How red is a white eye? Clinical grading of normal conjunctival hyperaemia

Abstract

Purpose: To quantify the level of normal bulbar conjunctival hyperaemia using the Cornea and Contact Lens Research Unit (CCLRU) grading scale, and to investigate inter-observer agreement. Methods: Bulbar conjunctival hyperaemia was assessed by two trained observers, using the CCLRU grading scale (zero to four units) interpolated into 0.1 increments, on the right eye of 121 healthy, non-contact lens-wearing subjects (male=58, female=63, median age=28 years, range 16-77). The eye was observed using a slit-lamp bio-microscope (× 10 magnification) under diffuse, white illumination. The subject's position of gaze was directed to allow grading of four quadrants: superior, nasal, inferior, and temporal conjunctiva. Bulbar redness was defined as the average of those four grades of conjunctival hyperaemia. A further twenty subjects were recruited to assess inter-observer agreement (male=8, female=12, median age=23 years). Results: The average bulbar redness was 1.93 (±0.32 SD) units. The nasal (2.3±.4) and temporal (2.1±0.4) quadrants were significantly redder than the superior (1.6±0.4) and inferior (1.7±0.4) quadrants (P<0.0001). Males had redder eyes than females by 0.2 units. Inter-observer 95% limits of agreement for bulbar redness was 0.38 units. Conclusions: The average bulbar redness of 1.9 units was higher than expected, reflecting the design of the grading scale. A bulbar redness of greater than 2.6 units may be considered abnormal, and a change in bulbar redness of ≥0.4 units may be significant.