Short-Term Changes in Tear Lipid Layer Thickness After Instillation of Lipid Containing Eye Drops

Lipid-containing eye drops is increasingly popular in eye clinics to treat dry eye. Tear lipid layer thickness (LLT) changes after instillation of lipid eye drops have not been characterized. We aim to evaluate these changes of LLT using a noninvasive interferometry-based method.

This prospective clinical study was conducted on staff and patients from Singapore National Eye Centre with ad hoc recruitment. Noninvasive tear break up time was measured using the Keratographer 5M. LLTs were measured using a tear interferometer machine before and at 1, 5, and 15 minutes after instillation of lipid-containing drops, either Cationorm unidose or Artelac Lipids. Fluorescein clearance (tear clearance rate) and Schirmer tests were conducted. The tear clearance rate of fluorescein dye was based on the visual examination of the color of a Schirmer strip after 5 minutes, compared against color standards.

This study included a total of 84 participants aged ≥21 years. Many were female (92.8%) and Chinese (89.2%). A tear clearance rate of 1/16 was most common (35.7%), whereas 1/128 and 1/32 were uncommon (3.57% each). Schirmer results were 6.5 ± 8.1 mm, and noninvasive tear break up times were 8.12 ± 6.25 mm. Participants with baseline LLT <60 nm had greater changes in LLT after Cationorm instillation, compared with those with an LLT of >60 nm. LLT changes over 15 minutes were not associated with tear clearance rate. Similar results were obtained when using Artelac Lipids.

Our results showed that participants' initial LLT affected their responsiveness to lipid-containing eye drops more than other factors.

Doctors may choose to measure the baseline LLT of patients before deciding whether to prescribe lipid eye drops to patients.