Abstract
Purpose:
To evaluate the thickness of the lipid layer of the tear film in healthy subjects with a new interferometry device (Lipiview®) before and after instillation of various commercially available tear substitutes with lipid composition.
Methods:
Ten healthy subjects (20 eyes) were included in a randomized, double-masked study to participate in a three-day visit evaluation. Before, subjects completed a dry eye questionnaire (ocular surface disease index-OSDI-) to evaluate symptoms of dry eye. Only normal individuals, defined as a Schirmer test result without anaesthesia above 10 mm/5min and Tear Break Up Time (TBUT) above 7s were included. A semiautomated interferometre (Lipiview® system), was used to measure the precorneal tear lipid layer thickness followed by measurement of the non-invasive break up time (NITBUT) with Oculus Keratograph® 5M. Then one of three lipid emulsion eye drops/spray (which main components contained were lipid carbomer, rizin oil and lecithin soy respectively) was applied while the fellow eye received sodium hyaluronate, sodium carboxymethylcellulose or saline spray solution for negative control. In randomised sequence and after one week of wash-out between measurements, the 2nd and again one week later a 3rd emulsion was also studied. Measurements were performed at baseline and at 15, 30, 60, and 120 minutes after instillation of the drops or application of the spray.
Results:
Tear lipid layer thickness significantly increased in all subjects after lipid emulsion instillation. The emulsion with lipid carbomer showed a significant increase at 15 and 30 time points from baseline (p=0.012 and p=0.01). The emulsion with rizin oil also significantly raised lipid layer thickness for 15 and 30 minutes (p=0.009 and p=0.002) and showed good correlation with NIBUT (p=0.001), as this parameter also increased from baseline at the same time points. Lecithin soy spray significantly increased the lipid concentration at 30 minutes only (p=0.006).
Conclusions:
Lipid emulsion eye drops significantly increase the lipid layer thickness of the tear film measured with Lipiview® in healthy subjects. This effect lasts for only 30 minutes after instillation. The lipid layer thickness correlated well with the NIBUT.
Keywords: 486 cornea: tears/tear film/dry eye