figure 4.

Fundus photograph of parafoveal telangiectasia Type V with features of marked retinal atrophy and thinning

The stages 1–4 are described as nonproliferative stages and stage 5 is proliferative with sub-retinal neovascularization. Yellow-golden deposition of crystals along the temporal aspect of fovea has been seen in all stages without inconclusive clinical association.

The classical features of parafoveal telangiectasia are the absence of aneurysm, no exudation, and foveal atrophy in OCT. Report from Green et al. regarding the histopathological examination showed the presence of thickening of capillaries rather than telangiectasia with associated degeneration and loss of pericytes as well as endothelium. Inner retinal layer has edema both intra and extracellularly, retinal capillary proliferation is seen into outer retina.[10] Cases with subretinal neovascularization had deeper extension with retinochoroidal anastomosis and RPE migration into retina along telangiectatic vessels.[11]

Pathogenesis

The exact mechanism is not known clearly and retinal capillaries alteration such as thickening and increased permeability contributes to the disease process and progression. Outer retinal atrophy and degeneration ensue due to reduced nutrients which lead to photoreceptor damage and pigment migration causing vision loss. Subretinal neovascularization occurs due to proliferating capillaries going toward subretinal space and later leads to the anastomosis with choroidal vessels. Muller cells play a major role in the disease process and in patients without macular edema, photoreceptor atrophy is found to be the reason for vision loss.[12] The presence of intercellular and intracellular edema has been found within inner retinal layers which also leads to capillary dysfunction. Retinal capillary endothelial cell degeneration occurs due to the abnormality of parafoveal Muller cells which are like brain astrocytes.[13] Most cases of parafoveal telangiectasia are associated with crystalline deposits which are remnants of degenerated Muller cells. Subretinal neovascularization is similar to retinal angiomatous proliferation and often extends beneath retina. Reactive changes in the RPE will lead to the formation of pigmented plaques subretinally.

Other Features and Findings Apart from Fundus

OCT provides images of very thin sections of retina which is noninvasive and noncontact. The common findings in parafoveal telangiectasia include:

• Variable retinal thickness and often not related to leakage in angiography with minimal or no intraretinal edema[14]

• Foveal atrophy with disruption of the photoreceptor layer. More extensive in advanced disease[15]

• “Cystoid” are cyst-like structures commonly seen in the inner retinal layer which is of variable size and occurs due to progressive retinal tissue loss[16]

• Flattening of foveal pit[17]

• Few patients will have reflective dots in the nuclear layers of retina due to intraretinal neovascularization around foveola

• Retinal pigment epithelial plaques are observed as intraretinal hyperreflective lesions causing posterior shadowing as well.[18]

The abovementioned changes primarily occur due to Muller cell degenerations leading to parafoveal retinal capillary alterations, photoreceptors damage, and retinal cell loss. OCT provides an important aspect in understanding the disease process of parafoveal telangiectasia.[19,20,21]

Few OCT-based staging's has been proposed [Figure 5].

Figure 5.

(a and b) OCT images showing the presence of intraretinal clefts and atrophy of outer retinal layers. OCT: Optical coherence tomography

• Stage 1: No abnormality

• Stage 2: Disruption of photoreceptor in 20% of eyes with no cyst formation

• Stage 3: Disruption of photoreceptors with atrophy of outer retina in 85% of eyes with one or more cyst

• Stage 4: Hyperreflective plaque, foveal cyst, disruption of photoreceptor, and atrophy of outer retina are constant.

Sanchez proposed another staging,[17]

• Stage 1: Hyperreflective dots in inner retina which correspond to vessels in angiography

• Stage 2: The presence of cyst with Stage 1 findings and no evidence of retinal thickening

• Stage 3: Disruption with thickening of RPE choriocapillaris complex

• Stage 4: RPE proliferation which is seen as highly reflective area intraretinally adjacent to fovea

• Stage 5: Marked thickening of RPE/choriocapillaris complex which corresponds to subretinal neovascularization.

Confocal scanning laser ophthalmoscope, confocal blue reflectance, and confocal infrared reflectance help to identify even early lesions, progression assessment, and differentiating from other etiologies. However, confocal imaging systems may not replace angiography as finer details are not made out easily, combined modality of confocal and angiography will be useful.[22]

Macular pigment optical density in parafoveal telangiectasia typically shows marked central depletion of macular pigments commonly in an oval pattern which also corresponds to the hyperfluorescent area in angiography. This pattern is said to be typical for parafoveal telangiectasia and not common with other retinal diseases.[23] Fundus autofluorescence (FAF) is useful in detecting the disease earlier even before angiographic signs are visible.

