Introduction

Idiopathic parafoveal telangiectasia (IPT) is a rare retinal disorder characterized by a dilated retinal capillary network at the foveal area.¹ Gass and Blodi² have classified IPT into three types. Type 2 IPT is the most common one. It appears at the 5th and 6th decade of life with complaints of progressive decrease in the visual acuity and metamorphopsia.³ In 1/3 of patients, diabetes mellitus or impaired glucose tolerance is detected.⁴ The dilated parafoveal capillary network in fluorescein angiography (FA) and especially the diffuse leakage at the late phase on the temporal area of the fovea are the typical findings of IPT.⁵ Vascular endothelial growth factor (VEGF) has been shown to have an important role in the development of abnormal vessels and vascular permeability. It has been demonstrated that inhibition of VEGF intravitreally prevents neovascularization and stabilizes the blood-retinal barrier.⁶ Recently, it has been thought that VEGF has the main role in the pathogenesis of IPT.⁷ In this case, we aimed to compare the effects of intravitreal bevacizumab (IVB) and intravitreal triamcinolone acetonide (IVTA) in the treatment of IPT. 

Case Report

A 50-year-old man was admitted to our clinic with complaint of decreased vision, especially in the right eye. The decrease of vision started 6 months ago and got progressively worse. From the patient history, we learned that he has a well-controlled diabetes mellitus for 6 years. The best-corrected visual acuities (BCVA) were 5/100 and 5/10 on the right and left eye, respectively. There were no any particular findings in the examination of the anterior segment. The intraocular pressures were in normal limits in both eyes. Fundus examination revealed telangiectatic vessels in both maculae, especially in the temporal area of the fovea (Figure 1). Also decrement in the foveal brightness was detected. The fundus angiogram showed hyperfluorescence due to telangiectatic vessels in the early phase of FA and macular edema, especially in the right eye, in the late phase of the FA (Figure 2, 3). Although the resolution of optical coherence tomography (OCT) was not very high, it revealed relatively normal anatomy of the fovea, despite the hyperfluorescence detected on FA (Figure 4). The patient with these findings was diagnosed as type 2A IPT. As treatment option, IVTA was planned on the right eye and IVB on the left eye. Informed consent was taken from the patient for the treatment procedure. Firstly, in operating room conditions, after cleaning the fornices in the right eye with 5% betadine, 4 mg-0.1 cc of triamcinolone acetonide was injected intravitreally with a 27 gauge needle in the inferior temporal quadrant 4 mm from the pars plana. 24 hours later, in the same conditions, 1.25 mg-0.05 cc of bevacizumab was injected in the left eye. As prophylaxis, an antibiotic from third-generation fluoroquinolones (ofloxacine) was given four times a day for a week. The patient was evaluated on the first day, first week, first month, and the third month after the injections. No complications related to the injections were observed on these visits. On the first-week visit, the BCVA was 5/10 on the right eye and 10/10 on the left eye. The visual acuities were the same on the first- and third-month follow-up visits. On control FA, there was significant decrement of fluorescence in the early phase especially in the left eye and also decrement in the leakage in the late phase (Figure 5). The patient did not need any additional treatment during this time period.

Discussion

In 1993, IPT has been classified into three groups by Gass and Blodi. The classification and staging of the disease are basically made on FA findings. Group 1A refers to unilateral congenital parafoveal telangiectasis with telangiectatic capillaries temporal to the fovea; group 1B -unilateral, idiopathic, focal juxtafoveal telangiectasis with a small focal area of incompetent capillaries next to the foveal avascular zone; group 2A - bilateral idiopathic acquired parafoveal telangiectasis with retinal thickening temporal to the fovea, right-angled venules, retinal pigment epithelial (RPE) hyperplastic plaques, subretinal neovascularization and crystalline deposits; group 2B - juvenile occult familial IPT; group 3A- occlusive IPT with casual visual loss due to obliteration of perifoveal capillaries; and group 3B is occlusive IPT associated with central nervous system vasculopathy. Moreover, Gass and Blodi divided the development of group 2A into 5 stages. Stage 1 is usually found on FA, with staining and leakage at the level of the RPE. Stage 2 is characterized by the loss of transparency of the parafoveal retina with capillary telangiectasis visible only by FA. In stage 3, dilated right-angled venules develop and FA demonstrates unusual capillary dilatation and staining in the outer retina. In stage 4, stellate foci of superficial retinal pigmentation due to migrating RPE cells are observed along the right-angled venules. In stage 5, there is an evidence of retinal neovascularization or exudation from new vessels in the subretinal space. The visual prognosis is poor because of the foveal atrophy due to retinal edema, central scar on the RPE and occasionally due to the development of the choroidal neovascularization (CNV).2

