In order to accurately study the morphology of the chorioretinal involvement in TB MSC, it is important to obtain color fundus photography at regular intervals. This greatly aids in the analysis of the fundus lesions and provides an objective assessment of change in the lesions over an extended period of time. Serial fundus photography (from acute stage to the stage of healing) is very useful in assessment of morphological evolution of the lesions [5]. In addition, color fundus photography can enable detection of other features such as vitreous haze among patients with intraocular TB. Careful analysis of fundus photographs may also help in the detection of complications such as development of choroidal neovascular membranes.

Studies have shown that fundus autofluorescence (FAF ) is a very useful noninvasive imaging modality in the management of TB MSC. Using FAF, the lesions can be assessed as they evolve from the acute stage to the stage of healing. Lesions of TB MSC can be staged using FAF imaging to determine the response of therapy as well as determine the natural course of the lesions (Fig. 8.3) [8]. Active lesions demonstrate ill-defined hyper-autofluorescence throughout the lesions. Thus, the lesions have a diffuse, amorphous appearance (Stage 1). In the stage of early healing (Stage 2), a thin rim of hypo-autofluorescence is seen surrounding the lesion which remains predominantly hyper-autofluorescent with a stippled pattern. With further healing, the lesion becomes predominantly hypo-autofluorescent (Stage 3) on FAF imaging. On complete healing, the lesions become uniformly hypo-autofluorescent without hyper-autofluorescent areas (Stage 4) [8].

Ultrawide-field fundus imaging is a recent addition in the imaging modalities used for the assessment of various chorioretinal pathologies (Fig. 8.3). Compared to conventional imaging (fundus photography and fluorescein angiography), ultrawide-field imaging systems aid in detection of additional features such as perivascular choroiditis, retinal vasculitis, and retinal neovascularization [9]. This imaging technology can be very useful in the management of TB MSC with modalities such as laser photocoagulation in areas of non-perfusion as well as to monitor the overall response to treatment on successive visits.

In addition, ultrawide-field imaging may be superior to conventional imaging in identifying changes such as peripheral paradoxical worsening (worsening of the primary disease upon initiation of anti-TB therapy due to possible release of antigens from the mycobacteria; ocular Jarisch-Herxheimer reaction) which may be otherwise missed on conventional imaging [9].

Fluorescein angiography (FA) is a very useful modality in the diagnosis and follow-up of patients with TB MSC. The active lesions of TB MSC appear hypofluorescent in the early phase and show hyperfluorescence in the late phase. In the natural history of the disease (without any therapy), the lesions may progress to become confluent, and the advancing edge shows early hypofluorescence with late hyperfluorescence. Due to retinal pigment epithelial damage and choriocapillaris atrophy, the areas of healing may demonstrate window defects on FA [5]. Thus, FA is very helpful in demonstrating the activity of the lesions of TB MSC. In addition, complications of the disease such as inflammatory choroidal neovascularization may be detected using FA, though it may be very challenging in the absence of high index of suspicion [10].

Ultrawide-field FA is very useful in the management of intraocular TB. In comparison with conventional FA, ultrawide-field imaging can reveal additional information such as peripheral capillary non-perfusion areas, retinal neovascularization, and retinal vascular leakage. Such findings may alter treatment decisions such as the need for scatter laser photocoagulation [9]. In the recent times, ultrawide-field FA is being increasingly used in the management of TB MSC.

The proper evaluation of TB MSC is incomplete without performing ICGA. Active lesions of TB SLC remain hypofluorescence from early to late phase on ICGA. ICGA is very useful in detecting choriocapillaritis and presence of choriocapillaris hypoperfusion among patients with TB MSC. Other changes of tubercular uveitis include presence of numerous hyperfluorescent spots, fuzzy appearance of choroidal vessels in the intermediate phase, and late choroidal hyperfluorescence due to dye leakage which tends to regress after completion of treatment with antitubercular therapy and corticosteroids. The ICGA changes are usually reversible and may be used to monitor the response to therapy [11–13]. The lesions of TB MSC may heal and result in development of choriocapillaris atrophy, which presents with early hypocyanescence followed by iso-cyanescens in the late phase.

Spectral-domain OCT has provided numerous insights into the pathogenesis of TB MSC. Various manifestations of chorioretinal involvement in TB MSC include peripapillary retinal atrophy, disruption of the photoreceptor and other outer retinal layers, thinning of retinal pigment epithelium, mild cystic changes as well as subretinal fibrosis in area of old choroidal neovascularization, and marked attenuation of the interdigitation zone in the outer retina [14, 15]. Lesions of TB MSC may also result in alteration of the ellipsoid and the myoid zones in the outer retina along with choriocapillaris thinning. In the acute stage of TB MSC, active edges of the lesions show localized, fuzzy area of hyper-reflectivity in the outer retinal layers involving the retinal pigment epithelium, photoreceptor outer segment tips, external limiting membrane, and the outer nuclear layer without increased backscattering from the inner choroid. As the lesions begin to heal from the center, the hyper-reflective fuzzy areas begin to disappear and are replaced by irregular, hyper-reflective knobbly elevations of the outer retinal layers. There is an increased reflectance from the choroidal layers due to attenuation of the retinal pigment epithelium-photoreceptor complex. As the lesions continue to heal further, there is loss of retinal pigment epithelium and outer retinal layers and persistent increased reflectance from the choroid on OCT. [16]