Purpose: To develop and assess a method for quantitation of lower tear meniscus height (TMH) with the Kowa DR-1α tear interferometer.
Methods: Sixty-nine eyes of 49 men and 20 women (36 healthy volunteers, 33 patients with aqueous-deficient dry eye [ADDE]; mean age ± SD, 50.0 ± 14.0 years) were enrolled. TMH of each subject was measured by two observers both with DR-1α and newly developed software and with anterior-segment swept-source optical coherence tomography (SS-OCT). Intraoperator repeatability and interoperator and intersession reproducibility of measurements were assessed based on the within-subject SD (Sw), coefficient of variation (CV), and intraclass correlation coefficient (ICC). Agreement between the two devices was assessed by regression and Bland-Altman analysis.
Results: The CV for system repeatability of DR-1α was <2.0%. The CV for intraoperator repeatability and interoperator and intersession reproducibility for DR-1α measurements was ≤9.6%, ≤4.5%, and ≤4.4% in healthy subjects, respectively, and ≤16.8%, ≤9.8%, and ≤10.3% in ADDE patients. All corresponding ICC values were ≥0.87 in healthy subjects and ≥0.48 in ADDE patients. Bland-Altman plots indicated a high level of agreement between the two devices. Schirmer test value was significantly correlated with interferometric TMH in both healthy subjects (β = 0.59, P < 0.001) and ADDE patients (β = 0.47, P = 0.017).
Conclusions: Tear interferometry allows measurement of TMH as reliably as does SS-OCT. DR-1α may inform not only the diagnosis of dry eye disease but also identification of disease subtype.