Wong et al. proposed a categorization based on multiple imaging modalities including fluorescein angiography, FAF, OCT, and microperimetry.[24]

• Category 0: Normal results in all modalities

• Category 1: Slight increase in foveal autofluorescence

• Category 2: Category 1 with fundus and angiographic features without any cyst or atrophy

• Category 3: Marked increase in foveal autofluorescence with fundus and angiographic features including cyst or atrophy, reduced central retinal sensitivity in microperimetry

• Category 4: Varied patterns of altered FAF along with atrophy of outer retina and pigment clumping. Microperimetry shows the area of scotomas.

Treatment

The treatment option varies for nonproliferative forms and for subretinal neovascularization. It has been observed that vision loss is mainly contributed by macular edema and secondary vascular leakage is the factor leading to it. Laser photocoagulation using argon did not offer many benefits in most patients and even leads to worsening. It has been observed that laser photocoagulation leads to fibrosis and thinning of retina which accentuated the outer retinal atrophy primarily seen with the disease and so no clinical improvement was noted. Photodynamic therapy (PDT) with verteporfin has been tried in the aim to reduce the permeability of abnormal vessels, however, no significant anatomical or functional improvement of macular edema has been observed.[25] Intravitreal triamcinolone injection has been given and found to be beneficial in most patients but follow-up data were not available.[26,27] Wu et al. did a retrospective study and found no clinical improvement with intravitreal triamcinolone acetonide among nonproliferative variants.[28] Anti-VEGF's has been found to be beneficial parafoveal telangiectasia especially intravitreal injection of bevacizumab had reported improvement in visual acuity, reduction of macular edema, and decrease in angiographic leakage.[29] On follow-up, it has been observed visual acuity and central macular thickness improved but patients required repeated injections and also the effect of the treatment was less pronounced usually after two injections.[30] In a report, about two patients of parafoveal telangiectasia treated with intravitreal bevacizumab showed no significant improvement in visual acuity despite the reduction of vascular leakage and proposed that degeneration and progressive retinal atrophy leads to vision loss rather than just leakage.[6] A retrospective review also showed similar results where intravitreal bevacizumab had reduced the leakage but no significant improvement was noted in visual acuity and OCT,[31] similar findings were observed for pegaptanib.[32] The use of intravitreal anti-VEGF in parafoveal telangiectasia nonproliferative variant is not very defined and requires further studies before concluding its usefulness.

Proliferative form of idiopathic macular telangiectasia has poor prognosis and treatment also is not more beneficial in most cases than the nonproliferative form. Laser photocoagulation has been found useful in patients where the lesion is away from foveal center, however, visual recovery is guarded. PDT with verteporfin has been reported to reduce vascular leakage from subretinal neovascularization, but average of 2.5 PDT was required to stop leakage.[33] Transpupillary thermotherapy has showed a significant reduction in leakage and improvement of subretinal neovascularization and no change has been observed with the telangiectasia component.[34] Surgical intervention in the form of intravitreal anti-VEGF injection and mechanical removal has been studied, in which surgical removal had very poor postoperative outcomes. Intravitreal injection of bevacizumab or ranibizumab had showed reduction in the lesion but visual recovery is often questionable. Primary treatment with combined intravitreal anti-VEGF and PDT is found to more beneficial than anti-VEGF alone.[35]

Occlusive Idiopathic Macular Telangiectasia

This form is very rare and severe with features such as capillary telangiectasia, obliteration, and exudation. Vision loss is varied and not commonly studies because of its rarity.

Conclusion

Idiopathic macular telangiectasia or idiopathic juxtafoveal telangiectasia is an uncommon condition with subtle clinical findings and in many cases can lead to severe vision impairment. Aneurysmal telangiectasia is often easy to diagnosis with better prognosis than parafoveal telangiectasia. Subretinal neovascularization indicates poor prognosis and difficult management. Various treatment modalities including laser photocoagulation, Verteporfin PDT, anti-VEGF's, and surgical removal have been tried with variable outcome and requires further studies for guidelines regarding the management of these cases.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.