Day to day variations in ocular surface staining of the bulbar conjunctiva

The purpose of this study was to characterize the variability of bulbar conjunctival staining over time in response to a single application of fluorescein.

Sixteen subjects were stained Monday through Friday for a 2-week period. Appointments were scheduled from 9:00 a.m. to 12:00 p.m. to minimize variance due to diurnal variation. Fluorescein stain was applied by touching a separate Ful-Glo strip wetted with nonpreserved saline to the lower palpebral conjunctiva of each eye, with the right eye being stained first. Immediately after application of the fluorescein, conjunctival staining was graded in a randomized order by two examiners, using cobalt blue illumination and a no. 15 Wratten enhancement filter. Conjunctival staining was assessed based upon a 0 to 4 grading scale with 0.5 grade increments. By evaluating the variability in staining over time for each subject, a representation of overall fluctuation for the group was obtained.

The average duration for an episode of staining graded higher than the group median (grade 0.5) was found to be 2.0 +/- 2.4 days. Overall, a mean staining grade of 0.5 for the right eye and 0.6 for the left eye was found. Right and left eyes were found to correlate well (r = 0.67, p < 0.01, Spearman's correlation) and the mean difference was not statistically significant [p = 0.73, multi-way, repeated measures analysis of variance (ANOVA)]. The mean difference in grading between the two examiners was 0.1 grades (p = 0.67, multi-way, repeated measures ANOVA), with a correlation coefficient of r = 0.68 (p < 0.01, Spearman's correlation).

Characterization of conjunctival staining over time may be useful in evaluating clinically suspect staining, and in determining its potential duration. The appearance and variability of the conjunctival staining patterns noted in this study indicate a potential relationship to normal physiological processes, such as desquamation. This study also demonstrated a low amount of variability between right and left eyes, supporting the use of contralateral studies in the assessment of conjunctival staining. It also demonstrated a good consistency between separate examiners despite not being standardized.