Reliability of grading lissamine green conjunctival staining.

Purpose: To assess the reliability of a lissamine green grading scale for conjunctival images.
Methods: A 20-second video clip of the right eye of 288 contact lens-wearing individuals was recorded using a digital slip-lamp camera after instilling liquid lissamine green. A single nasal and temporal still image were selected. A masked reader used the Oxford grading scale to grade the images on two occasions whereas a second masked reader graded each image on 1 occasion. kappa statistics and 95% confidence intervals (CIs) were used to determine the within- and between-grader reliability overall and when the sample was stratified by age, sex, contact lens type, and disease severity.
Results: There was substantial within-grader reliability for both the nasal (kappasimple = 0.69, 95% CI, 0.63-0.75) and temporal (kappasimple = 0.73, 95% CI, 0.67-0.79) images. There was moderate between-grader reliability for both the nasal (kappasimple = 0.51, 95% CI, 0.44-0.58) and temporal (kappasimple = 0.51, 95% CI, 0.44-0.58) images. Age, sex, and contact lens type did not affect within- or between-examiner reliability. There may have been an influence of disease severity on within-examiner reliability, because grading of the temporal images was significantly less reliable in the images with more significant staining.
Conclusion: Within- and between-grader reliability of lissamine green staining seems to be at least substantial to moderate. Because the extent of conjunctival staining may influence reliability, this should be considered when studies may include patients with significant staining.