wk4: AED - Dry Eye Ax Flashcards
What are the 3 layers of the tear film and how thick are they? [important to know]
Lipid layer - 0.1um
Aqueous layer - 7um
Mucoid layer - 0.05um
Which layer of the tear film do corneal epithelial cells adhere to?
mucoid/mucin layer (adhere to membrane adherent mucins)
Explain how the lipid layer is formed as you blink (4)
Meibomian glands are found in the upper and lower eyelids
Cells on the inner wall of the meibomian gland acini produce oil
When you blink, the lids touch and pressure is applied to the meibomian glands causing them to express small amounts of this oil
The upper lid then pulls the oil upward over the eye as the eye opens
What are the roles of the 3 layers of the tear film?
Lipid layer - helps stabilise tear film and prevent evaporation of the other layers
Aqueous layer - lubricates the eye + wash away particles and prevent infection
Mucin layer - allows tear film to evenly coat cornea and interacts with aqueous layer to prevent tear film from falling off cornea (i.e. helps wettability) (via interaction and adherence to corneal epithelial cells). Also provides underlying cornea with nourishment
How many meibomian glands are present in total on the eyelids (i.e upper + lower eyelids)?
up to 100
What produces each layer of the tear film? (3)
Lipid layer - produced by meibomian glands
Aqueous layer - produced by lacrimal glands (located above the eye and towards the temples)
Mucin layer - produced by the goblet cells within the conjunctiva
Define wettability. Why is this important for our tear film?
Wetting is the ability of a liquid to maintain contact with a solid surface, resulting from intermolecular interactions when the two are brought together. The degree of wetting (wettability) is determined by a force balance between adhesive and cohesive forces.
- Important to prevent/minimise evaporation and dry eye
How can you broadly classify tear-deficient dry eye in terms of conditions? (2)
Sjogren syndrome
- (SSTD, sjogren’s syndrome tear deficiency)
- (further classifies into primary and secondary sjogren’s syndrome)
Non-sjogren sydnrome (NSTD)
How can you classify aqueous-deficient dry eye that is Not sjogren syndrome? (4)
Lacrimal deficiency
Lacrimal gland/duct obstruction
Reflex block
Systemic drugs
How can you classify evaporative dry eye? (2)
Intrinsic causes
Extrinsic causes
How can you classify evaporative dry eye caused by intrinsic causes? (4)
Meibomian oil deficiency
Disorders of lid aperture
Low blink rate
Drug action accutane
How can you classify evaporative dry eye caused by extrinsic causes? (4)
Vitamin A deficiency
Topical drugs preservatives
Contact lens wear
Systemic drugs
What is Sjogren’s syndrome?
chronic autoimmune disease characterised by degeneration of the salivary and lachrymal glands causing dry mouth/glands/eyes
What history questions might you ask if you suspect sjogren’s? (2)
Is your mouth dry?
When you go to bed at night, do you put a glass of water on the bedstand?
What is the Schirmer test?
Is where a paper strip is inserted into the eye (lower eyelid pouch) for several minutes to measure the production of tears. (eyes are closed for 5 minutes during this specifically). The paper is then removed and amount of moisture is measured
What will a schirmer test result look like in patients with sjogren’s
“the paper strip will come out bone dry” - Darryl Guest (because these patients don’t produce tears)
guidelines say anything less than 5ml can be marked as sjogren’s syndrome (if they get more than 5ml then they pass and don’t have sjogren’s syndrome, but that doesn’t mean they don’t still have dry eye)
How do you interpret the results of the Schirmer Test? (from wiki) (4)
Normal: >/= 15ml
Mild: 14-9ml
Moderate: 8-4ml
Severe dry eye: <4ml
*after 5 minutes
And, sjogren’s: expect <5ml (but that doesn’t necessarily mean sjogren’s if they get like 3ml or something, if they get 0ml however it’s quite more likely)
What 2 clinical actions should you do when assessing if something is an autoimmune disease?
