Nanoscale phase dynamics of the normal tear film

The three layers of the tear film. The outermost hydrophobic lipid layer is approximately 100 nm thick; the middle aqueous layer comprises over 90% of the tear film; and the inner hydrophilic mucin layer is embedded at the corneal epithelium.

Aqueous qdots applied to the ocular surface. (A) qdots being applied to the surface; (B) 4 seconds after application the qdots have spread from the local application point; (C) 17 seconds after application just before blink. (D) Blink showing surface of eyelid; (E) 0.02 seconds after the blink, note that few qdots remain on the surface (arrows). (F) After the second blink qdots have all but disappeared from the surface; (G) the qdots accumulated in the aqueous lake (arrow) between the lower lid and the ocular surface. LM, lower lid margin. (H) The eyelid has been everted to reveal the lower punctum, which shows the lumen filled with qdots (arrow). The aqueous lake between the lower eyelid and the ocular surface can also be seen to be strongly stained. Scale = 2 mm.

Lipophilic qdots after placing them on the lower lid margin. (A) Just after application the qdots spread as rafts all over the ocular surface (arrows), and there was no staining of the eyelid margin. (B) After a blink the qdots could be seen dispersed as diffuse areas (arrows) in the outer layer of the tear film. (C) qdots jetting from a meibomian gland orifice. (D) Blobs of qdots within the aqueous lake beneath the superficial lipid layer. The lower lid margin (LM) is strongly stained after the first blink. (E) No fluorescence is seen inside the punctum (arrow). (F) The eyelashes are stained with the lipophilic qdots (long white arrow), and there is some staining of the periocular skin (short white arrow); the ocular side of the eyelid is unstained (black arrow). (G) The lipophilic barrier, a distinct stained line on the eyelid margin (white arrow), seen after a few lipophilic qdots were placed at the base of an eyelash; the meibomian gland orifices (black arrows) can be seen on the ocular side of this line. OS, ocular surface. Scale = 2 mm.