Downloaded from http://bjo.bmj.com/ on November 15, 2016 - Published by group.bmj.com Clinical science Characteristics and quantification of vascular changes in macular telangiectasia type 2 on optical coherence tomography angiography Lavanya Chidambara,1 Santosh G K Gadde,1 Naresh Kumar Yadav,1 Chaitra Jayadev,1 Devanshi Bhanushali,1 Abhishek M Appaji,2 Mukunda Akkali,1 Aruj Khurana,1 Rohit Shetty1

1Narayana Nethralaya Eye ABSTRACT MacTel type 2 (MacTel 2) is a bilateral disease Hospital, Bangalore, India Background Macular telangiectasia type 2 (MacTel 2) characterised by changes in the capillary network 2BMS College of Engineering, Bangalore, India is a bilateral idiopathic, rare neurodegenerative disease and neurosensory . Slit lamp biomicroscopy with alterations in the macular capillary network leading reveals reduced retinal transparency, crystalline Corresponding to to vision loss and is the most common of three subtypes. deposits, ectatic capillaries and blunted venules.4 Dr Santosh G K Gadde, Optical coherence tomography angiography (OCTA) is a Complications of this disorder include proliferation Department of Vitreo-, non-invasive imaging modality which helps understand of pigment plaques, photoreceptor loss, foveal Narayana Nethralaya, #121, Chord Road, 1st ‘R’ Block, the complex pathological changes, and images the blood atrophy and retinal neovascularisation that may 5 Rajaji Nagar, Bangalore, vessels across different layers based on their flow result in visual loss. Karnataka 560010, India; characteristics. Stereoscopic colour and red-free fundus photog- [email protected] Methods A cross-sectional study was conducted on raphy and fundus fluorescein angiography (FA) Received 7 October 2015 56 eyes of Asian Indian eyes of 28 consecutive patients have been previously used to describe the disease. Revised 23 December 2015 with MacTel 2 studied during a 3-month period in a Optical coherence tomography (OCT) provides Accepted 30 December 2015 tertiary eye care hospital of South India. Clinically useful visualisation of the retinal and choroidal Published Online First diagnosed cases of MacTel 2 underwent fundus changes in patients with MacTel 2. The currently 28 January 2016 photography, spectral domain OCT and OCTA. described spectral domain OCT signs (SD-OCT) of was performed only when MacTel 2 include hyporeflective spaces in the inner clinically indicated. Mean capillary density was calculated and the outer retina (retinal cysts), plaques and using a MATLAB-based automated software. The images breaks in the ellipsoid zone with progressive outer were thresholded and binarised to derive the mean retinal atrophy in which the retinal layers interior value. to the outer nuclear layer seemingly ‘collapse’ Results The mean age at presentation was 60±5.2, through these breaks towards the retinal pigment with a female preponderance of 71.42%. Vascular epithelium (RPE).67Progression of the disease is network on OCTA shows an increase in the intervascular characterised by shrinkage of the outer retinal spaces with progressive capillary rarefaction and layers and reduction in the central foveal thickness abnormal capillary anastomosis. The outer retina and (CFT).8 En face OCT also enables visualisation of choroid were involved during the later stages and the pigment plaques and new vessels in the various showed a prominent vascular network. The mean retinal layers along with the extent of associated capillary density of the superficial and deep layers was exudation.59 39.99% and 39.03% as against 45.18% and 44.21% FA is the gold standard to confirm the diagnosis in the controls, respectively. There was a statistically of MacTel 2 showing telangiectatic capillaries pre- significant difference between the two groups (p<0.01). dominantly temporal to the foveola10 in the early There is a positive and statistically significant correlation phase and a diffuse hyperfluorescence in the late between the superficial and deep layers. phase. The late hyperfluorescence can be seen even Conclusion OCTA helps understand the and in the absence of telangiectatic alterations. Gass disease progression better in MacTel 2. and Oyakawa1 on studying stereoscopic angio- graphic images have suggested that vascular altera- tions mainly affect the deeper capillary plexus and that the late diffuse fluorescence on FA appears to INTRODUCTION originate from the outer retina. The finer morpho- Macular telangiectasia (MacTel) is characterised by logical changes in the vascular network are abnormalities of the capillaries around the fovea. obscured by the diffuse hyperfluorescence and FA The condition can be a result of a retinal vascular fails to provide details about the deeper retinal disease or systemic diseases such as or layers and finer pathological changes. Besides, FA is , but is most often idiopathic. MacTel an invasive imaging modality with documented was formerly called idiopathic juxtafoveolar retinal side effects and repeating the test at every visit may telangiectasis and was classified into three not be feasible. 12 To cite: Chidambara L, groups. Recent advances in imaging have OCT angiography (OCTA) is a new imaging Gadde SGK, Yadav NK, allowed better characterisation of the disease to modality that allows high-resolution imaging of the et al. Br J Ophthalmol define it into two distinct forms, type 1 and type 2 retinal morphology, especially of individual vascu- – 2016;100:1482 1488. MacTel.3 lar layers, without the use of an injectable dye. It

