Week 8 - Dry eye in CL wear

Question 1

What is the tear film essential for?

Answer 1

• 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

Question 2

What is dry eye disease (DED)

Answer 2

• Characterised by a dysfunction of one or more of the components of the tear film
• Multifactorial

Question 3

What is the purpose of the outer oily layer, watery middle layer and inner mucous layer in the tear film?

Answer 3

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

Question 4

what are the symptoms of dry eye?

Answer 4

• Grittiness
• Foreign body sensation
• Lacrimation
• Itching
• Blurred vision
• Redness
• Photophobia (usually not severe)

Question 5

What are the signs of dry eye?

Answer 5

• Conjunctival hyperaemia
• Reduced tear film break-up time (TBUT)
• Corneal and conjunctival staining
• Reduced tear volume

• Signs of anterior bleph/MGD

Question 6

What is tear film break up?

Answer 6

• 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

Question 7

what % or CL wearers are affected by DED?

Answer 7

• 20-75% of CL wearers
• 11-35% of non-CL wearers

Question 8

What are the causes of DED in CL wear?

Answer 8

• blink efficiency
- Frequency
- Completeness

• Material dehydration
- fitting changes
- epithelial staining

• Increase in deposits
• Decrease wettability

Question 9

What things need to be ruled out in CL wear + dryness?

Answer 9

Need to rule out:
• Poor fitting
• Manufacturing problems

Question 10

What effect does CL have on tear film?

Answer 10

• 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)

Question 11

What effect does CL have on Lids?

Answer 11

• Altered tear menisci
• Increased blinking (to resurface the eye)
• Incomplete blink amplitude
• Lid conformance to the eye may be impossible -> 3 & 9 stainin‹
(RGPs)

Question 12

What effects do SCL have on tear film?

Answer 12

• 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)

Question 13

Effect of RGP’s on the Tear Film?

Answer 13

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

Question 14

Which wearers should be eliminated in wearer selection?

Answer 14

• 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

Question 15

What things can be changed when managing SCLs?

Answer 15

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

Question 16

How are RGP’s managed?

Answer 16

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

Question 17

What points need to be considered when choice of CL care products?

Answer 17

• Avoid using products containing older-generation preservatives/disinfectants:
- Thimerosal
- Chlorhexidine
- Benzalkonium chloride

• Choose those with lubricating/re-wetting function incorporated

Question 18

What is important about Re-wetting drops?

Answer 18

• 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?

Question 19

How is DED managed in CL wearers?

Answer 19

• Comfort drops?
• Cease wear?
- If ocular surface is compramised
• Different lens/modality/schedule?

Question 20

How are problems prevented?

Answer 20

• 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

Question 21

what are existing dry eye and CL wear prognosis?

Answer 21

• 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