Case Report The Use of Swept Source Oct Angio in Diagnosis and Staging of Type 2 Macular Telangictasia (Mactel 2)

Diagnosis and staging of macular telangiectasia type 2 (MacTel2) using Swept Source optical coherence tomography angiography


Introduction
Macular telangiectasia type 2 has also been termed idiopathic perifoveal telangiectasia or idiopathic juxtafovealtelangiectasis type 2 [1][2][3]. It is now referred to as MacTel type 2, and it is a bilateral perifovealvasculopathy which originates in the deep retinal capillary plexus in the temporal juxtafoveal region. As it progresses, it involves the superficial retinal capillary plexus, and continues to progress anteriorly, posteriorly, and circumferentially. This is called the non-proliferative stage of the disease [5][6][7][8][9]. Mactel type 2 becomes proliferative when the vasogenic process extends under the retina, forming detachment and a retinal-retinal anastomosis. This form of the disease may eventually lead to disc form scarring.
In the early stages of the disease, Fluoresce in Angiography (FA) imaging shows abnormal hyper fluorescence and leakage from the temporal, juxtafoveal capillary plexus, 7 as the disease progresses, the hyper fluorescence and leakage spreads circumferentially around the fovea. While FA provides a definitive diagnosis of MacTel2, it also involves the intravenous injection of a dye that can result in adverse effects such as nausea or vomiting, and rarely fluoresce in can elicit an anaphylactic response [11,12]. Auto Fluorescence (AF) imaging is also useful in diagnosing MacTel2 [13], Due to the depletion of luteal pigment in the temporal juxtafoveal retina, a relative increase in AF is observed in this region [14][15][16]. As the disease progresses, luteal pigment is lost circumferentially around the fovea and an increase in the relative hyper fluorescence is observed. In the later stages of the disease, atrophy of the RPE is observed, resulting in decreased AF within the central macula.
Optical Coherence Tomography (OCT), a non invasive imaging modality, has revealed structural abnormalities in the inner retina such as retinal cavitations with draping of the internal limiting membrane and abnormalities in the outer retina such as disruption of the photoreceptor inner segment/outer segment/ellipsoid (IS/OS/E) region that were not previously appreciated by FA or AF imaging [18][19][20][21][22][23][24][25]. OCT imaging has improved the early detection of MacTel2 by identifying these early subtle changes in retinal anatomy, and OCT has proven to be useful for following these alterations in macular anatomy as the disease progresses to fovea atrophy, the formation of intraretinal pigment plaques, and sub retinal neovascularization.With the development of Spectral Domain-OCT (SD OCT) instruments with increased scanning speeds and high speedswept source OCT (SS OCT) instruments, OCT Micro Angiography (OMAG) imaging has emerged as a noninvasive strategy to visualize the retina and choroidal microvasculature without the use of an exogenous intravenous dye injection [26][27][28][29][30][31][32][33][34][35][36][37][38][39][40], OMAG is a dynamic strategy capable of providing a three dimensional reconstruction of the per fused microvasculature within the retina and choroid and identifying distinct characteristics of the capillary networks located within different layers of the retina and choroid (see "Swept Source OCT Angiography of the Retinal Vasculature Using Intensity Differentiation based Optical Micro angiography.

Aim & Objectives
To evaluate the central macular micro vascular network in patients with macular telangiectasia type 2 (MacTel2) using Swept Source optical coherence tomography Angiography.

Patient & Method
We retrospectively review a 60 Y old patient with bilateral-MacTel2 evaluated using a Swept Source OCT (SS OCT). The patient underwent a comprehensive ocular examination and imaging tests as part of the evaluation of her condition. The imaging tests included color fund us imaging (Topcon, Tokyo, Japan), digital fund us AF imaging, FA& Swept Source OCT with OCT Angio (TRITON TOPCON OCT).
The patient had no any other retinal pathology such as diabetic retinopathy or pathologic myopia and not previously treated with Photo Dynamic Therapy (PDT), thermal laser, intravitreal in-jections, or any retinal surgery. Information about previous medical conditions and ocular treatments was obtained by reviewing the medical charts. the retina was segmented into three distinct physiological layers: an inner retinal layer from the Ganglion Cell Layer, To The Inner Plexiform Layer (GCL + IPL), a middle retinal layer from the Inner Nuclear Layer To The Outer Plexiform Layer (INL + OPL), and an outer retinal layer from Outer Nuclear Layer to the External Limiting Membrane (ONL + ELM layer). The microvasculature from the superficial capillary plexus in the inner retina is colored red, the microvasculature from the deep capillary plexus is colored green, and any micro vascular structures with flow in the outer retina are colored blue.

