System used to describe alkali burns to eye. Grade 1Ñcorneal epithelial injury with no ischemia; grade 2Ñhazy cornea, iris details intact, ischemia < 1/3 of limbus; grade 3Ñcomplete corneal epithelial loss, blurring of iris details, ischemia 1/3Ð1/2 of limbus; grade 4Ñopaque cornea with obscured pupil or iris, ischemia > 1/2 limbus.