Idiopathic juxtafoveolar retinal telangiectasis (IJRT) is classified into three groups.1 2 Group 2A IJRT is the most common subtype characterised by bilateral, idiopathic, acquired parafoveolar telangiectasis, right-angle venule (RaV) and sometimes subretinal neovascularisation.1^–3 Gass and associates1 2 classified group 2A IJRT into five stages: (1) late-phase staining on fluorescein angiography (FA) only; (2) mild capillary telangiectasis on FA; (3) biomicroscopic dilated capillary changes and a RaV; (4) retinal pigment epithelial hyperplasia in the retina; and (5) neovascularisation.

Some studies using the optical coherence tomography (OCT) have reported loss of photoreceptor layer and cystic changes in group 2A IJRT on a Stratus OCT, OCT-Ophthalmoscope, and ultra high-resolution OCT.4^–8 However, the exact mechanism of these changes is not fully understood. Spectral domain OCT (SD-OCT) or Fourier domain OCT, a recently developed high-speed, high-resolution technology, provides serial images of the retinal details constructed into three-dimensional images using a volume rendering method.9 10

Although visual acuity loss in group 2A IJRT is usually minimal until exudation or neovascularisation occurs, central visual dysfunction is sometimes a main dissatisfaction because of degeneration or atrophy of the neurosensory retina.4 Microperimetry is the device for macular sensitivity or functional macular mapping, and useful to detect small scotoma in group 2A IJRT. Charbel Issa et al7 studied the correlation between the retinal thickness on stratus OCT and the retinal function using microperimetry in patients with group 2A IJRT, and concluded that qualitative assessment of OCT images may be more important in understanding functional defects than assessment of retinal thickness.

In the current report, we observed early morphological changes using SD-OCT, and also observed central macular sensitivity using microperimetry in group 2A IJRT.

METHODS

Six eyes of three patients with group 2A IJRT were studied. The mean age of three patients was 64 years. The clinical examination for diagnosis and staging of group 2A IJRT included indirect ophthalmoscopy, slit-lamp biomicroscopy with a contact lens, and digital FA (TRC-50IX/IMAGEnet H1024 system, Topcon, Tokyo). Informed consent was obtained from all patients. For this retrospective study, institutional review board/ethnic committee approval was not required.

Five eyes had temporal retinal capillary dilatation on early-phase FA and minimal leakage in the late phase. One eye had the unusual course of macular vessels that did not respect the horizontal raphe (case 2). One eye had no capillary abnormalities on biomicroscopy, but late-phase leakage on FA. In three eyes with dilated capillaries, RaV was observed. According to Gass classification,1 2 one eye with stage 1 disease had minimal leakage on FA, two eyes with stage 2 disease had minimally dilated capillaries on biomicroscopy and FA, and three eyes with stage 3 disease had dilated capillaries and an RaV. All eyes with early stage of group 2A IJRT (ie, stage 1 to 3) were studied in this report.

All patients were examined by SD-OCT (3D-OCT, Topcon, Tokyo) with a resolution to less than 5 μm. Volume rendering of 3D-OCT data was performed using image-processing software (Amira 4.1, Mercury Computer System, Chelmsford, MA). OCT findings using time domain OCT of all patients were previously reported.4

All patients were examined using microperimetry (MP-1, Nidek Technologies, Padua, Italy) contained an automatic eye tracking system.11 Goldmann II stimuli and a 4-2 staircase strategy were used, and the testing grid pattern of 45 points covering 8° diameter for detecting small scotoma was applied. Because all patients had felt only central visual dysfunction without visual acuity loss, we selected the Goldmann II stimuli in order to detect the relative scotoma. The learning effect is not compensated by this procedure; however, this is not of interest in this study, since no microperimetric follow-up data are shown.

RESULTS

The clinical characteristics of cases 1–3 are summarised in table 1. On 3D-OCT, breaks in the highly reflective line, that is, the presumed boundary between the photoreceptor inner and outer segments (IS/OS), were seen at the temporal to the fovea within the area of fluorescein leakage in all six eyes (figs 1A, 2A, B, 3A, B). The highly reflective tissue was observed in the outer retinal layer in five eyes except for one eye with stage 1. Cystic changes in the inner retinal layer without a corresponding area of minimal leakage on FA were seen in the five eyes on 3D-OCT. In three eyes with an RaV (stage 3), the outer retinal layer structures disappeared at the temporal to the fovea corresponding to the area of RaV and were replaced by the highly reflective tissue. The inner retinal layer was drawn into the highly reflective tissue in the serial images of 3D-OCT (fig 3C).

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Figure 1 Case 1: a 67-year-old woman, left eye, stage 1. (A) Late-phase fluorescein angiography of the left eye shows minimal leakage at the temporal to the fovea. (B) Sectioned volume of a 3D image through the centre of the fovea shows the break in the boundary between the photoreceptor inner and outer segments (IS/OS) at the temporal to the fovea (between arrowheads).

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Figure 2 Case 2: a 57-year-old woman, left eye, stage 2. (A) Early phase and (B) late-phase fluorescein angiography show minimally dilated capillaries at the temporal to the fovea. There is the unusual course of macular vessels that did not respect the horizontal raphe without the leakage and cystic change at the temporal area. (C) Sectioned volume of a 3D image through the centre of the fovea showing disappearance of the boundary between the photoreceptor inner and outer segments (IS/OS) at the temporal to the fovea (between arrowheads). Highly reflective tissue is under the fovea in the outer retinal layer (arrow). (D) Result of microperimetry used by the grid pattern with 45 points covering 8° diameter showing the central scotoma (orange and yellow squares) at the temporal to the fovea corresponding to the area of IS/OS break. Colour squares correspond with the dB sensitivity scale on the bottom right.