Results
(SS-OCT A) detected abnormal microvasculature in all Mac-Tel2 eyes, predominantly in the middle retinal layer. These vessels correlated well with the FA alterations. The abnormal temporal, juxtafoveal microvasculature in MacTel2 became apparent as the disease progressed and in later stages tended to extend circumferentially, with anastomotic vessels temporally.
In our Case, the Right Eye was in Early, No proliferative MacTel2, Best corrected Visual Acuity (BCVA) in her left eye was 20/30. The horizontal Bscan with the retinal flow in different layers represented by colors shows the dilated vessels in the deep retinal capillary plexus found in the middle retinal layer, most pronounced in the region temporal to the fovea as observed in green ( Figure 1A & B).      Details the presence of abnormal microvasculature (green and blue corresponding to an area with retinal vascular anastomoses. Disruption of the microvasculature extends into the outer retina where the IS/OS/E is disrupted. Micro vascular abnormalities, such as a distorted juxtafoveal capillary plexus with prominent anastomoses, FA imaging demonstrates hyper fluorescence in the temporal juxtafoveal region in the earliest stage associated with late leakage (Figure 5).

Conclusion
We used the SS-OCT Angio technique to investigate eyes with MacTel2 using a TRITON SS OCT. To extract the blood flow information and visualize the microvasculature of the central macula, the central macular microvasculature was visualized well than with FA imaging. In addition, the better visualization of the juxtafoveal microvasculature with SS-OCT Angio may also be due, in part, to the absence of leakage on OCT Angio imaging, and it is this leakage that could obscure the normal vasculature seen on routine FA imaging. By using this ability to extract and visualize these retinal layers in MacTel2 and other diseases, SS-OCT Angio imaging may help facilitate the early diagnosis of disease and provide a better understanding of disease progression and the efficacy of treatments and to differentiate MacTel2 from other diseases affecting the retinal microvasculature associated with fluorescein angiographic leakage, such as neovascularage related macular degeneration, diabetic macular edema, vein occlusions, and cystoids macular edema from differing conditions.
In conclusion, OMAG is a noninvasive imaging strategy that holds great promise for the evaluation of eyes with MacTel2 and other diseases affecting the retinal microvasculature associated with fluorescein angiographic leakage, such as neovascularage related macular degeneration, diabetic macular edema, vein occlusions, and cystoids macular edema from differing conditions. In addition, OMAG should be useful in investigating the path physiology of angiographicallysilent cystoids macular edema, such as the micro vascular changes associated withthetaxane class of medications (paclitaxel and docetaxel), vitreomacular traction, epiretinal membranes, niacin maculopathy, juvenile retinoschisis, retinitis pimentos, and Goldman Favre disease. However, different patterns of retinal segmentation may be needed to highlight the underlying microangiopathy using OMAG, and all the different segmentations are derived from one three-dimensional data set, which takes about 4.5 seconds to acquire and has none of the potential adverse events associated with FA. This study demonstrated the ability of OMAG to image the perifoveal microvasculature in eyes with different stages of MacTel2, but further studies are needed to quantitative vascular caliber, density, and blood flow in the central macula and identify whether changes in these parameters predict disease progression or response to future therapeutic interventions. 11/27/2016 Swept Source OCT Angiography of Macular Telangiectasia Type 2http://www.healio.com/ophthalmology/journals/osli/2014 9 45 5/%7B849feaaa 8a02 4232-92ec 8b4fd894db7d%7D/swept source oct angiography of m… 34/37 [CrossRef]