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OD2 (S1&2) > CLM - Soft Contact Lens Maintenance - Week 8 > Flashcards

CLM - Soft Contact Lens Maintenance - Week 8 Flashcards

1
Q

List 6 key requirements for contact lens solutions.

A

Antimicrobial efficacy
Non-toic to ocular tissue
Minimum effect on lens parameters
Simple to use
Convenient
Inexpensive

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2
Q

List 7 possible components of a contact lens solution.

A

Water
Osmolarity adjusting agents
Buffering agents
Surfactants
Preservatives/disinfectants
Chelating agents
Viscosity enhancing agents

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3
Q

Give an example of an osmolarity adjusting agent and an ideal percentage. What else can it be used for?

A

Sodium chloride, adjusts tonicty to the same level as tears, ideally 0.9-1.1%
Can be used in much larger amounts to enhance cleaning/antimicrobial action (hypertonic)

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4
Q

What is a buffer solution and what doth it do?

A

A combination of weak acids or bases and their salts
This stabilises and maintains preferred solution pH under varying conditions

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5
Q

What determines the buffer and final pH to be used in a contact lens solution?

A

The preservative type

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6
Q

List the 5 components of lens care routine.

A

Handwashing
Surface cleaning
Rinsing
Disinfection
Enzymatic cleaning
Case care

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7
Q

When handwashing, what should be avoided?

A

Soaps with added moisturisers/perfumes/scents etc

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8
Q

What is the most important step in lens care routine?

A

Surface cleaning

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9
Q

What log unit reduction in microorganisms occurs with surface cleaning?

A

2-4 log unit reduction, up to 99.9% removal

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10
Q

Whats more important, the cleaning process of a lens or the brand of cleaner used?

A

Cleaning process

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11
Q

When must surface cleaning be done?

A

Every time the lenses are taken off.

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12
Q

What is surface cleaning typically conducted with?

A

Multipurpose solutions, but daily cleaners are available

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13
Q

What is the purpose of rinsing after surface cleaning?

A

Flush loosened debris and remove cleaner

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14
Q

What occurs with disinfection? Is sterilisation achieved?

A

Reduction of microbial contamination to safe levels, inactivating all pathogenic microorganisms, but not all microbial forms
Sterilisation is not the aim, and is not achieved

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15
Q

What is the mosr common form of contact lens disinfection? How is microbial death achieved (2)?

A

Chemical disinfection
Dissolves cell membrane lipids
Denatures proteins essential for function

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16
Q

List 4 physical methods for soft contact lens disinfection. Is this common?

A

Thermal
Microwave
Ultraviolet
Ultrasound
Rare now

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17
Q

List 5 types of chemical methods for soft contact lens disinfection.

A

Biguanides
Quaternary ammonium compounds
Hydrogen peroxide
Sorbic acid
Thimerosal (autistic screeching)

18
Q

What is an advantage of disinfection using microwaves?

A

Effective and rapid elimination of bacteria via inhibition of metabolism

19
Q

What are 4 disadvantages of disinfection using microwaves?

A

Long term effect on lens polymers could be damaging
Difference in microwave brands/outputs etc
Initial cost of the microwave
Lack of portability

20
Q

Describe hydrogen peroxide as a disinfectant.

A

Strong oxidising agent at 3%
Toxic to the eye and requires inactivation using a tablet or liquid or platinum

21
Q

What is the minimum soaking time in hydrogen peroxide before neutralising? What is recommended?

A

Minimum 3 hours
6 hours recommended (overnight)

22
Q

List 4 advantages of hydrogen peroxide for contact lens disinfection.

A

Preservative free
Broad antimicrobial efficacy
Creat for conventional soft lenses
Less staining than chemical solutions for SiH lenses

23
Q

List 4 disadvantages of hydrogen peroxide for contact lens disinfection.

A

Residual peroxide may cause discomfort and hyperaemia
Little to no ongoing disinfection capability
Expensive
More difficult/lower compliance (not with the one step system)

24
Q

List two old generation disinfectants and why they are classed so. What to new generation disinfectants have that prevents this?

A

Chlorhexidine and thimerosal
Due to uptake into the lens matrix
Newer generation disinfectants have larger molecules, minimising absorption

25
Q

Are bacteria and/or viruses superficial on the lens? Can they fit into the pores of the lens and infiltrate the matrix?

A

No, they are superficial on the lens and cant fit into the pores

26
Q

What are biguanides?

A

Cationic antiseptics

27
Q

Do biguanides have a large or small molecular size? How long does it take to achieve disinfection?

A

Large, disinfection takes 4-6 hours

28
Q

What is a disadvantage of biguanides?

A

Small percentage of patients show sensitivity, some issues with SiH lenses

29
Q

What are quaternary ammonium compounds and what are they effective against? How long do they take to disinfect?

A

Cationic detergents, effective against bacteria and fungi
Takes 6 hours to disinfect

30
Q

List 4 advantages of multipurpose solutions.

A

Convenience
Reduced cost
Eliminate saline
Enhance compliance

31
Q

List two disadvantages of multipurpose solutions.

A

Possible compromised efficacy
Solution toxicity/sensitivity

32
Q

Compare multipurpose solutions to hydrogen peroxide in terms of corneal staining caused.

A

Multipurpose solutions cause significantly more asymptomatic corneal staining than hydrogen peroxide for SiH lenses

33
Q

What is still required with no rub solutions? Is it better than rubbing?

A

Still requires significant rinsing procedure, as long as 20 seconds
Rubbing is always better

34
Q

What is better for SiH, multipurose solutions or hydrogen peroxide?

A

Hydrogen peroxide

35
Q

What is recommended for lenses not replaced daily in terms of cleaning (2)?

A

Separate daily cleaner and enzyme cleaning

36
Q

What do enzymatic cleaners do?

A

Removes bound insoluble protein

37
Q

What increases with the age of a contact lens?

A

Immunogenic potential of bound proteins

38
Q

What should always be done before and after enzymatic cleaning?

A

Surface clean and rinse

39
Q

How are cases cleaned (3)?

A

Hot tap water
Disinfecting solution/saline and toothbrush/cotton-bud
Air drying

40
Q

How often should lens cases be replaced?

A

Every 3 months

41
Q

How do antibacterial lens cases work? What is needed for it to maintain activity?

A

Contains silver which is broad spectrum
Requires moisture to maintain activity

42
Q

List 7 uses for rewetting drops.

A

Alleviating dryness/discomfort
Flushing irritating particles from the eye/lens
Rehydrating lenses
Marginal dry eye patients
Dry/windy conditions
Tired eyes
Mild allergy symptoms

OD2 (S1&2) (174 decks)

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