Competing/conflicts of interest: No stated conflict of interest.
Fluids of the ocular surface: concepts, functions and physics
Article first published online: 21 MAR 2012
© 2012 The Author. Clinical and Experimental Ophthalmology © 2012 Royal Australian and New Zealand College of Ophthalmologists
Clinical & Experimental Ophthalmology
Volume 40, Issue 6, pages 634–643, August 2012
How to Cite
Cher, I. (2012), Fluids of the ocular surface: concepts, functions and physics. Clinical & Experimental Ophthalmology, 40: 634–643. doi: 10.1111/j.1442-9071.2012.02758.x
Funding sources: No stated funding sources.
- Issue published online: 13 AUG 2012
- Article first published online: 21 MAR 2012
- Accepted manuscript online: 2 FEB 2012 11:54AM EST
- Received 26 June 2011; accepted 10 December 2011.
- black lines;
- lipid sealant;
- ocular surface system (OSS)
General adoption of the ocular surface (OS) concept has advanced the therapy of the external eye. Fresh physical findings have prompted new concepts; examples taken from each section of the text are: (i) ever-present lipid sealant bridges the palpebral fissure capping the three-dimensional ‘OS’ sac. The muco-aqueous pool (MAP) is thus enclosed, secluded from atmosphere, evaporation mitigated. Hence, the OS is conceptually, a compartment. The term ‘dacruon’ (otherwise ‘tear film’) has been coined for the combined fluids of the OS, viz. lipid film and MAP. (ii) Investigative techniques of physics yield data on (say) surface tension and viscosity, and on functions such as anchorage of dacruon base to the varied mucosae of the OS, lubrication, renovation of intermarginal fluid layers as the eye opens after each blink, and refinement of optics and vision by the fluids attached to the cornea. (iii) Physical events in the opening eye produce the unique ‘black line’ phenomenon in which capillary force induces subsurface flows into thirsty menisci, bringing about parameniscal dark grooves, pupil-ward of each meniscus. Attenuation of fluorescein in the shallowed fluid gaps behind each groove makes the dye appear unilluminated (‘black lines’) relative to adjacent full-thickness MAP fluid glowing under cobalt-blue illumination. Isolated from cornea by grooves and gaps, the meniscal fluid cannot pass freely over the cornea. It therefore streams through the menisci to nasolacrimal outflow.