Introduction
Macular telangiectasia type 2 (MacTel2) is a progressive neurogliovascular macular dystrophy starting in the fifth decade of life and evolving progressively toward macular atrophy.1
When the disease becomes symptomatic, some capillary changes are already present and are characterized by “occult” telangiectasia, mainly on the temporal side of the macula, and often, but not always, associated with a slightly dilated venule originating at right angle from the temporal side of the macula.
Telangiectasia is associated with structural retinal changes such as loss of macular pigment, whitening of the inner retina, crystal deposition in the optic nerve fiber layer, cystic formation in the inner part of the fovea, and outer cavitation. Lastly in some advanced stages of the disease, subretinal new vessels may proliferate from the deep capillary plexus (DCP) and result in bleeding or fibrosis beneath the retina.1
MacTel2 is well imaged by conventional multimodal imaging.2 Fundus autofluorescence (FAF) shows early changes in macular pigment density,3 blue reflectance photograph shows the whitening of the inner retina as a temporal crescent or an oval area occupying the whole macula,4 fluorescein angiography (FA) shows a mild leakage and staining of the retinal tissue at the telangiectasia but no filling of the cystic macular spaces, and structural optical coherence tomography (OCT) shows the inner macular cysts and outer cavitations. En face OCT also shows the areas of ellipsoid zone (EZ) breakdown in the vicinity of the foveal center, as well as microcavitations5 in the inner nuclear layer and ganglion cell layer, extending through the whole area of the “MacTel” zone. Finally, adaptive optics (AO) has shown the loss of photoreceptor cells in the areas of EZ breakdown, but with the persistence of some cone elements.6,7
OCT angiography (OCTA) provides new details of the telangiectasia, which gave their name to the disease, although they are only part of the disease spectrum.
Before the era of OCT and modern multimodal imaging, Mactel2 (initially called idiopathic juxtafoveal telangiectasia8) were classified into five stages, which do not fit well with the anomalies observed nowadays. We will therefore use the terms “early,” “intermediate,” “advanced,” and “atrophic” to describe the progressive increase in capillary anomaly severity, although another system of grading has been proposed recently based on OCTA.9
11.2 Early Stage with Isolated Telangiectasia
At an early stage, telangiectasias are barely visible on fundus examination, and only a minimal leakage is seen on FA. OCTA shows a mild dilation of both the superficial capillary plexus (SCP) and the DCP on the temporal side of the fovea. The capillary density ranges within normal values in both the SCP and the DCP. A venule draining the temporal part of the fovea may be slightly dilated ( ▶ Fig. 11.1).
Fig. 11.1 Early stage of macular telangiectasia type 2 (MacTel2) with minimal macular capillary dilation. (a) The color photo shows no significant changes in the macula. (b) The blue reflectance image shows a temporomacular crescent of inner retinal whitening characteristic of the disease. (c) On fluorescein angiography, a mild hyperfluorescence is visible on the temporal side of the fovea (arrows) without clear visibility of telangiectasia. (d) Optical coherence tomography (OCT) angiogram segmented at the superficial capillary plexus (SCP) showing a very mild dilation of the superficial capillaries and a slightly tortuous venule (arrow). (e) Corresponding OCT B-scan showing only a small inner cystic cavity on the temporal side of the fovea. (f) Deep capillary plexus (DCP) with small dilated capillaries temporal to the fovea (arrows). (g) Corresponding OCT B-scan on which the vascular flow (red points) does not appear abnormal. (h) En face (nonflow) image showing the parafoveal inner cysts (arrow) with its correspondence on the (i) structural B-scan. Capillary density (j) at the SCP and (k) at the DCP ranging within normal values.
In other cases, a capillary dilation and an irregular pattern are more visible and more extended, especially in the DCP ( ▶ Fig. 11.2), and are associated with some capillary ectasia and a dilated draining venule. On the en face image, large cystic cavities are present on the temporal part of the foveal center, as well as other microcysts in the ganglion cell layer and inner nuclear layer, which correspond to small lacunae in the SCP and DCP. There is globally some degree of capillary rarefaction, mainly in the DCP, and a decrease in capillary density.3,9,10
Fig. 11.2 Early stage of macular telangiectasia type 2 (MacTel2) with macular capillary and venular dilation. (a) Optical coherence tomography (OCT) angiogram segmented at the superficial capillary plexus (SCP) showing some degree of dilation of the superficial capillaries and an enlargement of the intercapillary space. A temporal venule (V) is slightly dilated (arrow) and corresponds on (b) the OCT B-scan to an increase in vascular flow. Note also the small cystic cavity in the temporal side of the fovea. (c) Deep capillary plexus (DCP) with more pronounced dilation of the deep capillaries and dilation of the deep part of the dilated venule (V), which corresponds on (d) the OCT B-scan to an increase in vascular flow (arrow). (e,f) En face (nonflow) image segmented at the SCP and corresponding OCT B-scan showing several microcysts (one of them marked by an arrow) located at various levels of the inner retina. Note also the stellate pattern of the inner foveal cysts in the temporal part of the fovea. (g,h) On the OCT angiogram of the DCP and on the corresponding OCT B-scan, these microcysts correspond to small capillary voids (arrows). (i) Capillary density at the SCP and (j) at the DCP are smaller than normal.
