A comparison of subjective and objective conjunctival hyperaemia grading with AOS® Anterior software

Abstract

Clinical relevance: This study evaluates a commercially available conjunctival hyperaemia grading system, providing validation of an important tool for ocular surface research and clinical trials.

Background: Bulbar conjunctival hyperaemia is a sign of ocular surface inflammation, and proper measurement is essential to clinical care and trials. The aim of this study was to assess the validity and repeatability of an objective grading system in comparison with subjective grading.

Methods: This study was a retrospective, randomised analysis of 300 bulbar conjunctival images that were collected at an academic institution. The images used were de-identified and collected from the Keratograph K5 and Haag-Streit slitlamp. Six investigators graded the images with either a 0.1 or 0.5 unit scaling using a 0-4 Efron grading scale. Three of the investigators also imported the images into the AOS ® Anterior software and graded them objectively. All measurement techniques were assessed for repeatability and comparability to each other.

Results: Mean hyperaemia with the objective system (1.1 ± 0.7) was significantly less than the subjective grading (2.0 ± 0.8) (P < 0.001). Both inter- and intra-subject repeatability of the objective system (0.15) was better than the subjective methods (1.70).

Conclusion: The results showed excellent repeatability of the AOS ® Anterior objective conjunctival hyperaemia grading software, although they were not found to be interchangeable with subjective scores. This system has value in monitoring levels of hyperaemia in contact lens wearers and patients in clinical care and research trials.

Keywords: Hyperaemia; Objective grading; Subjective grading; conjunctiva.

Figure 1.. The AOS ® Anterior software interface.

Images were uploaded into the AOS ® Anterior software and the examiner subjectively selected the region of interest (A). The vasculature was automatically traced by the software, and outputs of conjunctival redness and per cent vessel score are shown (B).

Figure 2.. Examples of Slit Lamp and Keratograph images with hyperemia grading.

Images taken with the slit lamp (A) and Keratograph (B) are shown for 0.1 subjective, 0.5 subjective, and 0.1 objective grading (columns). The images shown represent grading of approximately 1.0, 2.0 and 3.0 (rows). Exact mean grades of all examiners are shown in the lower right corner of each image. Note that for slit lamp imaging using the AOS® software, no images were scored greater than 3.0; the image shown was taken using a low luminance auxiliary light that caused falsely high reading with the objective system, and this images was among those that were excluded from final analysis.

Figure 3.

Box and whisker plots for each grader using the subjective and objective systems (n=263 images). Boxes show median hyperemia and interquartile ranges with the whiskers indicating the minimum and maximum values. Large ranges are seen due to the variability of redness levels of the images graded. Graders are identified by “G.”

Figure 4.

Bland-Altman plots showing differences versus means for various grading methods. Top row: within examiner comparison of subjective and objective grading for Graders 1, 2 and 3 (G1, G2, G3). Middle row: between examiner comparison of objective grading. Bottom row: comparison of all subjective and objective scales for all examiners. Dotted lines represent 95% confidence intervals. Bias and limits of agreement (LOA) are shown for each plot.