Seasonal Variation in Tear Secretion and Tear-Film Stability among Adults in Enugu, Nigeria: A Longitudinal Study

Abstract

Aim: To investigate the variation in tear-film secretion and function between rainy and dry seasons among healthy adults in Enugu, Nigeria. Methods: This was a population-based, longitudinal study involving a cohort of 31 healthy adult Nigerians residing in Enugu in 2018. The objective tests for tear secretion (Schimer’s test) and function (tearfilm break-up time, TBUT) were conducted on the 62 eyes of the participants in January and July, the peaks of dry (D) and rainy (R) seasons, after obtaining their socio-demographic information. Their palpebral fissure height (PFH) and length, (PFL) were also obtained. Data was analysed using SPSS version 21. The level of significance was at p< 0.05. Results: The participants comprised of more females, 20 (64.5%) than males, with a mean age of 33.7 ± 9.6 SD years. They were mainly civil servants with tertiary education.The mean TBUT -R was 30.0 ±18.3 seconds and D, 15.6 ± 9.5. The mean Schirmer’s test-R was 25.2 ± 10.1 mm and D, 22.1 ± 11.2 mm. There was significant difference between these means in rainy and dry seasons. (p =0.000 TBUT, p = 0.04 Schirmer’s test). When TBUT and Schirmer’s test in both seasons were correlated with PFH and PFL, only TBUT -R and PFH showed a significantly positive correlation (r = 0.54, p= 0.002). Conclusion: A significant seasonal variation in tear-film secretion and function exists among adults in Enugu. The higher the PFH, the less the break-up of the tear-film during rainy season. These findings have great implications in the management of dry eyes. The use of therapeutic lubricant gels to prolong the TBUT time in dry seasons may therefore be preferred.