In IPT, vascular changes occur in the deep retinal capillary network, leading to intraretinal neovascularization with an unknown mechanism. There is no capillary ischaemia or inflammation. The vasogenic cellular mechanism may be the provoking factor for progressive degeneration of the endothelial cells of retinal capillaries.8

Intravitreal application of steroids in the treatment of macular edema is useful because of some biological effects. Steroids inhibit the biosynthesis of leukotrienes and prostaglandins. They stabilize the blood-retinal barrier and also downregulate the synthesis of VEGF.1 Due to these effects of steroids, they have been used also in the treatment of macular edema seen in IPT. Alldredge and Garretson9, in a case with type 2 IPT, during an 8-week follow-up after injection of 4 mg triamcinolone acetonide in the right eye, detected two lines improvement in the BCVA, whereas no change was observed in the BCVA in the non-injected eye.9 In another study, also triamcinolone acetonide was found to be effective in the treatment of IPT.10 In our case, intravitreal TA resulted in decrease in the macular edema and also increased significantly the visual acuity.

Green et al. in their histopathologic study showed that in type 2 IPT, constriction in the capillary vessels and cellular proliferation of basal membrane may cause increase in the thickness of the retinal capillary vessel walls. Because of this structural disorder, the exchange of oxygen and substrates between capillary network and sensorial retina is impaired, so hypoxia develops and as a response to this hypoxia, VEGF is released from the retinal cells.11 Type 2 IPT is a chronic process, therefore, VEGF has a long-term effect on the pathogenesis of type 2 IPT. IVB abolishes the effects of VEGF by inhibiting all isomers of VEGF. Charbel et al.3 have shown that inhibition of VEGF by IVB is associated with a decrease in retinal thickness and a reduction in angiographic leakage in type 2 IPT in short term. In our case, we detected a decrease in the vascular leakage on FA in the eye injected with a single dose of IVB. Consistent with this finding, BCVA also increased.

OCT is a noninvasive imaging technology that provides cross-sectional images of the retina. OCT has added to the understanding of morphologic alterations in IPT. In a recent study, OCT showed some characteristic findings for all stages of type 2A. Those included the presence of highly reflective dots in the inner retina corresponding with vessels on FA, presence of hyporeflective intraretinal spaces within and under the retina, blunting of the foveal pit, and presence of an area of outer and inner retina with similar reflectivity.12 Moreover, Gupta et al.13 suggested that hyporeflective spaces seen on OCT may represent intraretinal cystic spaces secondary to atrophy of the retinal receptors and other retinal cells, most likely Muller cells. It is possible that the cystic spaces are not visualized with FA because they are filled with a lightly staining fibrillar material on the inner plexiform layer, the outer nuclear layer, and the outer plexiform layer as reported in light and electron microscopy by Green et al.14 In the presented case, the OCT images may not show the characteristic findings of IPT because of the low resolution of OCT. The OCT used in the above-cited references was spectral-domain OCT, so this issue may explain the relatively normal anatomy of the macula detected on OCT in the presented case.

In the literature, it is well known that triamcinolone acetonide or bevacizumab given intravitreally can pass into the systemic circulation.15 It is possible that the dose of the drugs that pass in systemic circulation can also affect the pathologies in the non-injected eye. In this case, the effect of the drugs on the telangiectasia in both eyes can be explained also by this mechanism.

In conclusion, we think that intravitreal injection of triamcinolone acetonide and bevacizumab are optional modalities in the treatment of type 2 IPT. The efficacy and duration of action of triamcinolone acetonide and bevacizumab were similar in our case. Besides, these findings warrant further studies with larger number of patients and long-term follow-up.