Abstract
Purpose :
Meibomian lipids (ML) flowing outwards on the lid margin has been proposed as a barrier preventing skin lipids (SL) entering the eye and disrupting the stability of the tear film (TF). This was examined in humans using in an in vivo experimental approach.
Methods :
The side of the nose was wiped lightly with chloroform cleaned threads to load them with skin swab substance (SSS). Else they were loaded with control lipids representative of those found on skin or acetic acid as a control for low pH. The corneal surface, eyelid margin, eyelash base, or the lacrimal lake were touched with a cleaned (control) or loaded thread in 3 healthy volunteers. Effects on the tear film were visualised using fluorescein or a new device, TearView (TV), that visualises TF formation and stability in real time.
Results :
Both TV and fluorescein showed that minimal amounts of SSS applied to the cornea, eyelid margin or lacrimal lake but not the eyelash base spread and destroyed the TF’s integrity, which was not restored for several blinks. The SSS caused pain, and staining of the corneal surface. TV showed that SSS triggered ML secretion that displaced the SSS presumably giving protection. Acetic acid (5% aqueous), emulating skin pH, locally destroyed the TF but did not spread from the site of touch. It caused corneal staining and the TF recovered with one blink. Neutral control lipids did not cause any discomfort and did not destroy the TF but instead smeared across the TF when blinking. By contrast, free fatty acids, typical components of the skin lipidome, had similar effects to the SSS.
Conclusions :
This is the first study showing the effects SSS contamination of the human ocular surface. SSS caused TF disruption, pain, fluorescein staining of the corneal surface, and triggered meibomian gland activity, presumably as a physiological response to increase protection against SL.TF disruption is probably due to fatty acids and low pH. This supports the proposed barrier function of meibum on the eyelid margin. This barrier would be compromised by diminished ML secretion, or excess of SL secretion which would overwhelm the lid margin barrier. Therefore, SL contamination of the ocular surface might be a common factor for the cause of dry eye in various types of blepharitis, ocular rosacea and meibomian gland dysfunction.
This abstract was presented at the 2023 ARVO Annual Meeting, held in New Orleans, LA, April 23-27, 2023.