Transcript Functions of tear film

Functions of tear film
Smooth optical surface at the air-eye interface
Removal of debrise in eye surface
To protect the ocular surface
To supply oxygen, growth factors and other
compounds to the corneal epithelium
Contain antimicrobial agents
Lubricates the cornea-eyelid interface
Tearfilm is a trilaminar structure
 Lipid layer
a: retard evaporation
b: optical properties
c: prevent tear overflow
 Aqueaus layer
a: consist of electrolytes, water and protein
b: secreted by main and accessory glands
 Mucin layer
a: facilitated distribution of tear film
b: stabilizing the tear film
c: lubricated globe-eyelid surface
 Tear secretion has two components
1- basic secretors
2- reflex secretors
 Eyelidmovement is important in tear film renewal ,
distribution, turnover and drainage
 Tear dry function
1- change in the amount of tear film
2- change in the composition of tear film
3- uneven dispersion of the tear film because of corneal-surface
irregularities
4- ineffective distribution of tear film caused by eyelid-globe
incongruity
Tear dysfunction management
 Creating a more regular corneal or conjunctival contour
 Facilitating eyelid-globe congruitg especially managing
of entropion and ectropion
 Decreasing evaporation of tear ( room temperature or
humidity)
 Topical tear substitutes
 Reduction of tear drainage (punctal occlusion)
 Dressing sunglasses