Chemical Injury — Classification & Grading

Roper-Hall Classification

The Roper-Hall classification is the traditional, most widely taught grading system for chemical ocular surface injuries. It stratifies severity based on two findings assessed together: the degree of corneal clarity (or haze) and the extent of limbal ischemia. Combining those two signs assigns a prognostic grade from Grade I, the best, to Grade IV, the worst.

Grade I injuries show a clear cornea with no limbal ischemia at all, correlating with an excellent visual prognosis. As grade increases, corneal haze progressively obscures iris detail and a greater circumferential extent of the limbus becomes ischemic (pale and blanched rather than perfused and pink), and the visual prognosis worsens correspondingly. The key conceptual point worth remembering is why these two findings, and not something like visual acuity or pain level, were chosen as the grading criteria: corneal clarity reflects direct optical-axis damage, while limbal ischemia reflects damage to the stem cell population the cornea depends on to ever heal — so together they capture both the immediate injury and the eye's capacity to recover from it.

Dua Classification

The Dua classification is a more modern refinement of Roper-Hall, designed to grade severity with finer resolution — particularly useful for the more severe injuries that Roper-Hall's four grades tend to lump together. The Dua system grades chemical ocular surface burns based on the number of affected clock hours of limbal involvement, combined with the percentage of conjunctival involvement. By quantifying limbal involvement in clock hours (rather than a qualitative "ischemic vs. not") and pairing it with a conjunctival involvement percentage, Dua offers finer gradation than Roper-Hall, especially for the severe end of the spectrum where Roper-Hall's Grade IV becomes a wide bucket covering very different actual burden of injury.

Conjunctival and Limbal Prognostic Signs

At the bedside, before any formal grade is calculated, two visual cues do most of the initial prognostic work.

Limbal ischemia (blanching)

In a chemical injury, limbal ischemia and blanching is a poor prognostic sign — the opposite of what intuition about a "calmer-looking" eye might suggest. Whitening of the limbus indicates ischemia of the limbal stem cells, which are the exact population of cells the cornea depends on for its own epithelial healing (see the Sequelae & Long-Term Management page in this series for what happens when that population is lost entirely).

Conjunctival redness vs. blanching

Counterintuitively, an inflamed and red conjunctiva is often a better prognostic sign than a white conjunctiva in chemical burns. Redness signifies ongoing blood supply to the tissue, while a white, blanched conjunctiva means the tissue has been damaged badly enough to lose its blood supply — ischemia, not "the eye having self-cleaned" or any reassuring process. In other words, in the acute chemical-burn exam, a red eye is the reassuring finding and a white eye is the alarming one — a reversal of how redness usually reads in ophthalmology.

Acid vs. Alkali: Overall Prognosis

Putting the grading systems together with the pathophysiology covered on the companion Pathophysiology page: alkali burns carry a worse overall visual prognosis than most acid burns. Alkali burns penetrate more rapidly and deeply due to liquefactive necrosis, causing greater damage to the cornea, anterior chamber, and intraocular structures — which is exactly what pushes an injury toward a higher Roper-Hall grade or a wider Dua clock-hour/percentage involvement, and toward a worse eventual outcome.

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