Automated Measurement of Tear Meniscus Height with the Kowa DR-1α Tear Interferometer in Both Healthy Subjects and Dry Eye Patients

PURPOSE. To develop and assess a method for quantitation of lower tear meniscus height (TMH) with the Kowa DR-1 alpha 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 +/- 6 SD, 50.0 +/- 14.0 years) were enrolled. TMH of each subject was measured by two observers both with DR-1 alpha and newly developed software and with anterior-segment swept-source optical coherence tomography (SS-OCT). Intra-operator 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-1a was <2.0%. The CV for intraoperator repeatability and interoperator and intersession reproducibility for DR-1a 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 (beta = 0.59, P < 0.001) and ADDE patients (beta = 0.47, P = 0.017). CONCLUSIONS. Tear interferometry allows measurement of TMH as reliably as does SS-OCT. DR-1 alpha may inform not only the diagnosis of dry eye disease but also identification of disease subtype.