1482 Chidambara L, et al. Br J Ophthalmol 2016;100:1482–1488. doi:10.1136/bjophthalmol-2015-307941 Downloaded from http://bjo.bmj.com/ on November 15, 2016 - Published by group.bmj.com Clinical science

has an A-scan rate of 70 000 scans/s, using a light source centred on 840 nm and a bandwidth of 45 nm. The tissue reso- lution is 5 μm axially with a 22 μm beam width. Each B-scan contains 512 A scans.11 RTVue XR 100 (Avanti, Fremont, California, USA) uses the split spectrum amplitude decorrelation algorithm to acquire information on the flow in the retinal and choroidal vasculature.12

Objective The aim of the study was to describe the OCTA features of the different stages of MacTel 2. The capillary density of the super- ficial and deep layers of retina were studied and compared with controls.

PATIENTS AND METHODS Study design It is a cross-sectional, observational study. OCTA was performed in 56 Asian Indian eyes of 28 consecu- tive patients with clinically confirmed MacTel 2 for a period of 3 months (February–April 2015) in a tertiary eye care hospital in South India. Ten eyes of five age-matched controls with a normal ophthalmic examination were included in the study. The study met the approval of the Institute Research Board and the Institute Ethics Committee and informed consents were obtained from all enrolled subjects. The study adhered to the Figure 1 Offset and default segmentation of normal retina. ILM, tenets of the Declaration of Helsinki. internal limiting membrane; IPL, inner plexiform layer; RPE, retinal All patients underwent a complete ophthalmic examination pigment epithelium. along with , OCT (Heidelberg engineering, Spectralis (V.6.0) GmBH) and OCTA (Optovue RTVue XR 100 fi Avanti, Fremont, California, USA). FA (Heidelberg engineering, The nal output gave a measure of the total area of study, capil- fi Spectralis (V.6.0), GmBH) was performed only in advanced lary area and percentage of capillary density in pixels ( gure 2). cases when clinically indicated. The Gass and Blodi classifica- tion4 was used for classifying subjects into the five clinical Statistical analysis stages. For statistical analysis, IBM SPSS Statistics 22 was used. Since all A single technician acquired a mydriatic OCTA with two con- variables studied exhibited a normal distribution, parametric secutive scans of 3 by 3 mm centred on the macula with an tests were conducted. Post-hoc tests were applied wherever internal fixating target. The OCTA images were independently necessary. Pearson’s correlation coefficients were calculated to graded and assessed by two clinicians. Segmentation of the investigate bivariate relationships and partial correlation coeffi- superficial, deep, outer retina and choroidal levels was done cients were calculated when controlling for confounding vari- with a default standard offset with segmentation layers based at ables. We used the 5% level of significance throughout our internal limiting membrane, inner plexiform layer and RPE analysis. Independent samples t-test was performed to compare (figure 1). In advanced cases of MacTel 2 where the retinal the capillary density between patients with MacTel 2 and con- architecture was altered with gross foveal thinning and extensive trols. One-way analysis of variance was performed to evaluate cystic spaces, the offset was manually adjusted to acquire the the difference in the capillary density of the different stages of right segmentation of layers before analysis. the disease. The outer retina showed speckled pattern occasionally sec- ondary to an artefact or noise which was minimised with the RESULTS ‘remove artefacts’ option of the software and by adjusting the The demographic and vision-related data of the 28 subjects offset to the possible limit in case of architectural changes, recruited into the study are summarised in table 1. The age of based on the B scan. Other occasional artefacts included super- the patients in the cohort ranged from 42 to 75 years with a imposed vessel imprints across different plexus. This was over- mean±SD of 60±5.2. come by manual segmentation to some extent. A MATLAB-based, semi-automated software called Ex_GUI OCTA features was designed indigenously for the quantification of capillary The OCTA features of each layer are described. Early changes density in the perifoveal region. A 3 mm diameter circular area begin in the superficial and deep vascular network progressing centred on the fovea was considered and the capillary density of outwards with disease severity. Manual segmentation was circular area was calculated by the automated software. The applied when the CFT was less than 150 μ and in grossly dis- green channel of the RGB image was extracted, as the green torted maculae. channel component has the highest contrast. Image enhance- ment was performed on this extracted image, after the selection/ Superficial layer demarcation of the area of the study. The contrast was increased Stages 1–3(figure 3A–C) had enlargement of the foveal after background subtraction to remove the artefacts. The avascular zone (FAZ), beginning temporally with a progressive Otsu’s thresholding was used to binarise the resultant image. horizontal increase in the FAZ diameter in the later stages.