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Figure 3 Case 3: a 67-year-old man, right eye, stage 3. (A) Red-free fundus photograph and (B) late-phase fluorescein angiography showing a right-angle venule at the temporal to the fovea and minimal leakage (arrows). (C) Sectioned volume of a 3D image through the centre of the fovea showing that the structure of the outer retinal layer has disappeared (between arrowheads) and replaced by highly reflective tissue at the corresponding area of a right-angle venule. The inner retinal layer is dragged into the highly reflective tissue. (D) Result of microperimetry used by the grid pattern with 45 points covering 8° diameter showing the central scotoma (red squares) at the temporal to the fovea corresponding to the area of a right-angle venule. Colour squares correspond with the dB sensitivity scale on the bottom right.

MP-1 showed the reduction in the retinal sensitivity thresholds at the temporal to the fovea in five eyes except for one eye with stage 1. The location of low sensitivity in MP-1 was found at the area of breaks of IS/OS in eyes with stage 2 (fig 2D) and the area of RaV corresponding to the disappearance of outer retinal layer in eyes with stage 3 (fig 3D).

DISCUSSION

The breaks in the IS/OS were observed in stages 1 and 2 (figs 1, 2), and the retinal outer layer was ultimately replaced by the highly reflective tissue in stage 3 (fig 3) on 3D-OCT. The highly reflective tissue in the outer retinal layer and cystic changes in the inner retinal layer were seen in five eyes except for one eye with stage 1. The unusual course of macular vessels beyond the horizontal raphe in the left eye of case 2 (fig 2) could not relate with the capillary abnormalities and cystic change on FA. MP-1 showed the small scotoma at the temporal to the fovea in five eyes except for one eye with stage 1. The location of scotoma in MP-1 was identical in area with breaks of IS/OS in eyes with stage 2 and RaV in eyes with stage 3, which was not corresponding to the area with cystic change in the inner retinal layer.

We previously reported that degeneration or atrophy of the neurosensory retina, including the photoreceptor layers, might be one of the major causes of group 2A IJRT on the OCT-Ophthalmoscope.4 3D-OCT has enabled better visualisation of the early progressive course than the OCT-Ophthalmoscope. Central visual disturbance without visual acuity loss is a main symptom in the early stage of group 2A IJRT. Charbel Issa and associates12 reported central visual function using microperimetry and correlated functional deficits with findings on ophthalmoscopy and OCT imaging. We evaluated macular sensitivity using MP-1 and studied detailed morphological changes using 3D-OCT of group 2A IJRT at the same time.

On 3D-OCT, the highly reflective tissue was already observed in stage 2, and this tissue was dragged into the inner layer in the stage 3. No articles have mentioned the highly reflective tissues in early stage of group 2A IJRT on OCT. Both high speed and high resolution are needed to detect highly reflective tissues. Koizumi and associates13 reported two cases of full-thickness macular holes with good visual acuity in group 2A IJRT, and concluded that the formation of macular holes in IJRT might be induced by abnormal Müller cells, particularly Müller cell cones that are elemental basement structures of foveola. Gass and associates1 2 described that “telangiectatic” changes in capillaries, associated with decreased metabolic exchange, damage the retinal inner nuclear layer that included the Müller cells in group 2A IJRT. Although the cause of capillary alterations is unclear, the disorder of Müller cells may occur in the early stage of group 2A IJRT. The morphological changes in the outer layer may be caused by abnormal Müller cells, and the highly reflective tissue and its dragging into the inner retinal layer may manifest as visible alterations of Müller cells on 3D-OCT. It is also possible using 3D-OCT to determine that the inner retinal layers may move outwards only due to atrophy within the outer retinal layers.

Müller cell alterations may induce drawing of the capillaries and vein into the inner retinal layer. The aggregated formation observed as the highly reflective tissue on 3D-OCT may be a precursor lesion to subretinal neovascularisation in the advanced stages of group 2A IJRT. The resulting neovascularisation may be associated with production of vascular endothelial growth factor from abnormal Müller cells.

On the other hand, MP-1 showed a small scotoma regardless of visual acuity at the temporal to the fovea in the area with IS/OS breaks or the area of RaVs corresponding to the disappearance of outer retinal layer in five eyes. These may indicate the disorder of the photoreceptor cell itself occurring in areas of IS/OS breaks. 3D-OCT compared with conventional stratus OCT12 may enable detailed morphological changes to be observed in the scotoma area on MP-1 in group 2A IJRT. Gass and associates1 2 also reported abnormal Müller cells due to nutritional deprivation with alterations of capillaries flow leading to degeneration and atrophy of these cells and the connecting photoreceptor cells. Because the breaks in IS/OS were observed even in stage 1 without capillary dilatation, degeneration or atrophy of the photoreceptor layers may be the primary alteration of group 2A IJRT, and then proliferation of Müller cells may occur to repair the photoreceptor layers. Although disorder in group 2A IJRT originates from Müller cells or photoreceptor cells, both of them already seem to show the morphological change and functional abnormality in the early stages from the results of 3D-OCT and MP-1.

We observed early morphological alterations in group 2A IJRT in 3D-OCT serial images. The degeneration or proliferation in the outer retinal layer may have already occurred in the early stages, and the inner retina may have been dragged later, as determined by visualisation of Müller cell abnormality on 3D-OCT. At the same time, the disorder of photoreceptors occurs in the area with an IS/OS break, from the results of MP-1. Although the numbers of patients were small, detailed observations of these abnormalities provide an understanding of the morphological and functional features of group 2A IJRT.