The Effect of Medium Chain Triglycerides–Containing Tear Substitute on the Dynamics of Lipid Layer Interference Patterns (DLIP) in Dry Eye Patients

Abstract

Abstract: : Purpose: The lipid layer of the tear film in keratoconjunctivitis sicca (KCS) shows the inability to maintain a consistent interference pattern with repeated blinking while in the normal healthy eye it maintains a consistent pattern of interference among several blinks. The aim of the study was to evaluate the possibility of improving the consistency of dynamic lipid interference patterns (DLIP) in dry eyes by means of a lipid–containing tear substitute. Methods: Twenty patients with bilateral definite clinical diagnosis of dry eye (positive to at least two out of the following three tests: Schirmer I<5 mm/5 min, BUT<7 sec, positive lissamine green staining of the ocular surface) were enrolled for the study. All subjects underwent DLIP test which measures the number of blinks during which the precorneal tear film lipid layer maintains a definite interference pattern. The DLIP test was performed in a randomly chosen eye of each subject at three different times: 1) in basal condition (without instillation of any tear substitute), 2) 5 minutes after the instillation of a 0.2% carbopol tear substitute and 3) 5 minutes after the instillation of a 0.2% carbopol+medium chain triglycerides–containing tear substitute. The differences in the average number of blinks for each eye showing a consistent lipid layer interference pattern at the three different times of the experiment was statistically evaluated using Student t–test. Results: The number of blinks providing the same consistent lipid layer interference pattern of the tear film measured by means of DLIP test was increased both by carbopol only tear substitute and carbopol+triglycerides–containing tear substitute. In particular the KCS eyes showed an average of 2.3±1.5 blinks with consistent DLIP, KCS eyes after 0.2 carbopol instillation showed an average of 4.2±3.2 blinks with consistent DLIP(p<0.01) and KCS eyes after 0.2 carbopol+triglycerides containing tear substitute instillation showed an average of 8.2±3.4 blinks with consistent DLIP (p<0.001 vs. untreated KCS and p<0.01 vs. 0.2% carbopol treated KCS eyes). Conclusions: The presence of the medium chain triglycerides component in a carbopol tear substitute significantly improved the results of the DLIP test in dry eye patients. These results could be possibly due to the ability of triglycerides to be included in the polar structural portion of the tear film lipid layer with consequent improvement of its stability.

Keywords: cornea: tears/tear film/dry eye • clinical (human) or epidemiologic studies: systems/equipment/techniques