Anatomy/Tear Film Flashcards
(32 cards)
Eyelid fuctions
- Protects the globe
- Distributes tears over anterior
- Limits light entering the eye
Eyelid anatomy
Opening formed: palpebral fissure
Junction of upper/lower lids: canthi
Opening (5mm) from inner canthus: puncta
Punctum
Small opening in lids where tears drain
Cilia
Eyelashes
(Low reflexes, 100-150, 3-5mo life span)
More on upper lid than lower
Conjunctiva
Thin vascular mucous membrane, lining upper and lower lids.
Conjunctiva functions
- Defends and repairs cornea
- Blood vessel provide nutrients and antibodies to the tear film
Tarsas plate
Connective tissue covering the orbicularis muscle (closes lids during forced closure)
Canaliculi
Small drainage ducts that connect to the lacrimal sac
Nasolacrimal duct
Carries tears from the eye and drains into the nasal passages
Lacrimal sac
Located in the medical portion of the eye
Collects tears for drainage into the nasolacrimal duct
Lacrimal system
Located on upper temporal side of orbit
Secretes part of tear film that keeps conjunctiva and cornea moist
Contains enzyme lysozyme
(8-12 excretory ducts)
Lacrimal draining steps
- Punctum
- Canaliculi
- Lacrimal sac
- Nasolacrimal duct
Layers of tear film: Tear layer
Consists of lacrimal gland and accessory glands of Krause and Wolfring.
- Responsible for oxygen up take to maintain corneal metabolism
- K & W located on upper lid inside surface
*Lacrimal gland is resp. for aqueous part of the tear film
Layers of tear film: Oily layer
Dervived from meiboman glands and sebaceous glands of Zeiss and Moll.
Functions ot lubricate tear film, prevents evaporation and spillage of tears.
Zeiss
Small sebaceous gland that secretes oily substance and deposits into lashes
Moll
Modified sweat glands, secretes lipids adding to oily layer
Layers of tear film: Mucoid layer
Produced by the goblet cells of conjunctiva
Goblet cells
Make cornea wettable by providing a surface over which tears spread easily.
Attaches to cornea by microvilla that anchor film to cornea
Traps debris and deposits into nasal canthus.
Tear film jobs
- Antibacterial
- Mechanical flushing of debris
- Smooth refracting surface
- Keeps eye moist
- Corneal metabolism
Tear facts
Ph: 7.3
Consists of 98.2% water
No tears are produced at night
50% of tears are lost through evaporation
Dacryocystitis
Inflammation of the lacrimal sec
Dacryoadentis
Inflammation of the lacrimal gland
Epiphora
Constant tearing due to blocked drainage passages or excessive production
Schirmer’s tear test
Tests for adequate tear FUNCTION/PRODUCTION
Test 1: With anesthetic, tests basal and reflex
Test 2: Without anesthetic, tests reflex tearing
