Tear lipid layer thickness with eye drops in meibomian gland dysfunction

Abstract

Purpose: The aim of this study was to evaluate the efficacy of a lipid containing emollient eye drop, Soothe XP, which was reformulated in 2014 with a more stable preservative and buffer system, compared to a control, non-emollient, eye drop (Systane Ultra) in improving lipid layer thickness (LLT) in subjects with dry eye due to meibomian gland dysfunction (MGD).

Patients and methods: This prospective single-center, open-label, cross-over, examiner masked-study enrolled subjects aged 30-75 years with lipid-deficient dry eye and a clinical diagnosis of MGD as determined by a slit lamp examination, an evaluation of meibomian gland drop out with meibography, and a standard patient evaluation of eye dryness questionnaire of >5. Eligibility was then determined by a LLT of <75 nm at baseline and the inability to increase LLT ≥15 nm with three blinks, as determined by interferometric methods. Subjects were randomized to receive a single emollient or non-emollient eye drop at Visit 1 and were crossed over for the alternate treatment at Visit 2. At each visit, LLT was measured prior to and 15 minutes following the instillation of the assigned eye drop. The primary endpoint was the change in LLT from baseline.

Results: Subjects (n=40) were enrolled and 35 completed the two study arms. Mean (±SD) patient age was 55.7 years (10.9) and 69% were female. Mean (±SD) LLT at baseline was 49.5 nm (9.2). Instillation of Soothe XP resulted in an increase in LLT to 77.5 nm (29.3) 15 minutes following drop instillation, which is an increase of 28.0 nm (27.4) (P<0.001). In contrast, LLT 15 minutes after the instillation of Systane Ultra was 50.8 nm (14.1), which was not statistically significant when compared to the baseline LLT.

Conclusion: In this study of subjects with MGD, the emollient, or lipid containing eye drop, increased the LLT of tears when measured 15 minutes after instilling a single eye drop.

Keywords: dry eye; emollient; interferometry; lipid; meibomian; thickness.

Figure 1

Study design. Abbreviations: LLT, lipid layer thickness; SPEED, standard patient evaluation of eye dryness.

Figure 2

LLT prior to and 15 minutes following a single drop of emollient or non-emollient eye drop in dry eyes with meibomian gland dysfunction. Data are the mean (±SD) LLT based on stroboscopic video color microscope (SVCM) measurements in study eyes (qualifying eye in subjects with only one qualifying eye, or the eye with the lowest LLT at baseline in subjects with two qualifying eyes). P<0.001 paired t-test for the change from baseline. Abbreviation: LLT, lipid layer thickness.

Figure 3

Percentage of study eyes with a clinically significant increase in lipid layer thickness 15 minutes following a single drop of emollient or non-emollient eye drop in dry eyes with meibomian gland dysfunction. A clinically significant increase was defined as an increase of ≥15 nm from baseline as determined by stroboscopic video color microscope interferometry. Note: P<0.001 chi-square test, two-tailed for the difference in percentages.

Figure 4

Representative stroboscopic video color microscope (SVCM) images of the lipid layer of the tears at the baseline qualifying visit (A); 15 minutes following instillation of a single drop of a non-emollient eye drop (B); and 15 minutes following the instillation of a lipid containing (emollient) eye drop (C). Note: Note that gray, or a lack of color, is representative of a thin lipid layer, whereas bright colors represent thicker lipid layers, as noted in the color scale beside each image.