History taking (incl family hx)
Blood test
How does corneal sensitivity relate to the tear film?
anything that effects corneal sensitivity will affect the tear film. You need some kind of corneal sensitivity to produce a tear film
Is there an inflammatory component to dry eye?
yes
At what percentage of humidity to humans start getting dry eye symptoms? What is the percentage of humidity in a plane?
Below 40%. Humidity in a plane is 28% so yeah everyone on the plane be getting dry eye
What percentage of the population is estimated to have dry eye? How can you explain this percentage?
About 30%. The reason this is so high might be due to over-diagnosis of dry eye by doctors following trends and fads. There’s probably only about 15-20% that actually have significant dry eye
In the DEWS-II dry eye work up flowchart, list the steps leading to the diagnosis of a normal patient (4)
Presenting patient
Asymptomatic
No signs of ocular surface disease
Normal Patient (no tx required)
In the DEWS-II dry eye work up flowchart: how do you classify a patient with signs of ocular surface disease? (2)
signs without symptoms: predisposition to dry eye
neurotrophic conditions (dysfunctional sensation)
In DEWS-II: how do you manage a patient with signs of ocular surface disease but without symptoms? (1)
Preventative management as appropriate (e.g. post-surgery)
In DEWS-II: how do you manage a patient with signs of ocular surface disease and subsequent neurotrophic condition? (1)
signs indicated management of DED required
In the DEWS-II dry eye work up flowchart: How can we classify a symptomatic patient? (2)
signs of ocular surface disease
no signs of ocular surface disease
In the DEWS-II dry eye work up flowchart: how can you classify a symptomatic patient with no signs of ocular surface disease? (2)
symptoms without signs: pre-clinical state
neuropathic pain (non-OSD)
In DEWS-II: if you have a symptomatic patient with signs of ocular surface disease - what should you do? (1) What does this accomplish? (1)
Ask Triaging questions to differentially diagnose other ocular surface diseases
In DEWS-II: How should you manage a symptomatic patient with no signs in the pre-clinical state? (3)
Observe/offer education/preventative therapy
In DEWS-II: How should you manage a symptomatic patient with neuropathic pain? (1)
Refer for pain management
List 4 general causes of dry eye
reduced aqueous production
mucin deficiency
lipid deficiency
lid/ocular surface abnormality
List 2 general examples of a primary cause of reduced aqueous production
gland dysfunction
gland blockage
List a general example of a secondary cause of reduced aqueous production
abnormal neural reflex/control
What can cause a mucin deficiency? (1)
goblet cell dysfunction
What can cause a lipid deficiency? (1)
MGD (meibomian gland dysfunction)
How can you classify lid/ocular surface abnormalities? (2)
neural abnormality
structural abnormality
What systemic condition is sjogren’s syndrome most commonly associated with? Provide the percentage
70% of sjogren’s is associated with rheumatoid arthritis
List 7 examples of reduced aqueous production
primary sjogren’s syndrome
secondary sjogren’s syndrome (e.g. rheumatoid arthritis)
systemic or topical drugs
lacrimal gland tumours
lacrimal gland inflammation/trauma
neural dysfunction/tumour
desensitised cornea
Why might someone have a desensitised cornea? (2)
e.g. due to:
contact lens wear
surgery (such as laser surgery)
What type of stain does Tim the lecturer not like?
Lissamine Green. “I’m not a fan of that” - Tim. “But UMEyecare have the good lissamine, so use theirs”
Name 2 lifestyle causes of vitamin A deficiency
Alcohol drinking - alcohol strips vitamin A out of the system
Liver cleansing diet - px doesn’t get all the vitamins they need
How can long term vitamin A deficiency present physically as a telltale sign? (1)
pigmentation on the cheeks
List 3 causes of a mucin deficiency
vitamin a deficiency
systemic or topical drugs
severe ocular surface inflammation/trauma
What type of dry eye would someone with a mucin deficiency get?
aqueous dry eye (b/c remember mucin layer helps with wettability)
List 3 causes of lipid deficiency
lid disease/meibomian gland dysfunction
systemic or topical drugs
lid inflammation/trauma
Name a type of drug that is a common cause of lipid deficiency
Acne medication. So if patient is taking acne medication it might be a good idea to check for dry eye!
