Lipid layer thickness decrease due to meibomian gland dysfunction leads to tear film instability and reflex tear secretion

PURPOSE: To determine the clinical effects of ocular surface and Meibomian gland parameters on tear film stability among individuals with Meibomian gland dysfunction (MGD), those with aqueous deficient dry eye (ADDE), individuals with both conditions and normal controls. METHODS: Patients were divided into four groups: normal controls, patients with ADDE, patients with MGD, and patients who fulfilled diagnostic criteria for ADDE and MGD (Mixed Group). Data for ocular symptom score, lid margin abnormality, ocular staining, tear break-up time, meiboscore, and lipid layer thickness (LLT) measured by a Lipiview interferometer, Schirmer test, and MGD severity score were collected. RESULTS: A total of 109 patients (109 eyes) were evaluated. In patients with MGD, LLT was significantly lower than the ADDE patients. However, the Schirmer test value was the highest in the MGD group. The LLT negatively correlated with meiboscore and MGD severity score in the MGD group. Significant correlation between Schirmer test value and meiboscore was definite in the MGD group. CONCLUSIONS: Tear fluid secretion is more increased and lipid layer thickness is more decreased in MGD patients than in ADDE patients. Decreased lipid layer thickness caused by MGD-related tear film instability may stimulate reflex tear secretion. The obstructive MGD is more prevalent than hypersecretary MGD. KEY MESSAGES: The tear film stability is affected by Mebomian gland dysfunction (MGD). The measurement of the tear film parameters including lipid layer thickness suggests that the obstructive MGD is more prevalent than hypersecretary MGD and the aqueous layer compensates the decreased lipid layer caused by MGD.