Validity of a new comprehensive pterygia grading scale for use in clinical research and clinical trial

To determine the reliability and agreement of a new comprehensive pterygium grading scale for use in clinical research and clinical trials.

Thirty eyes with pterygia were enrolled in this study. Primary gaze position and lateral gaze position images were taken of each eye with a modified single-lens reflex camera system. Our grading scale includes five parameters: two hyperemia parameters of pterygia on two different gaze position images and three size parameters, quantifying length, width, and area of the cornea encroachment of pterygium, using ImageJ software. All images were graded on the five parameters by two masked, certified reading center graders. Two graders independently graded all the images to determine inter-grader reliability. One grader regraded the images after 3 days to determine intra-grader reliability. Intraclass correlation coefficient (ICC) and inter-rater agreement statistic (κ) calculations were performed.

The intra-grader reliability for hyperemia grading was high on both primary and lateral gazing positions (κ value is 0.93 and 0.96). The inter-grader reliability for hyperemia grading was also good (κ value is 0.85 and 0.87). The mean value of width, length, and area of the cornea encroachment of pterygium was 4.31 ± 2.04 mm, 2.08 ± 1.43 mm, and 7.84 ± 7.62 mm², respectively. The intra-grader agreement on width, length, and area were excellent, with ICCs of 0.98 (95% CI 0.96-0.99), 0.99 (95% CI 0.98-1.0), and 0.97 (95% CI 0.94-0.99), respectively. The inter-grader agreement on width, length, and area were also excellent, with ICCs of 0.96 (95% CI 0.90-0.98), 0.99 (95% CI 0.98-0.99), and 0.99 (95% CI 0.97-0.99), respectively.

There was excellent intra- and inter-observer reproducibility with the new comprehensive grading scale. This scale could lead to the development of standardized grading assessments and quantification of pterygia that would be valid in clinical research and clinical trials.