Study: Tear and meibum lipid profiles remain stable throughout day in healthy adult patients

A prospective lipidomic study published May 27, 2026, in Ophthalmic and Physiological Optics found that the dominant nonpolar lipid composition of tears and meibum remained largely stable from morning to evening in healthy adults.¹ The findings suggest that, in individuals without clinically apparent ocular surface disease, major tear film lipid classes may be relatively well regulated across the day despite known diurnal changes in ocular comfort and tear film performance.

The study focused on wax esters, cholesteryl esters, triglycerides, and several polar lipid classes. Clinically, the results are relevant because the tear film lipid layer contributes to optical surface quality, tear film spreading, and evaporative resistance, and altered meibomian gland lipid composition has been implicated in dry eye disease and meibomian gland dysfunction.^2-4

Study overview

Kumar and colleagues conducted a prospective study at the School of Optometry and Vision Science, University of New South Wales, Sydney, Australia.¹ Fifteen healthy non–contact lens wearers were enrolled, including 10 women and 5 men, with a mean age of 29.5 ± 11.6 years. Participants provided paired morning and evening samples, collected between 09:00 and 10:00 hours and between 16:00 and 17:00 hours.

Tear samples were collected with Schirmer strips without topical anesthesia. Meibum was expressed from the lower lid margin using a Korb expressor and collected with a sterile spatula under slit-lamp guidance. Lipids were extracted in chloroform and analyzed by liquid chromatography–mass spectrometry. The investigators quantified relative molar proportions of nonpolar lipid classes—wax esters, cholesteryl esters, and triglycerides—as well as polar lipids, including phosphatidylcholine, phosphatidylethanolamine, phosphatidylserine, sphingomyelin, lysophospholipids, ceramides, and diacylglycerols.¹

The primary analysis compared morning and evening proportions of lipid classes in tears and meibum. Paired comparisons used paired t tests or Wilcoxon signed-rank tests, as appropriate. The authors reported unadjusted P values and noted that multiple comparisons should be interpreted cautiously.¹

Key findings

In tear samples, nonpolar lipids accounted for nearly all measured lipids at both time points: 98.8% in the morning and 99.0% in the evening.¹ Wax esters were the most abundant tear lipid class, decreasing numerically from 55.6% ± 22.6% in the morning to 52.6% ± 22.7% in the evening. Cholesteryl esters were the next most abundant class, representing 38.4% ± 24.1% and 37.1% ± 20.1%, respectively. Triglycerides increased numerically from 3.9% ± 12.3% to 8.0% ± 18.1%, but the difference was not statistically significant.

Polar lipids represented a small fraction of the tear lipid profile, accounting for 1.2% in the morning and 1.0% in the evening. Phosphatidylcholine was the predominant polar lipid in tears. Overall, the investigators reported no significant morning-to-evening differences in relative proportions of individual tear lipid classes.¹

Meibum samples showed a similar pattern. Nonpolar lipids comprised 99.4% of meibum lipids in the morning and 99.2% in the evening. Wax esters were again the principal component, representing 73.3% in the morning and 72.8% in the evening, followed by cholesteryl esters at 25.3% and 24.3%, respectively. Triglycerides were higher in evening meibum, increasing from 0.72% to 1.9%.¹

Among polar lipids in meibum, diacylglycerols and phosphatidylserine were significantly higher in evening samples (P = .04 and P = .03, respectively). Other measured polar lipids did not differ significantly between time points.¹

Clinical context and interpretation

Dry eye disease is characterized by loss of tear film homeostasis, with tear film instability, hyperosmolarity, ocular surface inflammation, damage, and neurosensory abnormalities contributing to symptoms.² The lipid layer, largely supplied by the meibomian glands, helps support tear film spreading and may reduce evaporation.^3,4 Patients frequently report worsening ocular comfort later in the day, particularly with prolonged digital device use or other environmental exposures.⁵

This study suggests that, at least in healthy young adults, end-of-day ocular surface changes may not be explained by broad shifts in the major nonpolar lipid classes. The statistically significant changes were limited to low-abundance meibum lipid fractions, which the authors described as potential molecular-level modulation rather than a change in the dominant lipid profile.¹

Limitations and future research

The study was small and included only 15 healthy participants. The cohort excluded contact lens wearers and individuals with known ocular surface disease, limiting generalizability to patients with dry eye disease, meibomian gland dysfunction, or contact lens discomfort. The authors also noted that subclinical dry eye could not be fully excluded because comprehensive standardized dry eye testing was not performed.¹

Sampling was limited to 2 time points, which may miss more complex diurnal patterns. Tear collection always preceded meibum collection, and although a 10-minute washout period was used, residual procedural effects cannot be ruled out. Future studies should include larger and more heterogeneous cohorts, validated symptom questionnaires, clinical tear film assessments, and sampling during periods of active discomfort to clarify whether subtle lipidomic changes correlate with symptoms or disease states.¹

References:

1. Kumar M, Raj A, Vijay AK, Dumpati S, Masoudi S, Willcox M. Diurnal variation of tear and meibum lipids in healthy subjects. Ophthalmic Physiol Opt. Published May 27, 2026. doi:10.1007/s44402-026-00112-5

2. Perez VL, Chen W, Craig JP, Dogru M, Jones L, Stapleton F, et al. TFOS DEWS III: executive summary. Am J Ophthalmol. 2026;282:135-145. doi:10.1016/j.ajo.2025.09.035

3. Bron AJ, Tiffany JM, Gouveia SM, Yokoi N, Voon LW. Functional aspects of the tear film lipid layer. Exp Eye Res. 2004;78:347-360. doi:10.1016/j.exer.2003.09.019

4. Chhadva P, Goldhardt R, Galor A. Meibomian gland disease: the role of gland dysfunction in dry eye disease. Ophthalmology. 2017;124:S20-S26. doi:10.1016/j.ophtha.2017.05.031

5. Wolffsohn JS, Lingham G, Downie LE, et al. TFOS Lifestyle: impact of the digital environment on the ocular surface. Ocul Surf. 2023;28:213-252. doi:10.1016/j.jtos.2023.04.004