Linear Interstitial Keratitis - A Retrospective Chart Review of a Rare Entity

BACKGROUND: Linear interstitial keratitis (LIK) is a rare variant of interstitial keratitis and is characterised by a sharply demarcated stromal band of opacity with uncertain pathophysiology and no consensus management. We report the largest contemporary study to characterise phenotype, diagnostics, treatment, and outcomes.

METHODS: This is a retrospective, investigator-initiated study across two university hospitals. Extracted data included demographics, clinical features, microbiology/serology, anterior segment imaging, treatments and outcomes.

RESULTS: Six unilateral cases were included (five males, one female). LIK presented as a sharply demarcated linear stromal opacity of variable, often near limbus-to-limbus, extent. AS-OCT commonly localised the lesion to the anterior stroma, while IVCM (when performed) suggested broader stromal activation, despite an anterior-predominant OCT signal. Corneal scraping, as well as systemic workup, was mostly unremarkable. Management frequently combined topical corticosteroids with topical antimicrobials and/or systemic antivirals. One patient received steroid-sparing maintenance with topical 0.1% cyclosporin. Visual outcomes were generally favourable: four eyes achieved or maintained corrected Snellen ≥ 1.0. However, two eyes declined (to 0.6 and 0.5), and one patient experienced two corneal perforations during a relapsing course.

CONCLUSIONS: LIK is a recognisable, predominantly anterior stromal, phenotype of interstitial keratitis affecting predominantly younger patients. An immune-stromal process is assumed, but a clear cause could not be established despite extensive testing. Most cases are steroid-responsive but may relapse, supporting slow tapering and consideration of steroid-sparing prophylaxis. Close monitoring is warranted when thinning, neovascularisation, or recurrence is present.