Do diurnal and gender-related variations affect tear film? A pilot study

Background: The tear film is a dynamic structure influenced by physiological, environmental, and biological factors. Since the ocular surface is highly sensitive to the gonadal hormones, it is worthwhile to investigate whether various parameters of the tear film show measurable variation, particularly in healthy young adults. This pilot study investigated temporal and sex-related variations in tear film parameters in healthy young adults.

Methods: A prospective, observational pilot study was conducted among university students. Of the 35 individuals selected, 15 healthy subjects (mean age 19.93 ± 1.49 years) met the eligibility criteria. Tear film evaluations were conducted on three days per week for four consecutive weeks at three fixed intervals each day—morning (9:00–10:00 a.m.), afternoon (1:00–2:00 p.m.), and evening (6:00–7:00 p.m.). Qualitative assessment included Non-Invasive Tear Break-Up Time (NIBUT) and Tear Meniscus Height (TMH). Quantitative assessment was performed using Schirmer’s II Test. Data were analysed to identify diurnal changes, weekly trends, and gender correlations on tear film stability and quantity. Statistical significance was set at 5% level of significance with 95% confidence intervals.

Results: Though a few parameters showed minor statistical differences, the tear film measures were largely stable when checked for interocular, diurnal, or gender related variations. No significant weekly variations were observed in the female subjects.

Conclusion: Tear-film parameters demonstrated parameter-specific and inconsistent temporal variation rather than a uniform diurnal pattern in healthy young adults. Sex-related differences were also observed, with higher tear secretion, tear-film stability, and tear meniscus height among males in this pilot cohort. These preliminary findings highlight the potential importance of measurement timing and biological sex when interpreting tear-film assessments.

Keywords: Tear film stability, NIBUT, Schirmer’s test, Tear prism height, Diurnal variation, Gender differences, Gonadal hormones

Sudha Prasad is an Assistant Professor of Optometry at Brainware University, India, holding a Master’s degree in Optometry and having completed her clinical internship at the prestigious L V Prasad Eye Institute (LVPEI), Hyderabad. Her clinical and research interests include ocular surface health, tear-film physiology, dry eye, binocular vision, refractive error, and visual function. She has published research articles and co-authored book chapters in the field of optometry and vision science. She is actively engaged in teaching, clinical research, student mentorship, curriculum development, and academic coordination, with a strong commitment to advancing evidence-based optometry education, research, and clinical practice.