Lipid layer thickness of tear film and its association with clinical characteristics in different types of dry eye patients

Abstract

Objective To investigate tear film lipid layer thickness (LLT) and its association with clinical symptom and sign in different types of dry eye patients. Methods A serial case-observational study was carried out.Three hundred and six eyes of 306 dry eye patients were included in Beijing Tongren Hospital from April to August 2016.Ocular surface disease index (OSDI) questionnaire, eyelid slit lamp examination, the measurement of tear film lipid thickness (LLT), tear film break-up time (TBUT), Schirmer Ⅰtest (SⅠt) and the infrared meibomian photography were performed on the patients.The 157 patients with OSDI >12 and eyelid score ≥2 served as the MGD group; 53 patients with OSDI >12 and SⅠt value﹤5 mm/5 minutes served as ADDE group; 96 patients with OSDI>12, eyelid score ≥2 and SⅠt value﹤5 mm/5 minutes served as MGD/ADDE group.Tear film LLT was detected with LipiView® ocular surface interferometer and the association of LLT with clinical characteristics of the patients was analyzed.This study protocol was approved by Ethic Committee of Beijing Tongren Hospital and written informed consent was obtained from each patient prior to any relative medical examination. Results Tear film LLT of the participants was normally distributed with the average was (60.41±18.57)nm.LLT in the MGD group, ADDE group, MGD/ADDE group were (57.04±18.26), (63.52±18.44) and (60.56±18.71)nm, respectively, with a significant difference among the three groups (F=2.347, P=0.035), and the LLT value was significantly lower in the MGD group than that in the ADDE group (t=2.077, P=0.039). The LLT value showed negative correlations with the severity of dry eye symptom, SⅠt and meibomian gland loss rate (r=-0.201, P=0.003; r=-0.146, P=0.005; r=-0.156, P=0.046). OSDI score was significantly correlated with LLT only in the MGD group (r=-0.285, P=0.000). No significant correlation was seen between LLT and SⅠt in all the groups (all at P>0.05). In the MGD/ADDE group and MGD group, the correlation between LLT and meibomian gland loss rate was significantly greater than the overall correlation (r=-0.335, -0.248, -0.156). The dry eye symptoms in OSDI questionnaire like foreign body sensation, eye pain, discomfort when watching TV or computer showed significant correlations with LLT (r=-0.243, -0.205, -0.223, -0.258, all at P<0.05). Conclusions The tear LLT is appeared to be varied in different types of dry eye.The LLT is thinner in the dry eyes with MGD and thicker in the dry eyes with ADDE.There are association between tear LLT and foreign body sensation, eye pain, discomfort when watching TV or computer. Key words: Dry eye; Tear film; Lipid layer thickness; Ocular surface disease index; Tear film break-up time; Schirmer I test; Case-observational study