DAY-TO-DAY VARIATIONS IN OCULAR SURFACE STAINING OF THE BULBAR CONJUNCTIVA

Purpose. The purpose of this study was to characterize the variability of bulbar conjunctival staining over time in response to a single app lication of fluorescein. Methods. 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 we tted with nonpreserved saline to the lower palpebral conjunctiva of ea ch eye, with the right eye being stained first. Immediately after appl ication of the fluorescein, conjunctival staining was graded in a rand omized order by two examiners, using cobalt blue illumination and a no . 15 Wratten enhancement filter. Conjunctival staining was assessed ba sed upon a 0 to 4 grading scale with 0.5 grade increments. By evaluati ng the variability in staining over time for each subject, a represent ation of overall fluctuation for the group was obtained. Results. The average duration for an episode of staining graded higher than the gro up median (grade 0.5) was found to be 2.0 +/- 2.4 days. Overall, a mea n 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 statis tically significant [p = 0.73, multi-way, repeated measures analysis o f variance (ANOVA)]. The mean difference in grading between the two ex aminers 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 corr elation). Conclusions. Characterization of conjunctival staining over time may be useful in evaluating clinically suspect staining, and in d etermining its potential duration. The appearance and variability of t he conjunctival staining patterns noted in this study indicate a poten tial relationship to normal physiological processes, such as desquamat ion. This study also demonstrated a low amount of variability between right and left eyes, supporting the use of contralateral studies in th e assessment of conjunctival staining. It also demonstrated a good con sistency between separate examiners despite not being standardized.