Chidambara L, et al. Br J Ophthalmol 2016;100:1482–1488. doi:10.1136/bjophthalmol-2015-307941 1483 Downloaded from http://bjo.bmj.com/ on November 15, 2016 - Published by group.bmj.com Clinical science

Figure 2 Pictorial representation of Ex_GUI software.

The perifoveal capillaries showed abnormalities in the network, Stages 4 and 5 (figures 4 and 5A, B) demonstrated a gross the vessel size and their arrangement. There was an increase in decrease in retinal thickness and extensive empty spaces show the intervascular space with progressive capillary rarefaction. prominent larger blood vessels with radiating branches and These changes were accompanied by abnormal anastomoses widespread dark grey empty areas. The right-angled dipping of between the capillary networks of the superficial and deeper the larger blood vessels was better defined with surrounding layers. The finer vascular anastomoses could be appreciated as darker areas corresponding to RPE hyperplasia in atrophic discrete bunches at multiple areas, more in the temporal aspect retinae. of the macula. The abrupt ending of these vessels could be due Three patients of stage 5 showed a choroidal neovascular to a gross decrease in the finer capillary network. The changes membrane (CNVM) with scarring, significant decrease in capil- in larger blood vessels were more pronounced in the later stages laries with prominent larger blood vessels and distorted anatom- with an abrupt ending and posterior dipping which could be ical landmarks. traced into the deeper layers with adjustment of segmentation. Deep layer The deeper layer showed similar changes as in the superficial layer with few pathognomonic alterations. The deeper layer Table 1 Demographic details demonstrated changes earlier than the superficial layer in the Parameters initial stages. The normal close-knit ring of perifoveal capillaries decreased in density, but appeared more pronounced and Age 60±5.2 SD brighter (figure 3B). There was a patchy loss of the network Sex 16 men temporally to begin with and progressive loss of the entire ring 40 women leading to an increase in the FAZ diameter in the later stages. BCVA 0.45±0.23 SD Brush-like branching pattern of smaller vessels secondary to Clinical stages 1–14 (25%) capillary barring was evident (figure 4). The larger blood vessels 2–15 (26.78%) lost the right-angled entry and branching pattern. Prominent 3–14 (25%) larger vessel segments could be appreciated at multiple places 4–10 (17.85%) with blunt ends suggestive of vessel dipping and gross capillary 5–3 (5.3%) rarefaction (figure 5B). CFT (Mean) 194.29±64.24 IS/OS disruption 40 present Outer retina Stage 1 5 The outer retina is a vessel-free dark area with very minimal Stage 2 10 bright speckles in normal individuals. The initial stages remain Stage 3 12 dark if the architecture is grossly maintained. A prominent vas- Stage 4 10 cular network with larger vessels that can be traced back to the Stage 5 3 superficial and deeper networks with a few bright and dark 16 absent areas suggestive of scarring and RPE hyperplasia were seen in Hyper-refractive areas 16 present the later stages (Figures 4 and 5B). The vascular network of the Stage 1 1 CNVM and the scarring stage with a dramatic and exemplary Stage 2 5 network of larger and smaller blood vessels across different Stage 3 5 quadrants were seen. The vessels seen in these stages in the Stage 4 3 outer retina were not always well delineated in the superficial Stage 5 2 and deeper networks, suggesting a wider area of involvement 40 eyes absent than expected (figure 5B). Cystoid spaces 15 eyes present Stage 1 6 Choroid layer Stage 2 4 The normal layer of choriocapillaris showed a diffuse granular Stage 3 2 texture of alternating dark and bright areas. The initial stages of Stage 4 3 the disease showed no changes except for some dark grey areas Stage 5 0 in cases with inner segment and outer segment (IS/OS) disrup- 41 eyes absent tion and large areas of intraretinal cavitation. The later stages BCVA, best-corrected visual acuity; CFT, central foveal thickness; IS/OS, inner segment with RPE hyperplasia and CNVM scarring showed bright areas and outer segment. with altered choroidal architecture that was porous with a

