Imaging Features of Herpetic Interstitial Keratitis by Anterior Segment Optical Coherence Tomography

Herpes simplex virus (HSV) and varicella zoster virus (VZV) are known causes of chronic and recurrent interstitial keratitis. Determination of active corneal inflammation is important for appropriate management. This study aimed to investigate features of clinically active herpetic interstitial keratitis (HIK) by anterior segment optical coherence tomography (AS-OCT).

Twenty-seven patients with active HIK (17 with HSV, 10 with VZV) and AS-OCT imaging were retrospectively identified. Five patients also had stromal scarring (SS), presumably from prior HIK episodes. An additional 4 patients with SS, but without a history of HIK, were also identified. The AS-OCT images were analyzed qualitatively, followed by an automated segmentation analysis. Deidentified images were shown to 3 masked graders after a training module, and their diagnoses were compared with slit-lamp diagnoses.

Qualitative analysis of AS-OCT images of active HIK revealed anterior stromal hyperreflectivity, often with a hazy border and convex posterior contour comparable with "posterior bowing" historically seen on slit lamp. Borders were sharper and typically more linear for SS. Automated segmentation analyses identified that epithelium overlying the stromal area of interest was thicker in SS than HIK. Survey results revealed a high degree of correlation with slit-lamp diagnoses.

AS-OCT may be a useful adjunct to slit-lamp examination in the evaluation of active inflammation in patients with a history of HIK. Hyperreflectivity, hazy borders, convex contour, and epithelial thickness may be informative. Future studies could elucidate a role for deep learning algorithms in diagnosing active HIK.