INTRODUCTION: Idiopathic macular telangiectasia (MacTel) is retinal capillary ectasia, which is limited to the perifoveal area. In 1982 Gass and Oyakawa classified  IJRT(idiopathic juxtafoveal retinal telangiectasia) into four groups based on clinical and fluorescein angiographic findings. In 1993 Gass and Blodi modified it-IJRT was subdivided into 3 groups and each group further into two subgroups.  Later Yanuzzi et al simplified Gass classification, correlating with findings in OCT, high speed Indocyanin Green and fluorescein angiography findings:

  (1)   aneurysmal telangiectasia or idiopathic macular telangiectasia type 1 which includes Gass 1A and 1B subgroups

  (2) perifovealtelangiectasia or idiopathic macular telangiectasia type 2 which includes Gass 2A sub-group.

Gass 2B and 3 groups were not included in that due to rarity of diseases. Chew et al classified MacTel 2 into non-proliferative (telangiectasia and foveal atrophy) and proliferative which shows  subretinal neovascularization (SRNV)¹.

Most common of these is MacTel type 2A. Idiopathic macular telangiectasia type 2 is a bilateral disease that affects men and women, mostly seen from fifth and sixth decades of life. MacTel type 2 (MacTel 2) is a bilateral disease characterized by changes in the capillary network and neurosensory atrophy. Slit lamp bio-microscopy reveals reduced retinal transparency, crystalline deposits, ectatic capillaries and blunted venules. Early features of the disease includes loss of transparency, superficial retinal crystalline deposits, right angled venules and presence of intra-retinal cystoid spaces in the fovea. In later stages, the intra-retinal pigment plaques and sub-retinal neovascular membrane develops. FFA (fundus fluorescein angiography) is considered as the gold standard for the diagnosis of MacTel, shows dilated, blunted right-angled veins, dilated capillaries in the deep retinal plexus, hyperfluorescence in the early and/or late phase. Optical coherence tomography (OCT) shows thinning of macula. In some cases cavitation in the inner retina or outer retina, or both is seen. A minority progress to develop full thickness macular holes. Stereoscopic color and red-free fundus photography shows loss of retinal transparency, inner retinal crystals, and in later disease pigment plaques in the mid retina. Several studies suggested that muller cell involvement is a main feature of MacTel2. OCTA (Optical coherence tomography angiography) is a newer noninvasive imaging modality which is found to be useful in MacTel. Progressive changes over time have been described in MacTel using each of the imaging techniques, but data on the correlation between signs apparent in these imaging modalities are very limited. Also very few studies are conducted on OCTA findings in MacTel.

This study plans to compare and correlate findings with symptoms  in various imaging modalities like SD-OCT (Spectral Domain-OCT), FAF (Fundus Auto Fluorescence), Multi-colour photography and OCTA in MacTel and also to monitor the progression in these biomarkers over one year period using multimodal imaging and to correlate it with vision.

REVIEW OF LITERATURE:

A retrospective review study conducted by Spaide et al on volume rendered angiographic and structural OCTA in MacTel-2 used multimodal imaging to evaluate right angle vein complexes, macular cavitation and deep retinal invasion and observed contractile features of the tissue in the temporal macula. Study states OCTA is useful in MacTel 2 to study vascular interrelationship and association with cavitation².

Luiz Roisman a, b., Philip J. Rosenfeld studied OCTA imaging in MacTel type 2 and observed OCTA is superior to other multimodal imaging³.

A cross-sectional study on characteristics and quantification of vascular changes in MacTel type 2 was conducted  by Chidambara et al in Asian Indian population, published in British Journal of Ophthalmology,  on 56  eyes of 28 patients  with MacTel 2  during a 3 month period  using fundus photography, SD-OCT,OCTA. FFA was done in indicated cases only. Mean capillary density was calculated using an automated software and found out that mean capillary density of the superficial and deep layers was reduced -39.99% and 39.03% in cases as against 45.18% and 44.21% in controls respectively. They concluded that OCTA helps to understand the pathology better⁴.

A Study by Sallo et al, published in Retina, the journal of retinal and vitreous diseases, which compared the different imaging modalities in macular telangiectasia Type 2. Signs in fundus fluorescein angiography, optical coherence tomography and dual-wavelength auto-fluorescence images were analyzed. One hundred and ninety-one eyes of 96 patients were studied.  Correlations between early and late fundus fluorescein angiography, luteal pigment loss and early/late fundus fluorescein angiography signs, inner and outer segment break length and pigment loss were significant. Fair correlation between pigment loss and retinal spaces/atrophic retinal restructuring observed. Bilateral symmetry was slight to substantial⁵.

Zhang et al conducted a prospective observational study to image sub-retinal neovascularization in proliferative macular telangiectasia type 2 (MacTel2) using swept source optical coherence tomography based micro-angiography (OMAG). Three eyes with neovascular MacTel2 were imaged with OMAG algorithm. It generated en face flow images from three layers of retina, as well as from the region bounded by the outer retina and Bruch’s membrane, the choriocapillaries, and the remaining choroidal vasculature. The OMAG images were then compared to images from fundus fluorescein angiography (FFA) and indocyanine green angiography (ICGA).The neovascularization was best identified from the en face OMAG images that included a layer between the outer retinal boundary and Bruch’s membrane⁶.

A  Case study was conducted to report the optical coherence tomographic angiography findings and response to treatment in a case of macular telangiectasia Type 2 with sub-retinal neovascularization by S.R.Sadda, patient was treated with intravitreal aflibercept, and they observed a remarkable reduction of flow in the sub-retinal neovascular network on optical coherence tomographic angiography⁷.

Lisa Toto, Luca Di Antonio by means of optical coherence tomography angiography (OCTA), studied morphologic features of idiopathic macular telangiectasia (MacTel) type 2 and then it was compared to findings of fundus fluorescein angiography (FFA), fundus auto-fluorescence (FAF), confocal blue reflectance (CBR), and spectral-domain OCT (SD-OCT)⁸.

AIMS AND OBJECTIVE:

AIM:-To study and monitor the progression in biomarkers in patients diagnosed with macular telangiectasia at GIRIDHAR EYE INSTITUTE, a tertiary eye care center in Kerala.

 OBJECTIVE:

1.       To assess the biomarkers in retina, in patients diagnosed with macular telangiectasia

2.       To assess the progression of the disease using multimodal imaging methods and correlate it with the symptoms if any and visual acuity.

 MATERIALS AND METHOD:

• Study area: Giridhar Eye Institute , Kochi
• Study population: OPD patients diagnosed with macular telangiectasia
• Inclusion criteria: all patients diagnosed with macular telangiectasia
• Study design: prospective observational study
• Sample size: 50 eyes

  FYI:   The sample size was calculated using the below formula

  ^where     Z_{1- α/2}       =     1.96

                                 p             =     Expected Proportion

                                            d             =    Absolute Precision

   The minimum sample size required is approximately 50 eyes.

Study duration: 18 months

METHODOLOGY

·         Symptomatic and asymptomatic patients who attend , who are diagnosed with macular telangiectasia have to be identified.

• To assess details and clinical history in detail.
• Then to do multimodal imaging with FFA as when needed to conform diagnosis, FAF,SD-OCT,MULTICOLOR IMAGING and OCTA
• All the same procedure (except FFA) is repeated at 6 months and  1year.

STATISTICAL METHOD:

• Data obtained from patients were recorded and analyzed using Microsoft Excel
• Results of categorical variables will be reported as counts and percentages
• McNemer’s test and Fishers exact test will be used to find the differences between categorical variables.