3.1.7 Assesses Tear film Flashcards
When assessing the tear film, what facts need to be known
- Debris in tear film may be from bleph
- General Anatomy & Physiology of the Tear Film:
- Lipid 0.1 (micrometres), Aqueous (7.0) & Mucin Layers (0.02-0.05?)
- Contact lens wear significantly disrupts the TBUT. Pre & post tear film not the same. Lipid layer becomes thinner, increasing evaporation
- Tear scope
- Must assess tear quality & quantity
- Learn difference between Quantitative & Qualitative e.g. Tear quality is Qualitative (Aqueous deficient or Evaporative) & TBUT is Quantitative (quantifying the stability of the tears)
What are the 3 layers of the tear film and their: Origin, components and functions
Lipid Layer:
Origin: Meibomian glands
Major components: Cholesterol esters, ester waxes
Functions: Avoids evaporation, provides optically smooth surface
Aqueous Layer:
Origin: Lacrimal glands
Major components: Water, Protein, Salts
Functions: Bacteriostasis, Debris flushing, Maintenance of epithelial hydration
Mucus Layer:
Origin: Conjunctival goblet cells, Glads of Moll and Krasse
Major components: Glycoprotein
Functions: Renders epithelial surface hydrophilic for aqueous to be wet
More Complete Dry eye assessment
- Non-invasive to Invasive:
- H&S!!!
- White light slit lamp exam - Tear quality with optic section/specular reflection at 16X, Tear meniscus height (<0.18mm is dry), Looking out for signs of blepharitis on eyelashes, eyelid margins. Looking at any redness of conjunctiva, limbus & lids. Looking out for any signs of keratitis on cornea. Can also look at LIPCOF
- Blue light slit lamp exam - Instill NaFl. Preferably using wratten filter. Looking for signs of staining suggests dryness present/more longstanding e.g. smile stain. TBUT - watching for when the tear film breaks up, may use 10X mag to observe this more easily.
- Lid eversion - Looking for signs of papillae, follicles etc. Especially if patient presents with itchiness &/or mucous discharge. Grading roughness, redness & noting any papillae etc.
Consistent non-modifiable causes of dry eye
- Aging
- Female
- Asian
- Meibomian gland dysfunction
- Connective tissue diseases
- Sjogren syndrome
consistent modifiable causes of dry eye
- Computer use
- Contact lens wear
- Hormone replacement therapy
- Hematopoietic stem cell transplantation
- Environmental: Pollution, low humidity, sick buildingg sundrome
- Medications: Antihistamines, antidepressants, anxiolytics, isoretinoin
Probable causes of dry eye disease
Modifiable
Low fatty acid intake
Refractive surgery
Allergic conjunctivitus
Medications: anticholinergic, diuretics, beta blockers
Non-modifiable
Diabetes
Roscacea
Viral infection
Thyroid eye dsease
Psciatric conditions
Pterygium
What can affect the upper & lower lid?
- Papillae - Papillary, Allergic, Atopic, Bacterial, Gonoccocal conjunctivitis, Blepharitis
- Follicles - Viral conjunctivitis, Molluscum, Chlamydia
Tear Volume
0.2-0.3mm normal, <0.18mm dry eye - aqueous deficient
Tear Quality
- Tearscope - attached to slit lamp to evaluate lipid layer & NITBUT
- Optic section/specular reflection - slow debris movement, marble like appearance
- More debris than there should be may be debris from blepharitis
Tear Osmolarity
- Tear lab used
- 308 mOsm/l is the most sensitive threshold todistinguish normal from mild/moderate DED, while 315 mOsm/l is the most specific cut-off
Non invasive TBUT
- Using a keratometer or grid from topographer or tearscope
- 20-40 seconds normal, 10-15 borderline? <10 dry eye
Schirmer test
- For severe dry eye (aqueous) - Sjogrens
- Strip put into inferior fornix for 5 mins! No anaesthetic
- > 10mm normal, 5-9 borderline, <5 dry eye
- Low sensitivity test so doesn’t pick up many dry eye cases. High specificity so few false positives
Phenol red
- Alkaline yellow strip into inferior fornix turns red
- Put for 15 seconds
- 11-18mm normal but <10mm is dry
NaFl TBUT
- Destabilises tear film so non invasive best to start with otherwise inaccurate
- 10 or higher is good
- 5-9 secs is borderline, <5 is dry