How does your rate of blinking change when staring at something?
drops to about 40% of normal blink rate
Name 6 causes of blink abnormalities
desensitised cornea
bell’s palsy
concentrated use of eyes/staring (e.g. TV)
coma
parkinson’s disease
systemic drugs
Name 5 causes of eyelid malposition
exophthalmos
ectropion
entropion
lagophthalmos
bell’s palsy
What is the most common cause of bell’s palsy development in young people? in old people?
Young people: pregnancy
Old people: HSV
Name 6 causes of ocular surface disruption
contact lenses
filtering bleb (i.e. in glaucoma)
pterygia/pingueculae
tumours
trachoma + other scarring
inflammation (e.g. S-JS)
How useful is fluoroscein in dry eye diagnosis?
Not that useful. Fluoroscein is only useful to look at problems you already saw/know about. In fact, the process of putting in fluorescine will actively disrutp the tear film.
Can illness effect dry eye and tear film?
yep. Absolutely. Can use temporary drops to manage
What triaging questions do you ask in diagnosis of dry eye? (8)
How severe is eye discomfort?
Any mouth dryness or swollen glands?
How long have symptoms lasted + any triggering event?
Is vision affected + does it clear on blinking?
Are symptoms or redness worse in one eye than other?
Do eyes itch, appear swollen or crusty, or discharge?
Do you wear contact lenses?
Any general health conditions (incl respiratory) or taking medications?
When should you use fluoroscein?
Only when non invasive tear breakup time is not available
Name the homeostasis marker tests for dry eye (3)
NITBUT - non invasive tear breakup time (alternatively fluoroscein TBUT)
Osmolarity
Ocular surface staining
If you use multiple homeostasis marker tests for dry eye, what order should they be performed in? (3)
- NITBUT
- Osmolarity
- Fluorescein TBUT
- Ocular surface staining
Provide 3 example risk factors for dry eye
smoking
certain medications
contact lens wear
What tear meniscus heights (TMH) represent mild, moderate, and severe aqueous deficient dry eye? (3)
Mild - 0.2mm
Moderate - 0.1mm
Severe - 0.0mm
What does Darryl Guest think about fluorescein breakup time?
He HATES it. However he says that students have gotten red flagged in the past for not suggesting fluoroscein tear breakup time
What is the cut-off finding values for the following tests for dry eye?:
fluourecein TBUT
NITBUT
Osmolarity
LWE (lid wiper epitheliopathy)
Schirmer
LIPCOF
Fluoroscein TBUT: — nothing written here
NITBUT – 2.7s to 10s
Osmolarity – >308mOsm/L
LWE – .2mm
Schirmer – severe <5mm
LIPCOF – level 2
What dry eye measurements are rated the highest on Darryl Guest’s usefulness scale? (2)
NITBUT and Osmoolarity
List 7 symptoms of dry eye?
Usually bilateral if asymmetric
Scratchy, burning, gritty, FB sensation
Worse on waking, in hot dry locations, in air-conditioned rooms, in smoky areas, windy env., low humidity, and when working on computer
Excessive tearing
Mucous discharge
Mild to moderate loss of vision with variability
CL intolerance
What is a positive result for dry eye on the DEQ-5 Questionnaire?
a score of 6
List 8 signs of dry eye?
excess mucous, debris, foam or oil in tear film
reduced/absent tear prism/meniscus (<1mm)
reduced response to phenol red thread or schirmer test, reduced TBUT (<10 seconds)
characteristic conjunctival staining
conjunctival hyperaemia, wrinkles, scarring or attachments
corneal erosion/ulceration/infiltration, filaments, vascularisation, scarring, keratinisation
blurred or fluctuating vision
lid disease
