Classifying the severity of corneal ulcers by using the "1, 2, 3" rule.

Purpose: To propose and define the "1, 2, 3" rule as a system of categorizing the severity of bacterial keratitis and to determine its value in predicting the likelihood of visual loss after healing of bacterial corneal infection.

Methods: Seventy patients were evaluated for infectious corneal ulcers by 2 cornea subspecialists (J.D.L., M.C.V.) at a tertiary facility between October 30, 2001, and November 1, 2004. Forty-one patients met the inclusion criteria. Visual acuities, ulcer characteristics, culture results, and treatment data were collected.

Results: The sensitivity of the "1, 2, 3" rule for detecting potentially sight-threatening (PST) ulcers that would result in 0.20 logMAR (2 Snellen lines) or greater loss in best spectacle-corrected visual acuity (BSCVA) was 100%. The specificity of the "1, 2, 3" rule in correctly labeling an ulcer that did not cause vision loss as rarely sight threatening (RST) was 57.14%. The positive predictive value of the "1, 2, 3" rule was 28.57%. The negative predictive value of the "1, 2, 3" rule was 100%.

Conclusions: Corneal ulcers classified as PST are at significantly higher risk for sustaining loss of BCSVA compared with RST corneal ulcers. The "1, 2, 3" rule is sensitive and specific enough to be clinically useful in predicting which ulcers are more likely to have vision loss and which ulcers are not.