11.3 Intermediate Stage with Outer Intraretinal New Vessels
At an intermediate stage, a dilated venule emerges on the temporal side of the macula and drains the cluster of coarse capillaries in the SCP and DCP, usually adjacent to inner foveal cystic spaces ( ▶ Fig. 11.3). The foveal avascular zone (FAZ) is dragged temporally,5 and the capillaries of the SCP are rarefied and dilated. These capillary anomalies are more pronounced in the DCP where they extend to the whole macular area. Telangiectasia are better seen on OCTA than on FA.9,11 Moreover, OCTA shows a subjacent layer of capillaries invading the outer nuclear layer (ONL) in front of the area of EZ loss temporal to the fovea.
Fig. 11.3 Intermediate stage of macular telangiectasia type 2 (MacTel2) with outer intraretinal new vessels. (a) Optical coherence tomography (OCT) angiogram of the superficial capillary plexus (SCP) showing a dilated venule originating at right angle from the temporal part of the fovea (arrow). The capillaries are dilated and rarefied with increased intervascular spaces. The foveal avascular zone (FAZ) is slightly dragged temporally. (b) Corresponding OCT B-scan passing through the termination of the right angle venule showing an increased vascular flow at this level (arrow). (c,d) Coarse capillaries in the deep capillary plexus (DCP) and corresponding OCT B-scan. (e,f) Fluorescein angiography showing the dilated capillaries less distinctly than OCT angiography, and corresponding structural OCT B-scan. (g,h) Segmentation at the outer retina (large arrow) showing an abnormal capillary network in yellow (g) corresponding to the vascular flow just above the retinal pigment epithelium (ellipse) on (h) the OCT B-scan. (i) En face OCT (nonflow) segmented at the DCP. Note the presence of numerous microcysts (light arrows on some of them), and the visibility of some dilated coarse capillaries (large arrow). (j) Corresponding structural OCT B-scan showing the collapse of the outer nuclear layer on the retinal pigment epithelium (large arrow). (k) En face OCT segmented at the ellipsoid zone (EZ); the black area corresponds to the EZ loss. (l) Corresponding OCT B-scan with a double red line showing the segmentation at the EZ.
A dilated venule and FAZ distortion may be associated with intraretinal pigment proliferation ( ▶ Fig. 11.4). These pigmentary plaques are well visible on color photos. On structural OCT, they appear as a hyper-reflective structure occupying almost the whole retinal thickness on the temporal side of the FAZ, in an area of EZ loss. On the OCT B-scan, their flow is relatively high and they are located at the convergence of telangiectatic capillaries into the right angle venule.12
Fig. 11.4 Intermediate stage of macular telangiectasia type 2 (MacTel2) with outer intraretinal new vessels and intraretinal pigment proliferation. (a) Color photo showing a pigmented plaque temporal to the fovea (arrow) better seen on (b) the red-free filter image where it surrounds the extremity of a dilated venule (arrow). (c) Fluorescein angiography shows the capillary dilation on the temporal side of the fovea. (d) Superficial capillary plexus (SCP) with telangiectasia drained by a dilated venule (arrow). The foveal avascular zone (FAZ) is enlarged and dragged toward the pigmented plaque and dilated venule. (e) Corresponding optical coherence tomography (OCT) B-scan showing a high flow below the emergence of the dilated venule in the deeper part of the retina (arrow). (f) Deep capillary plexus (DCP) showing coarse capillaries converging toward the origin of the dilated venule, temporal to the fovea (arrow). (g) The structural OCT B-scan shows the increased focal reflectivity of the retinal tissue (arrow) underlying the extremity of the dilated venule and containing the vascular flow as seen in (e). (h) OCT angiogram segmented at the posterior edge of the inner nuclear layer showing the deepest capillaries of the DCP (in purple) behind which an additional network is visible (in yellow). (i) Corresponding OCT B-scan at a level different from that of (e) showing the flow (ellipse) just above the retinal pigment epithelium (RPE). (j) OCT angiogram segmented above the RPE showing the network of outer intraretinal new vessels corresponding to the flow (red dots) seen in (k) above the RPE. (l) En face OCT segmented at the ellipsoid zone (EZ) showing a black area corresponding to the irregular patchy loss of EZ. The green line corresponds to the EZ loss seen on the structural OCT B-scan in (m). (n) Superimposition of the outer intraretinal neovascular network on the en face image segmented at the EZ, showing that the intraretinal new vessels have proliferated in front of the area of EZ loss. (o) Corresponding abnormal flow on the OCT-A B-scan.
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