Week 8 - Dry eye in CL wear Flashcards
What is the tear film essential for?
• Antibacterial properties
• Transporting nutrients to the cornea
• Optical performance of the eye
• Successful contact lens wear
Dry eye is due to disorder or disturbance of tear film
What is dry eye disease (DED)
• Characterised by a dysfunction of one or more of the components of the tear film
• Multifactorial
What is the purpose of the outer oily layer, watery middle layer and inner mucous layer in the tear film?
An outer oily layer
• Produced by meibomian glands
• Smoothes the tear surface and | evaporation
A watery middle layer
• Produced by lacrimal gland
• Carries nutrients and oxygen to the cornea
• Washes away particles and irritants
An inner mucous layer
• Produced by conjunctiva
• Provides protection and ensures eye remains moist
• Vital for stability
what are the symptoms of dry eye?
• Grittiness
• Foreign body sensation
• Lacrimation
• Itching
• Blurred vision
• Redness
• Photophobia (usually not severe)
What are the signs of dry eye?
• Conjunctival hyperaemia
• Reduced tear film break-up time (TBUT)
• Corneal and conjunctival staining
• Reduced tear volume
• Signs of anterior bleph/MGD
What is tear film break up?
• Initially tear film thin by evaporation
• Some lipid molecules are then attracted to the mucin layer and begin to migrate to this layer
• When mucin layer is fully contaminated by lipid, mucin becomes hydrophobic and tear film ruptures
what % or CL wearers are affected by DED?
• 20-75% of CL wearers
• 11-35% of non-CL wearers
What are the causes of DED in CL wear?
• blink efficiency
- Frequency
- Completeness
• Material dehydration
- fitting changes
- epithelial staining
• Increase in deposits
• Decrease wettability
What things need to be ruled out in CL wear + dryness?
Need to rule out:
• Poor fitting
• Manufacturing problems
What effect does CL have on tear film?
• Destabilisation
• Decreased TBUT
• Decreased tear volume (may be insufficient to cover CLs adequately)
• Decreased lipid layer
• Stagnation of the post-lens tear film
• Increased tear evaporation rate (esp. SCLs)
What effect does CL have on Lids?
• Altered tear menisci
• Increased blinking (to resurface the eye)
• Incomplete blink amplitude
• Lid conformance to the eye may be impossible -> 3 & 9 stainin‹
(RGPs)
What effects do SCL have on tear film?
• Increased evaporation
• Decreased tear film stability(<6sec not uncommon)
After 6 months of SCL wear:
- Decreased BUT by 3 sec, and..
- Increased DED incidence from 28% (before SCLs) - 68% (after SCLs)
Effect of RGP’s on the Tear Film?
Lids unable to conform to shape of lens-anterior eye:
-> 3 & 9 staining
-> lens adherence
Post-lens tear film stagnation by restricting tear exchange
Tear film continuity more difficult to maintain
- Increased edge clearance
- thicker edges
- Increased lens mobility
Increased foreign bodies & contaminants move and destabilise tear film
Which wearers should be eliminated in wearer selection?
• those with marked tear instability
• the deposit prone
• NIBUT < 10 seconds
• Be wary of NIBUT 10 - 20 seconds
• Happy with those with NIBUT > 20 seconds
• Significant blepharitis
What things can be changed when managing SCLs?
Aim to reduce tear film evaporation
• Material : Less charged ion materials attract less deposits
• Lens thickness (thickest)
• Water content (lowest water content)
• Wearing schedule (minimal)
• Lubrication (non-preservative)
• Preservative free lens care products
• Refit with RGP lenses if unsuccessful
• Frequent replacement to decrease deposits, increase TBUT
How are RGP’s managed?
Need to minimise 389 staining
- centration (higher riding)
- total diameter (larger)
- edge thickness (minimal)
N.B. rigid lenses are better for DED because:
• Increase tear exchange
• no evaporation staining
What points need to be considered when choice of CL care products?
• Avoid using products containing older-generation preservatives/disinfectants:
- Thimerosal
- Chlorhexidine
- Benzalkonium chloride
• Choose those with lubricating/re-wetting function incorporated
What is important about Re-wetting drops?
• Benefits last only up to 5 minutes
- Tear film stabilized for 5 min
- No effect on lens hydration
• Use unpreserved products where possible
- Usually preferred by users
- BAK, etc. injurious to the cornea
- Long-term effects of preservatives on the cornea?
How is DED managed in CL wearers?
• Comfort drops?
• Cease wear?
- If ocular surface is compramised
• Different lens/modality/schedule?
How are problems prevented?
• Identifying borderline CL candidates
- predictive testing
- history
• Treating conditions in advance
- Meibomian gland dysfunction
- Blepharitis
• Tear supplements
• Punctal plugs (??)
• Adapting to circumstances
- patient expectations
- environmental changes
• Lens replacement
- optimal schedule
what are existing dry eye and CL wear prognosis?
• DE may increase the risks
- Risk of infection
- Due to change in tear proteins (decreased antibacterial)
• Risk of lens fitting problems
- Decentration
- Excessive movement
- Adherence