1484 Chidambara L, et al. Br J Ophthalmol 2016;100:1482–1488. doi:10.1136/bjophthalmol-2015-307941 Downloaded from http://bjo.bmj.com/ on November 15, 2016 - Published by group.bmj.com Clinical science

Figure 3 (A) Stage1: Colour fundus photo showing dull foveal reflex and optical coherence tomography (OCT) reveals intraretinal hyporeflective spaces with changes in photoreceptor layer. OCT angiography (OCTA)-macular telangiectasia type 2 (MacTel2) showing mild irregularity of the foveal avascular zone (FAZ) and minimally increased intervascular spaces more in the superficial plexus (*) and broken regular network of FAZ with broken twig like capillaries at deep plexus (arrowhead). All other layers appear normal and so are not illustrated. (B) Stage 2: Colour fundus photo showing altered fovea with slight greying of perifoveal area with OCT showing intraretinal hyporeflective spaces and internal limiting membrane drape at the fovea. On OCTA, besides stage 1 changes, there is progressive temporal enlargement and capillary rarefaction of FAZ in superficial layers (dotted circled area).Deep layer shows decrease in perifoveal capillary density but more pronounced and brighter capillary twigs, lost FAZ ring (dotted circle) and few aneurysmal dilatations (arrow). Outer retina and choroid appears uninvolved. (C) Stage 3: Colour fundus image showing vascular telangiectasia with greying of perifoveal retina. OCT shows decreased central foveal thickness, intraretinal hyporeflective spaces and photoreceptor loss. OCTA shows gross segmental loss of perifoveal capillary network, more temporally in both superficial and deep layers with increase in the FAZ and also noticeable distortion, more in the deeper plexus (dotted circled area). The right-angled vessel dipping can be appreciated and traced from superficial to deep plexus (red arrows). Outer retina and choroid were uninvolved.

sponge-like or coral-like appearance with prominent larger controls (p<0.01, table 2). There was a positive and statistically vessels that seem embedded in the substance of choroid with a significant relationship (r=0.441) between the superficial capil- network of interspersed finer vessels corresponding to the area lary density and deep capillary density in patients (figure 6). of the scar and the changes seen in the other layers (figure 5B). DISCUSSION Capillary density MacTel 2 is a bilateral disease with characteristic alterations in The mean capillary density calculated by the Ex_GUI in patients the macular capillary network with neurosensory atrophy.1 The with MacTel 2 was 39.99%±3.9% and 39.03%±4.54% in the hallmarks of the disease include hyporeflective intraretinal cavi- superficial layer and deep layer, respectively. The corresponding tations, foveal thinning, abnormal vascular anastomosis, RPE mean capillary density in controls was 45.18%±0.84% and hyperplasia, CNVM, formation and vision-threatening progres- 44.21%±0.85%, respectively. There was a significant difference sive photoreceptor loss primarily attributed to the pathophysio- between the capillary density in patients with MacTel 2 and logical and biochemical changes involving the Müller cells.18

Chidambara L, et al. Br J Ophthalmol 2016;100:1482–1488. doi:10.1136/bjophthalmol-2015-307941 1485 Downloaded from http://bjo.bmj.com/ on November 15, 2016 - Published by group.bmj.com Clinical science

Figure 4 Stage 4: Colour fundus photo showing pigment clumps and retinal pigment epithelium (RPE) alteration at macula. Optical coherence tomography (OCT) shows intraretinal hyper-reflectivities with backscattering and disruption of photoreceptor layer with variable retinal thinning. OCT angiography (OCTA) shows increased foveal avascular zone diameter and intervascular spaces, more horizontally with complete loss of perifoveal regular capillary meshwork in the superficial and deep layers with prominent larger vessels. A brush-like localised branching of vessels (dotted circles) with right-angled dipping can be seen around darker areas (arrows) suggestive of RPE hyperplasia. Outer retina reveals blood vessels corresponding to areas around RPE hyperplasia (arrows). Choroid reveals dark areas surrounded by gross alteration of texture surrounding it. Red arrows depict the anastomosis between the superficial and deep layers.

