Week 2: Tear Film and Ocular Surface Flashcards
What is the function of the lipid layer?
Prevents evaporation
What secretes the lipid layer of the tear film?
The Meibomian glands and Zeiss glands
What is the size of the Aqueous Layer?
7 microns
What secretes the Aqueous Layer of the tear film?
Primary Lacrimal gland and the Krause and wolfring accessory glands
What is the function of the mucin layer of the tear film?
Provides viscostiy and stability during the blink cycle. Makes the surface of the corneal epithelium hydrophilic
What secretes the Mucin layer of the tear film?
Goblet cells and conjunctival epithelium
What are the functions of the tear film?
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)
What are the steps of the blink function?
- Inhibition or relaxation ofLevator
- Contraction of orbicularis bringing the upper and lower lid into
contact. This moves the tears toward the puncta. - Riolan’smuscles contracts and release Meibum
- Reopening phase involves activation of Levator muscle
What is a healthy blink rate?
12x/ min or every 3 - 7 secs
What are some components that can be found in the tear film?
- 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
What is the tear production rate?
1 microlitre / min
1.5mL/day
What aspects of DED do we examine clinically?
Tear drainage, tears spread and coverage, tear quality, tear production
What do we look at when examing tear production?
Blink rate
efficiency of blink
volume of tear production
What are the tests for measuring tear production?
Schirmer Test
Red phenol thread (no longer available)
tear prism height (meniscus height)
What are we looking at when we exam tear quality?
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?
What do we examine when we look at Tear and coverage?
Tear break up time (TBUT)
with slit lamp and with fluorescein
Why do we use fluroscein staining?
- it water soluble
- no sting
- will show you any TBUT and good for corneal epithelium assessment
Why do we use Lissamine Green Staining?
It has an affinity for dead or devitalised cells (doesnt stain healthy epithelial cells)
good for lid wiper epitheliopathy
good for conjunctiva assessment
Why did we use Rose Bengal Stain?
It was good for conjunctival staining.
Drawn to dead or degenerate cells.
But it stings the patient
Compare the methods for measuring Tear Volume
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?)
Describe in detail Tear Break up time.
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
What is Lip Wiper Epitheliopathy?
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.
How do you describe a lesion?
- Location (Nasal, temporal, superior, inferior) - And right eye or left eye!
- Tissue (cornea, conjunctiva, tarsus, limbus, iris etc)
- Layer (epithelium, stroma, endothelium)
- Extent (punctate, diffuse, coalescent, physical size mm x mm)
- Type (infiltrate, abrasion, nodule etc etc)
- Extra (pigment, vascularised etc)
What is to be assessed during a meiboimain gland assessement?
Assess number and quality of glands
Capping of glands
Discharge of glands
What is the purpose of conjunctival folds assessment?
Folds may represent the first stages of conjuctivochalais
associated with decreased mucin production
In what order should diagnostic tests be performed?
- 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
What is some ways to manage Aqueous DED?
Replace tears with eye drops
Preserve Tears with punctal plugs
Stimulate tears with secretagogues
What is some ways to manage Evaporative DED?
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
What are the main treatments for inflammation
Topical Steroids
Topical cyclosporine
