New test to quantify lipid layer behavior in healthy subjects and patients with keratoconjunctivitis sicca

Diagnostic procedures currently available to evaluate tear film lipid layer alterations are of limited application and do not provide quantitative results. The purpose of this prospective, case-control study was to develop a noninvasive test to measure tear lipid behavior in healthy subjects and patients with dry eye.

The dynamic lipid layer interference patterns (DLIP) test was performed on 21 patients with dry eye and 21 age-matched controls. Subjects in the study and control groups were asked to perform 5 forced blinks and 10 consecutive nonforced blinks every 2 seconds to load lipids from the palpebral reservoir into the tear film. After recording the lipid layer interference patterns obtained with the Tearscope, a masked investigator counted the number of blinks to observe significant changes of shape, position, and number of waves of the interference patterns. Patients with dry eye were identified on the basis of the typical symptoms measured by a validated questionnaire (Ocular Surface Disease Index questionnaire score >10), Schirmer I test scores <10 mm/5 min, tear breakup time (TBUT) <7 seconds, and lissamine green conjunctival staining >4.

Significant differences in Schirmer test, TBUT, and lissamine green were recorded between groups. The DLIP test in the dry eye group (2.4 +/- 3.1 blinks) was statistically decreased compared with the control group (18.1 +/- 5.9 blinks; P < 0.0001, t test). A significant Pearson correlation (r = 0.788) was found between the DLIP test and TBUT. The receiver operating characteristic curve defined a cutoff value of 6.5 blinks to separate healthy from dry eyes (sensitivity of 100%, specificity of 95%).

The DLIP is a new test that can be used in clinical practice to quantify tear film lipid layer behavior and to diagnose dry eye.