In Acanthamoeba keratitis, the pathognomonic slit-lamp finding that distinguishes it from herpes simplex keratitis or fungal keratitis in the early stage is:

• A Ring-shaped stromal infiltrate
• B White stromal infiltrate with feathery margins
• C Perineural infiltrates (radial keratoneuritis) ✓
• D Satellite lesions around the main ulcer

Explanation

The earliest and most characteristic sign of Acanthamoeba keratitis is perineural infiltrates (radial keratoneuritis) — infiltrates tracking along corneal nerves in a radial pattern. This reflects the organism's predilection for corneal nerves. The classic ring infiltrate appears later and is less specific. Feathery margins with satellite lesions suggest fungal keratitis. Dendritic ulcers suggest HSV. Identifying radial keratoneuritis early is critical because delayed diagnosis leads to severe outcomes; treatment with polyhexamethylene biguanide (PHMB) is most effective when started early.

Reference: Khurana Comprehensive Ophthalmology, 7th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.