Anatomy/Tear Film

Question 1

Eyelid fuctions

Answer 1

• Protects the globe
• Distributes tears over anterior
• Limits light entering the eye

Question 2

Eyelid anatomy

Answer 2

Opening formed: palpebral fissure
Junction of upper/lower lids: canthi
Opening (5mm) from inner canthus: puncta

Question 3

Punctum

Answer 3

Small opening in lids where tears drain

Question 4

Cilia

Answer 4

Eyelashes
(Low reflexes, 100-150, 3-5mo life span)
More on upper lid than lower

Question 5

Conjunctiva

Answer 5

Thin vascular mucous membrane, lining upper and lower lids.

Question 6

Conjunctiva functions

Answer 6

• Defends and repairs cornea
• Blood vessel provide nutrients and antibodies to the tear film

Question 7

Tarsas plate

Answer 7

Connective tissue covering the orbicularis muscle (closes lids during forced closure)

Question 8

Canaliculi

Answer 8

Small drainage ducts that connect to the lacrimal sac

Question 9

Nasolacrimal duct

Answer 9

Carries tears from the eye and drains into the nasal passages

Question 10

Lacrimal sac

Answer 10

Located in the medical portion of the eye
Collects tears for drainage into the nasolacrimal duct

Question 11

Lacrimal system

Answer 11

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)

Question 12

Lacrimal draining steps

Answer 12

1. Punctum
2. Canaliculi
3. Lacrimal sac
4. Nasolacrimal duct

Question 13

Layers of tear film: Tear layer

Answer 13

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

Question 14

Layers of tear film: Oily layer

Answer 14

Dervived from meiboman glands and sebaceous glands of Zeiss and Moll.
Functions ot lubricate tear film, prevents evaporation and spillage of tears.

Question 15

Zeiss

Answer 15

Small sebaceous gland that secretes oily substance and deposits into lashes

Question 16

Moll

Answer 16

Modified sweat glands, secretes lipids adding to oily layer

Question 17

Layers of tear film: Mucoid layer

Answer 17

Produced by the goblet cells of conjunctiva

Question 18

Goblet cells

Answer 18

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.

Question 19

Tear film jobs

Answer 19

1. Antibacterial
2. Mechanical flushing of debris
3. Smooth refracting surface
4. Keeps eye moist
5. Corneal metabolism

Question 20

Tear facts

Answer 20

Ph: 7.3
Consists of 98.2% water
No tears are produced at night
50% of tears are lost through evaporation

Question 21

Dacryocystitis

Answer 21

Inflammation of the lacrimal sec

Question 22

Dacryoadentis

Answer 22

Inflammation of the lacrimal gland

Question 23

Epiphora

Answer 23

Constant tearing due to blocked drainage passages or excessive production

Question 24

Schirmer’s tear test

Answer 24

Tests for adequate tear FUNCTION/PRODUCTION

Test 1: With anesthetic, tests basal and reflex
Test 2: Without anesthetic, tests reflex tearing

Question 25

How is the cornea bound?

Answer 25

Anteriorly by tear film
Posteriorly by the aqueous
Laterally by the conjunctiva/sclera

Question 26

Cornea facts

Answer 26

75% of the cornea is for refraction
N= 1.376
Anterior diameter: 11.5mm high, 11.2mm wide
Avg. thickness: 0.50mm
Radius of curvature: Ant. 7.8mm, post. 6.5mm

Question 27

5 Layers of the cornea

Answer 27

1. Epithelium
2. Bowman’s membrane
3. Stroma
4. Descemet’s membrane
5. Endothelium

Question 28

Epithelium

Answer 28

First line of defense for cornea
Regenerates
Helps maintain transparency
Makes up 10% of corneal thickness

Question 29

Bowmans

Answer 29

Filled with collagen and fibers
Resistance to infections
Does NOT regenerate

Question 30

Stroma

Answer 30

90% of cornea
Filled with collagen
Does NOT regenerate

Question 31

Desecements

Answer 31

Inner layer of basement membrane
Important for health of endothelium

Question 32

Endothelium

Answer 32

Thin
Removes excess moisture
Helps with transparency