Immune ring is a feature of -
A sterile immune ring (yellow line of demarcation)may be present where fungal antigen and host antibodies meet.Its a sign in fungal corneal ulcer Reference:Comprehensive ophthalmology,AK Khurana,6th edition,page no.106
Interstitial keratitis
Fungal corneal ulcer
Bacterial corneal ulcer
Herpes simplex keratitis
Cornea and sclera