Presentation is after the fourth decade and the age in our cohort The abnormal vascular anastomosis described by Chin et al15 in ranged from 42 to 75 years (60±5.2). MacTel group found the earlier stages were seen in our study as well. OCTA observations mean age of presentation to be 61±9 years.13 Other studies also in our study have a positive correlation with earlier histopatho- showed mean age of presentation as 58±8 years.10 Spaide logical studies16 that showed thickening of retinal capillaries, et al11 had an average age of 61.9 years. There was female sex proliferation of the basement membrane in a multilayer config- predilection of 71.4% in our study which was similar to uration especially in the deep layer evident as brighter and more Clemons et al13 group, while Nowilaty et al14 had an equal pronounced blood vessels in the perifoveal FAZ. Spaide et al11 distribution. showed changes in the inner and outer retinal plexus such as tel- OCT features seen in our cohort such as IS/OS disruption, angiectatic vessels with increased intervascular spaces, and the hyporeflective areas in the inner retinal layers and pigment patchy loss of capillary network that began temporally and pro- plaques are similar to earlier studies.39The OCTA features that gressed with advanced stages which was seen in our cohort as we appreciated in the deep and superficial networks such as well. abnormal vascular anastomosis and loss of capillaries have been Imaging modalities like FA and OCT can help in gross estima- described on fundus FA and OCT by Yannuzzi et al.3 tion of changes in the vascular network. Limited visualisation of

1486 Chidambara L, et al. Br J Ophthalmol 2016;100:1482–1488. doi:10.1136/bjophthalmol-2015-307941 Downloaded from http://bjo.bmj.com/ on November 15, 2016 - Published by group.bmj.com Clinical science

Figure 5 (A) Stage 5: A predominantly scarred neovascular membrane due to macular telangiectasia type 2 as seen on colour fundus photo, mid-phase frame of fluorescein angiography and optical coherence tomography scan. (B)Stage 5: Superficial and deep layers show complete distortion of foveal avascular zone, gross capillary rarefaction and dilated vessels that can be traced through different layers with abnormal anastomosis (dotted circles). Outer retina shows dense vascular network corresponding to the area of the scar (dotted circles) with an additional area of network of vessels (arrow) not corresponding to other layers suggestive of extensive areas of involvement. Choroid shows gross alterations in the texture with porous/spongy appearance, larger blood vessels with interspersed finer vessels in the area of the scar (larger dotted circle). Red arrows depict the anastomotic vessels between the superficial and deep network.

the deeper retinal layers on FA compounded by obscuration of the OCTA clearly depicts the vascular network, pattern of loss finer details due to dye leakage prevents more detailed analysis. and sectoral involvement, thereby providing a better under- OCTA has the unique advantage of allowing visualisation of the standing of the pathogenesis of the disease with finer visualisa- pathology at various retinal layers in vivo,17 mimicking histo- tion. A combination of both the modalities may be an pathological sections. The superficial as well as deep vascular alternative to invasive FA. plexus showed almost equal involvement with a slight prepon- derance of deep vessel involvement.316In order to quantify our findings, capillary density at various retinal layers was calculated with indigenously developed software. There was a significant CONCLUSION reduction in the capillary density in both the superficial and OCTA is a non-invasive, novel-imaging tool with in vivo deep layers when compared with age-matched controls. In our imaging properties that are comparable with histopathological study, there was a good correlation (r=0.441) between changes sections and helps in a better understanding of the pathogenesis, that were seen at both superficial and deep levels. Outer retina prognostication of the disease and improved standard of care. was a vessel-free area except in the later stages where there was The expanded indications of OCTA will be evident after its use an invasion of vessels. The retinal vascular changes begin in the in other retinal disease is validated. superficial regions and penetrate into the deep layers progres- sively. A further quantification of parameters with advances in imaging software would confirm this hypothesis. The present limitations of OCTA are a reduced field of imaging and difficult quantification, which would be overcome with advances in ana- lysis software and technology. Since MacTel is a pathology that involves the central retina, this was not a particular limitation in our study. The OCTA uses flow dynamics,12 while the OCT works on the principle of low coherence interferometry,18 giving only the structural details which is static in nature. The en face view of

Table 2 Mean capillary density in normal individuals and patients with macular telangiectasia (MacTel) Capillary density (mean) MacTel Normal p Value

Superficial 39.99 45.18 0.00** Deep 39.03 44.21 0.00** Outer retina 29.18 18.71 0.00** Figure 6 The relationship between superficial capillary density and n=66. deep capillary density. Circles represent individual subjects in the study **p<0.01. and the line represents the Pearsons correlation coefficient.

