Intraobserver Repeatability Assessment of the S390L Firefly WDR Slitlamp in Patients With Dry Eye Disease: Objective, Automated, and Noninvasive Measures

Objectives:To assess the intraobserver repeatability of automated, objective, and noninvasive measures obtained with the S390L Firefly WDR slitlamp.Methods:This cross-sectional study included 50 eyes of patients with dry eye disease with a mean age of 55.06 & PLUSMN;12.96 years. Three consecutively repeated measures of the following variables were obtained: first noninvasive break-up time (F-NIBUT), average noninvasive break-up time (A-NIBUT), tear meniscus height, tear meniscus area (TMA), nasal ciliary hyperemia (NCIH), temporal ciliary hyperemia (TCIH), nasal conjunctival hyperemia (NCOH), temporal conjunctival hyperemia (TCOH), upper loss area meibomian gland (U-LAMG), lower loss area meibomian gland (L-LAMG), upper meibomian gland dysfunction grade (U-MGD grade), and lower meibomian gland dysfunction grade (L-MGD grade). Intraobserver repeatability was estimated with coefficient of variation (CoV), intrasubject standard deviation (SD) (S-w), and Bland-Altman plots.Results:All variables showed no statistically significant differences in the repeated-measures analysis except for L-MGD grade (P=0.045). F-NIBUT and A-NIBUT obtained the highest CoV with an average value of 0.48 & PLUSMN;0.41 [0.02-1.00] and 0.34 & PLUSMN;0.25 [0.02-1.00], respectively. The remaining variables showed CoVs between 0.04 & PLUSMN;0.11 [0.00-0.43] and 0.18 & PLUSMN;0.16 [0.00-0.75]. A-NIBUT, TMA, NCOH, and L-LAMG obtained an S-w of 2.78s, 0.21 mm(2), <0.001, and 4.11%, respectively. Bland-Altman plots showed a high level of agreement between pairs of repeated measures.Conclusion:The S390L Firefly WDR slitlamp has moderate intraobserver repeatability for F-NIBUT and A-NIBUT, which suggests that F-NIBUT and A-NIBUT are tests with high variability. The remaining variables show satisfactory intraobserver repeatability.