ABSTRACT
Purpose: To compare the function and morphology of the meibomian glands and the ocular surface of individuals from highland and lowland. Methods: This was a randomized controlled trial. The study was performed with 104 individuals (51 individuals from the highland and 53 individuals from the lowland). Detailed eye examinations comprising tear meniscus height, lipid layer grading, non?invasive Keratograph tear breakup time (NIKBUT), and scoring of the meibomian glands from the upper and lower eyelids of the individuals were performed by Keratograph 5M (OCULUS, Wetzlar, Germany). Symptoms related to dry eye disease were assessed using the Ocular Surface Disease Index (OSDI). Results: In the highland group, tear meniscus height was lower (P = 0.024), lipid layer grade, as well as all the meiboscores were higher (P < 0.05) than that in the lowland group. The OSDI (P = 0.018) and the percentage of dry eye disease were also higher as compared to that of the lowland group (P = 0.032). The first NIKBUT and average NIKBUT did not differ significantly between groups. The frequency of plugged meibomian gland orifices was greater in the lowland group compared to the highland group (P = 0.036). Conclusion: It was observed that dry eye disease was more common in the highland group. The morphological changes of meibomian gland dropout were significant in highlanders as demonstrated objectively with Keratograph 5M. Our study may raise a concern for environmental influences on ocular surface changes