Chidambara L, et al. Br J Ophthalmol 2016;100:1482–1488. doi:10.1136/bjophthalmol-2015-307941 1487 Downloaded from http://bjo.bmj.com/ on November 15, 2016 - Published by group.bmj.com Clinical science

Competing interests None declared. 9 Sallo FB, Peto T, Egan C, et al. “En face” OCT imaging of the IS/OS junction line in type 2 idiopathic macular telangiectasia. Invest Ophthalmol Vis Sci Patient consent Obtained. 2012;53:6145–52. Provenance and peer review Not commissioned; externally peer reviewed. 10 Barthelmes D, Gillies MC, Sutter FK. Quantitative OCT analysis of idiopathic Ethics approval Institutional Ethics committee approval has been received for the perifoveal telangiectasia. Invest Opthalmol Vis Sc 2008;49:2156. imaging study based on OCTA. 11 Spaide RF, Klancnik JM, Cooney MJ. Retinal vascular layers in macular telangiectasia type 2 imaged by optical coherence tomographic angiography. JAMA Ophthalmol 2015;133:66–73. REFERENCES 12 Jia Y, Tan O, Tokayer J, et al. Split-spectrum amplitude-decorrelation 1 Gass JD, Oyakawa RT. Idiopathic juxtafoveolar retinal telangiectasis. Arch angiography with optical coherence tomography. Opt Express 2012;20: Ophthalmol 1982;100:769–80. 4710–25. 2 Gass JD, Blodi BA. Idiopathic juxtafoveolar retinal telangiectasis. Update of 13 Clemons TE, Gillies MC, Chew EY, et al. Baseline characteristics of participants in classification and follow-up study. 1993;100:1536–46. the natural history study of macular telangiectasia (MacTel) MacTel Project Report 3 Yannuzzi LA, Bardal AM, Freund KB, et al. Idiopathic macular telangiectasia. Arch No. 2. Ophthalmic Epidemiol 2010;17:66–73. Ophthalmol 2006;124:450–60. 14 Nowilaty SR, Al-Shamsi HN, Al-Khars W. Idiopathic juxtafoveolar retinal 4RyanS.Retina. 5 edn. London: Saunders, 2013, Chapter 42, Macular telangiectasis: a current review. Middle East Afr J Ophthalmol 2010; telangiectasia, 2015:1050–6. 17:224–41. 5 Wolff B, Basdekidou C, Vasseur V, et al. “En face” optical coherence tomography 15 Chin EK, Kim DY, Hunter AA, et al. Staging of macular telangiectasia: imaging in type 2 idiopathic macular telangiectasia. Retina 2014;34:2072–8. power-Doppler optical coherence tomography and macular pigment optical density. 6 Maruko I, Iida T, Sekiryu T, et al. Early morphological changes and functional Invest Ophthalmol Vis Sci 2013;54:4459–70. abnormalities in group 2A idiopathic juxtafoveolar retinal telangiectasis using 16 Green WR, Quigley HA, de la Cruz Z, et al. Parafoveal retinal telangiectasis: light spectral domain optical coherence tomography and microperimetry. Br J Ophthalmol and electron microscopy studies. Trans Ophthalmol Soc UK 1980;100(Suppl 2008;92:1488–91. 5):162–70. 7 Sallo FB, Leung I, Clemons TE, et al. multimodal imaging in type 2 idiopathic 17 de Carlo TE, Romano A, Waheed NK, et al. A review of optical coherence macular telangiectasia. Retina 2015;35:742–9. tomography angiography (OCTA). Int J Retin Vitr 2015;1:14354–15. 8 Charbel Issa P, Gillies MC, Chew EY, et al. Macular telangiectasia type 2. Prog 18 Fercher AF. Optical coherence tomography—development, principles, applications. Retin Eye Res 2013;34:49–77. Z Med Phys 2010;20:251–76.

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Characteristics and quantification of vascular changes in macular telangiectasia type 2 on optical coherence tomography angiography Lavanya Chidambara, Santosh G K Gadde, Naresh Kumar Yadav, Chaitra Jayadev, Devanshi Bhanushali, Abhishek M Appaji, Mukunda Akkali, Aruj Khurana and Rohit Shetty

Br J Ophthalmol 2016 100: 1482-1488 originally published online January 28, 2016 doi: 10.1136/bjophthalmol-2015-307941

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