Diagnostic Role of Anterior Segment Optical Coherence Tomography in an Atypical Presentation of Varicella Zoster Virus Interstitial Keratitis: A Case Report.

BACKGROUND Varicella zoster virus (VZV) infection can involve various ocular structures with atypical manifestations. Distinguishing VZV interstitial keratitis from corneal intraepithelial neoplasia (CIN) is important to avoid unnecessary interventions. This report aims to demonstrate an unusual clinical presentation of VZV interstitial keratitis and present the value of various diagnostic tools in excluding CIN. CASE REPORT We describe the case of a 26-year-old woman with a right-eye corneal finding thought to be CIN. She had a history of unilateral headache, alopecia, loss of eyelashes, and redness on the right side over the past 5 years. Upon examination, she had normal vision, with a sectoral conjunctival injection and anterior stromal opacity. Anterior segment optical coherence tomography (AS-OCT) and epithelial mapping aided in the diagnosis of VZV interstitial keratitis. Treatment with oral valacyclovir and topical corticosteroids resulted in resolution of active keratitis within 1 month, with residual scarring. CONCLUSIONS This case report highlights the importance of considering infectious etiologies, including VZV, in atypical corneal lesions, and demonstrates the diagnostic value of AS-OCT in differentiating CIN. It also highlights the primary role of AS-OCT and epithelial mapping in providing diagnostic clues that can distinguish OSSN from other mimickers. Timely recognition of viral keratitis mimicking neoplasia prevents unnecessary surgical interventions and enables targeted antiviral therapy.