Presentation Transcript
TEARS: TEARS Protective layer
Watery liquid-Bathes/Nourishes
Three layers: Lipid, Aqueous and Mucin
Tear – secreted by glands around the eyelid
TEAR PRODUCTION: TEAR PRODUCTION Lipid layer
– Meibomian glands &
Glands of Zeis
Aqueous layer
– Lacrimal glands,
Glands of Krause &
Wolfring
Mucin Layer
Goblet cells
PHYSICAL CHARACTERISTICS OF TEAR FILM: PHYSICAL CHARACTERISTICS OF TEAR FILM Surface tension :40-50 dynes/cm2
pH :6.9 -7.4
Osmolarity :290-310 mOsm/l
Viscosity :1.9-2 centipoises
FUNCTIONS OF TEAR FILM : FUNCTIONS OF TEAR FILM Lubricates and moistens eye surface
Provides nutrients & oxygen to cornea
Washes away foreign bodies
Protects against bacteria and viruses (with help of enzyme Lysozyme)
COMPOSITION OF TEAR FILM: COMPOSITION OF TEAR FILM Lipid layer
Proteins (albumin, globulin)
Lysozyme (antibacterial)
Aqueous layer
Nutrients (minerals,Vitamins, electrolytes)
Mucin layer
Glycoproteins make the corneal
surface more hydrophilic
FUNCTIONS OF THE TEAR FILM LAYERS: FUNCTIONS OF THE TEAR FILM LAYERS Lipid layer
Prevents evaporation of aqueous layer.
Aqueous layer
Nourishes and moisturizes the cornea and sclera.
Protects against micro-organisms
Mucin layer
Helps in the even spreading of the tear film over the ocular surface
TEAR SECRETION : TEAR SECRETION Two types of secretors :- basic and reflex
Basic secretors
Supply tears at constant rate – gland of Krause and wolfring
Reflex secretors
Supply tears when there is a stimulus like foreign body, emotions, bright light.
BLINKING: BLINKING Provides regular rewetting
Ensures normal tear film function
Tear Break Up Time (TBUT) – 10 seconds
Compromised blinking – leads to SSS (Screen Stare Syndrome)
TEAR DRAINAGE: TEAR DRAINAGE PUNCTA
CANALICULI
LACRIMAL SAC
NASO LACRIMAL DUCT
EVAPORATION