Week 2: Tear Film and Ocular Surface

Question 1

What is the function of the lipid layer?

Answer 1

Prevents evaporation

Question 2

What secretes the lipid layer of the tear film?

Answer 2

The Meibomian glands and Zeiss glands

Question 3

What is the size of the Aqueous Layer?

Answer 3

7 microns

Question 4

What secretes the Aqueous Layer of the tear film?

Answer 4

Primary Lacrimal gland and the Krause and wolfring accessory glands

Question 5

What is the function of the mucin layer of the tear film?

Answer 5

Provides viscostiy and stability during the blink cycle. Makes the surface of the corneal epithelium hydrophilic

Question 6

What secretes the Mucin layer of the tear film?

Answer 6

Goblet cells and conjunctival epithelium

Question 7

What are the functions of the tear film?

Answer 7

Optical –uniform interface between air and cornea

Lubricant –allows for smooth movement of lids over globe

Bactericidal –Contains immuno-defense mechanisms to
prevent ocular infection

Nutritional –Supplies cornea with oxygen, glucose, amino acids,
vitamins

Waste removal –removes by-products of metabolism from
cornea (CO2)

Question 8

What are the steps of the blink function?

Answer 8

1. Inhibition or relaxation ofLevator
2. Contraction of orbicularis bringing the upper and lower lid into
   contact. This moves the tears toward the puncta.
3. Riolan’smuscles contracts and release Meibum
4. Reopening phase involves activation of Levator muscle

Question 9

What is a healthy blink rate?

Answer 9

12x/ min or every 3 - 7 secs

Question 10

What are some components that can be found in the tear film?

Answer 10

• Electrolytes (Na, K, Cl, Ca)
  
  • Proteins (Lysozymes, Fe, Lactoferrin, Lipocalin, Albumin, EGF)
  • Cytokines
  • Mucin 1, Mucin 4, Mucin 5AC
  • Latent Proteases
  • Immunoglobulin A (IGA) - prevents bacterial infection
  • Trefoil factor
  • Galectin - 3
    Lactoferrin

Question 11

What is the tear production rate?

Answer 11

1 microlitre / min

1.5mL/day

Question 12

What aspects of DED do we examine clinically?

Answer 12

Tear drainage, tears spread and coverage, tear quality, tear production

Question 13

What do we look at when examing tear production?

Answer 13

Blink rate
efficiency of blink
volume of tear production

Question 14

What are the tests for measuring tear production?

Answer 14

Schirmer Test

Red phenol thread (no longer available)

tear prism height (meniscus height)

Question 15

What are we looking at when we exam tear quality?

Answer 15

Tear osmolarity - using TearLab
Tear structure - 
 - are the tears staying on the eye?
- are they evaporating?
- are they patchy in some places of the eye?

Question 16

What do we examine when we look at Tear and coverage?

Answer 16

Tear break up time (TBUT)

with slit lamp and with fluorescein

Question 17

Why do we use fluroscein staining?

Answer 17

• it water soluble
• no sting
• will show you any TBUT and good for corneal epithelium assessment

Question 18

Why do we use Lissamine Green Staining?

Answer 18

It has an affinity for dead or devitalised cells (doesnt stain healthy epithelial cells)
good for lid wiper epitheliopathy
good for conjunctiva assessment

Question 19

Why did we use Rose Bengal Stain?

Answer 19

It was good for conjunctival staining.
Drawn to dead or degenerate cells.
But it stings the patient

Question 20

Compare the methods for measuring Tear Volume

Answer 20

Tear Prism Height: Previous research has found strong correlation of tear prism height with cotton

red thread test and tear break up time (TBUT) and scores of ocular staining1

SchirmersTest (note reflex vs non reflex tearing)

Red Phenol Thread test (no longer available?)

Question 21

Describe in detail Tear Break up time.

Answer 21

Tear break up occurs when lipid, which is
hydrophobic migrates down to the mucus
layer  and compromises the hydrophilic
nature of the mucin covered epithelial
surface.

Measures the structural integrity of the tear film
the time elapsed between normal blink and evaporation of tears.

Tears recede from this area of poor wettability
and a dry spot forms.

These regions highlight areas of the surface
vulnerable to epitheliopathy

Normal TBUT is more than 10s

Question 22

What is Lip Wiper Epitheliopathy?

Answer 22

The clinical condition observed as vital staining of the upper and lower lid margin regions that are in contact with the globe or a contact lens. It is believed to result from an increase in friction between the palpebral lid and the opposing bulbar conjunctiva, cornea, or contact lens
Symptomatic (80%) dry eye and contact lens patients present
significant staining of the lid wiper, vs only 13% of asymptomatic
patients.

Question 23

How do you describe a lesion?

Answer 23

1. Location (Nasal, temporal, superior, inferior) - And right eye or left eye!
2. Tissue (cornea, conjunctiva, tarsus, limbus, iris etc)
3. Layer (epithelium, stroma, endothelium)
4. Extent (punctate, diffuse, coalescent, physical size mm x mm)
5. Type (infiltrate, abrasion, nodule etc etc)
6. Extra (pigment, vascularised etc)

Question 24

What is to be assessed during a meiboimain gland assessement?

Answer 24

Assess number and quality of glands
Capping of glands
Discharge of glands

Question 25

What is the purpose of conjunctival folds assessment?

Answer 25

Folds may represent the first stages of conjuctivochalais

associated with decreased mucin production

Question 26

In what order should diagnostic tests be performed?

Answer 26

• Case history validated DED questionnaire
• NIBUT
• Tear Osmolarity
• Tear quantity and volume
• Anterior segment evaluation
• Fluorescein tear break-up time
• Integrity of cornea and conjunctiva
• Meibomian gland expression and assessment

Question 27

What is some ways to manage Aqueous DED?

Answer 27

Replace tears with eye drops
Preserve Tears with punctal plugs
Stimulate tears with secretagogues

Question 28

What is some ways to manage Evaporative DED?

Answer 28

Depends on the cause

• blepharitis - lid wash
• meibomian glands - warm compress, lipiflow, bead masks, MBG expression, golf spud lid margin debridement, Intense pulse light therapy, oral antibiotic

Question 29

What are the main treatments for inflammation

Answer 29

Topical Steroids

Topical cyclosporine