Lecture 10 contact lenses and dry eye Flashcards
What does a contact lens separate the tear film into?
What is each part associated with?
-pre-lens tear film: lens fit and movement
-post-lens tear film: comfort as it interacts with lids. Associated with drying/deposits.
-helps posterior lens lubrication.
What part of the tear film does the CL sit in?
aqueous tear film
Why shouldn’t tears be static in contact lens wear?
Tear exchange in important for removal of tear debris and metabolic by-products
How can a contact lens effect the tear film?
*Change in tear production (may be temporary)
*Tear film instability and evaporation
-related to lipid layer and initial tear film thickness. Layers split in 2 so is thinner.
-visual acuity may fluctuate
*Effect on tear film mucins, electrolytes and increase osmolarity
-reduced mucin so increased friction
-higher osmolarity associated with dry eye
*Blinking
What must you examine in the assessment of the tear film?
GLANDS-secretion, expression and blockages
LIDS AND LASHES- disease, position, blink rate
TEARS- volume, tear prism height, TBUT, quality, osmolarity
OCULAR SURFACE- staining, inflammation, redness
What is the purpose of the phenol red test?
How is it carried out?
-tests quantity of tears (aqueous production)
-a thread impregnated with phenol red is hooked on one side of the eyelid from lateral canthus
-important for thread not to touch the cornea as this will cause reflex tearing
-thread is yellow but becomes red when its wet with the tear film
-the test takes 15 seconds
-less than 9mm means dry eyes
What is the purpose of the Schirmer test?
How long does it take?
Why is phenol red thread test better?
-tests quality of tears
-5 minutes
-strip in schirmer test can feel uncomfortable and stimulate reflex tearing giving inaccurate tests
How does the tearscope work?
Give examples
*Produces a diffuse white reflection over the whole of the cornea using a cold cathode light source.
*Helps practitioner assess the lipid layer of the tear film.
*Flexible inserts can be placed inside the illumination tube to assess corneal distortion and damage.
oculus keratograph 5M- topographer, can examine meibomian glands, non-invasive TBUT
lipiview- can measure lipid layer thickness
inflammaDry- detects inflammatory markers of dry eye disease
tearLab-tear osmolarity- indicates osmolarity abnormalities
What can cause contact lens-related dry eye?
*If anterior surface is dry (not well lubricated cornea or not covered well), a portion of the eyelid rubs against it.
*Particularly the area near the eyelid margin
*Tear film thickness is too thin in CL wear to separate ocular surface and lid wiper.
*CL causes alteration in epithelium due to friction
What causes lid wiper epitheliopathy?
How can you assess it?
What is the treatment?
■Lid wiper is the area of epithelium in contact with the contact lens and wipes across the contact lens/eye
■Will need to evert lids to examine fully
■Stains best with lissamine green
■Treatment: lubricating eyedrops to achieve better lubrication of eye surface and reduce friction. Review to check if staining has reduced
What are lid parallel conjunctival folds (LIPCOF)?
What causes it?
What is the treatment?
How can it be graded?
*Breakdown/decrease in elastic fibres in the loose conjunctiva
*Conjunctival looseness
*Ageing or mechanical forces between conjunctiva and lower lid can cause it
*Tear deficiency and inflammation of the conjunctiva can cause it
*manage tear quality issues and rewetting drops
grade 0: no conjunctival folds
grade 1: one permanent and clear parallel fold
grade 2: two permanent and clear parallel folds (less than 0.2mm)
grade 3: more than two permanent and clear parallel folds (more than 0.2mm)
Why can Meibomian glands cause dry eye?
*Blocked glands reduce lipid quality of tears so they are more prone to evaporation
How can lifestyle cause dry eye?
*Computer vision syndrome (CVS)
*Prolonged computer, tablet, phone use
*Eye discomfort and visual problems
*Dry eyes related to blinking
What is the resting blink rate?
What can affect blinking?
why does blink rate matter in dry eye disease?
around 12x a minute
*Blink rate may change depending on activity, on cognitive or emotional function
*Increases when engaged in conversation
*When focusing on a specific visual task the blink rate may drop (CVS, 60% less blinking)
*Some diseases (e.g., Parkinson’s and schizophrenia) and medications may affect blinking
*Reduced blink rate means tear film is replenished less frequently and evaporates quicker causing ocular discomfort
What are the solutions for reduced blink rate?
*Can try blinking exercises
*20-20-20 rule
*Increase tear break up time
How can you manage dry eye in practice?
*Lens changes
*Changes to environment
*Eye drops: lubricants, lipid specific products
*Lid hygiene: lid cleansing, heat
*Diet
*MAKE SURE TO REVIEW PX
How can the environment cause dry eye?
How can you manage this?
*Contact lens discomfort increased by:
-low humidity, increased evaporation from lens
-increased airflow: change direction of blowers in the car
How can diet improve dry eye?
*Essential fatty acids are understood to enhance lipid layer of tear film-reducing evaporation
*Omega 3 – anti-inflammatory properties (avocados, walnuts, fish, plant oils)
*Omega 6 - pro-inflammatory properties
*Too much consumption of omega 6 may negate the effects of omega 3
What are the ideal properties of eye drops?
- Immediate relief
- Prolonged effect
- Non-toxic
- Doesn’t blur vision
- Inexpensive
*Higher artificial tear viscosity means tear retention time is increased and might help protect the ocular surface
*Better for overnight
-Check compatibility with contact lenses
-Recommend preservative free drops
-Ensure no other cause of symptoms like poor lens fit
What is the aim of warm compresses?
How should you do warm compresses?
*Aim of therapy is to melt the meibum to allow it to be expressed and to prevent obstruction of the terminal ducts.
-helps to alleviate evaporative dry eye?
*Temperature should be monitored, maintained for 10 minutes
*Eye bags more effective as it maintains the temperature
*Do not want to burn the eyes want to melt the meibum within the glands
How can you carry out lid hygiene?
*Lid cleaning solution with a cotton bud or cotton wool pad
*Clean lid margins (not beyond the mucocutaneous junction)
*2x daily; reduce to 1x daily as condition improves
*Use firm pressure with cotton bud to express glands
*Warm compresses to loosen collarettes and crusts. Use bephasol after this.
*Avoid use of cosmetics, especially eye liner and mascara
What is blephex?
*Physical debridement of top and bottom lids to remove the collarettes
*Useful in severe anterior blepharitis
*Requires a series of follow up treatments and use of lid hygiene to help reduce re-occurrence
