Double-Layer Sign: A New OCT Finding in Active Tubercular Serpiginous-like Choroiditis to Monitor Activity

To describe a novel spectral-domain (SD) OCT finding of a double-layer sign at the site of activity in tubercular serpiginous-like choroiditis (SLC) and how this sign can be used to assess treatment response in these eyes.

Retrospective, observational case series.

We retrospectively reviewed simultaneous fundus photographs and SD OCT and fundus autofluorescence (FAF) images of eyes affected with tubercular SLC from the acute stage until resolution of lesions using the Heidelberg Spectralis HRA and OCT system (Heidelberg Engineering, Heidelberg, Germany).

Occurence of the double layer sign (DLS) during activity; reduction in the double layer sign (DLS) with resolution of choroidal and retinal inflammation; correlation of SD OCT and FAF findings.

Five eyes of 5 patients were studied in detail. Spectral-domain OCT findings included choroidal elevation and a double-layer sign (separation of hyperreflective retinal pigment epithelium [RPE] from Bruch's membrane, with the gap between them showing moderate reflectivity) at the site of activity. This correlated with hyperautofluorescence with indistinct borders on FAF imaging. Reduction in the double-layer sign became evident as the lesions began to resolve, and eventually this area was replaced by hyperreflective, irregular, knobbly elevations of the RPE. In eyes with severe inflammation and increased choroidal elevation on OCT, the double-layer sign was very prominent. As the choroidal elevation decreased on OCT, increased reflectance from the choroidal layers was evident. As the lesions resolved, the lesions became predominantly hypoautofluorescent on FAF and loss of RPE, ellipsoid zone, and external limiting membrane on SD OCT scan became evident. Good correlation was found between the resolution of the double-layer sign on SD OCT and FAF findings.

The double-layer sign on SD OCT may be a useful finding in monitoring the activity in tubercular SLC. The OCT changes can be correlated with FAF imaging in these eyes.