Tear Evaporation Rates and Lipid Layer Status in Non–Sjögren Syndrome Aqueous Tear Deficiency Dry Eye Patients

Abstract

Abstract: : Purpose: To investigate tear evaporation rates and tear lipid layer status in non–Sjögren Syndrome aqueous tear deficiency dry eye patients (non–SS ATD). Methods:21 eyes of 12 non–SS ATD dry eye patients (3 males and 9 females; mean age: 51.9±17.2 years) were participated in this study. Tear evaporation rates were measured using our recently reported new ventilated chamber system. Tear lipid layer condition was evaluated using DR–1 tear interference camera and Yokoi dry eye severity grading was applied (Kowa, Nagoya, Japan). To compare the tear status between severe and mild cases, non–SS ATD subjects were subdivided into 2 groups according to the presence of corneal fluorescein staining, as the positive fluorescein staining group (n=8 eyes) and negative fluorescein staining group (n=13 eyes). Our previous data of normal subjects measured by the same instrument set–up (4.1 ± 1.4 x10^–7g/cm²sec) were used for reference comparison. Results: The mean tear evaporation rates in non–SS ATD was 2.9 ± 1.8 x10^–7g/cm²sec, which was significantly lower than that of normal subjects (P = 0.004). Tear evaporatin rates of positive and negative fluorescein staining groups were 1.5 ± 0.8, and 3.7 ± 1.7x10^–7g/cm²sec (P = 0.0009). DR–1 gradings were 3.8 ± 1.0 and 2.3 ± 0.5, respectively (P = 0.02). Conclusions:Tear evaporation rates in non–SS ATD was low, especially in positive fluorescein staining group. Decreased evaporation rates in positive fluorescein staining group could be explained with abnormally thick lipid layer thickness (120∼220 nm) observed by DR–1 interferometry. Normal evaporation rates in negative fluorescin staining group also could be explained by the balance of thin surface lipid layer (30∼40 nm) and decreased tear secretion. Observation of tear lipid layer using DR–1 was useful to predict evaporative tear loss from ocular surface.

Keywords: cornea: tears/tear film/dry eye • cornea: clinical science • cornea: epithelium