13. CL IX - Soft CL Maintenance

Question 1

Why do we need to know about contact lens solutions?

Answer 1

Emphasis on prescribing a contact lens regime to know how to mitigate complications, infections, and hypersensitivity whilst increasing compatibility.

Question 2

Sterilisation vs Disinfection

Sterilisation is ... or ... all forms of life; can be done via ..., ..., or ....

Disinfection ... microorganisms and ... all/most ... microorganisms. There is this idea of ... vs ... disinfectants.

Answer 2

Sterilisation vs Disinfection

Sterilisation is killing or deactivating all forms of life; can be done via extreme heat, high pressure, or irradiation.

Disinfection reduces microorganisms and eliminates all/most pathogenic microorganisms. There is this idea of bactericidal vs bacteriostatic disinfectants.

Question 3

Disinfection vs Preservation

Disinfection ... harmful microorganisms via ... or ... methods whereas preservatives ... of microorganisms.

Often the ... in ... and manufacturers have to balance ... vs .../....

Answer 3

Disinfection vs Preservation

Disinfection eliminates harmful microorganisms via physical or chemical methods whereas preservatives control the growth of microorganisms.

Often the same chemical in higher doses and manufacturers have to balance effectivity vs safety/toxicity.

Question 4

What are the key solution requirements:

For the solution: ..., ... to ocular tissues, minimum effect on ..., ..., ..., ..., ....

To the patient: ..., ..., ..., ....

To the practitioner: ..., ..., ....

Answer 4

What are the key solution requirements:

For the solution: antimicrobial efficacy, non-toxic to ocular tissues, minimum effect on lens parameters, simple to use, convenient, inexpensive, comfortable.

To the patient: cost, speed, comfort, simplicity.

To the practitioner: efficacy, compatibility, compliance.

Question 5

What are the possible ingredients in contact lens solutions?

..., ..., ..., ..., ..., ..., .../....

Components are regulated by ... and ....

Answer 5

What are the possible ingredients in contact lens solutions?

Water, osmolarity adjusting agents, buffering agents, surfactants, chelating agent, viscosity enhancing agents, preservatives/disinfectants.

Components are regulated by FDA and ISO.

Question 6

Osmolality adjusting agents

Used in ... amounts in solutions that come in ... with the eye. They adjust ... to match the tears and ... ocular comfort. They assist in ... of the lens on the eye.

The ideal level is ...-...% and can be used in higher concentrations to ... and/or ....

Answer 6

Osmolality adjusting agents

Used in small amounts in solutions that come in direct contact with the eye. They adjust tonicity to match the tears and increase ocular comfort. They assist in rapid settling of the lens on the eye.

The ideal level is 0.9-1.1% and can be used in higher concentrations to enhance cleaning and/or antimicrobial action.

Question 7

Buffering agents control the ... of solutions; an incorrect ... can result in ... on the eye. Consist of a combination of weak ... or ... (and their ...) to ... and ... the ... under varying conditions.

Ideal range is ...-... if used in direct contact with the eye; increases ... and assists in ... on the eye.

Preservative type will determine the buffer/s used:
* ... are incompatible with ...
* ... and ... are stable at neutral pH
* ... is more effective at low pH level

Answer 7

Buffering agents control the pH of solutions; an incorrect pH can result in tightening of the lens on the eye. Consist of a combination of weak acids or bases (and their salts) to stabilise and maintain the preferred pH under varying conditions.

Ideal range is 6.6-7.8 if used in direct contact with the eye; increases ocular comfort and assists in rapid settling of lens on the eye.

Preservative type will determine the buffer/s used:
* Borates are incompatible with benzalkonium chloride (BAK)
* Chlorhexidine and thimerosal are stable at neutral pH
* Chlorbutanol is more effective at low pH level

Question 8

Other agents in contact lens solutions - further detail

Surfactants: detergent ... and ... surface ... and aids with ...

Viscosity-enhancing/wetting agents: enhances ... and ... of contacts

Chelating agents: link together ... and removes ...; key one to remember is ...

Preservatives/disinfectants: ...

Answer 8

Other agents in contact lens solutions - further detail

Surfactants: detergent loosens and removes surface deposits and aids with wetting of surfaces

Viscosity-enhancing/wetting agents: enhances biocompatibility and wettability of contacts

Chelating agents: link together metal ions and removes proteins; key one to remember is EDTA

Preservatives/disinfectants: antimicrobial activity

Question 9

Hand washing

Must be performed before ... or ... of the lens. Removes ... and decreases ... on the hands but have to avoid soaps with added ... and ... as they give an ... that can cause a .... Don’t use ... or ... and dry them with a ... or ....

Answer 9

Hand washing

Must be performed before any handling or manipulation of the lens. Removes dirt and decreases bacterial levels on the hands but have to avoid soaps with added moisturisers and perfumes as they give an oil feeling that can cause a burning sensation. Don’t use handsanitisers or wipes and dry them with a paper towel or dry towel.

Question 10

What are the 6 steps of lens care routine?

Answer 10

• Hand washing
• Surface cleaning
• Rinsing
• Disinfection
• Enzymatic cleaning
• Case care
• Proper storage.

Question 11

Surface cleaning

This is the ... step; removal of .... Effect of rubbing lens increases from ...% to ...% compared to rinsing alone. Proper sequence is essential as it prepares the lens for ... (... -> ... -> ...). Done in the ... and must be done .... Typically conducted with a .... ... is desirable to remove ..., ..., and .... Surfactants and detergents break up ... via ....
Daily cleaners are used ... because some people have ... or general ... in their tears.

Process: 1. ..., 2. ..., 3. ..., 4. ..., 5. ...

Answer 11

Surface cleaning

This is the most important step; removal of loosely adherent deposits, debris, and contaminants. Effect of rubbing lens increases from 99% to 99.9% compared to rinsing alone. Proper sequence is essential as it prepares the lens for disinfection (rub -> rinse -> disinfect). Done in the palm of the hand and must be done every time the lenses are removed and are to be used again. Typically conducted with a MPS. Broad efficacy is desirable to remove mucus, lipids, and proteins. Surfactants and detergents break up deposits via micelle formation.
Daily cleaners are used in conjunction with MPS because some people have more protein or general debris in their tears.

Process: 1. wash hands, 2. place lens in palm, 3. place 2-3 drops of solution on both lens surfaces, 4. rub each side for ~15secs, 5. rinse well

Question 12

Rinsing

... loosened debris and removes .... Comes as .../... saline and ... saline. It has no ....

Answer 12

Rinsing

Flushes loosened debris and removes cleaner. Comes as preserved/aerosol saline and unpreserved saline. It has no disinfecting properties.

Question 13

Disinfection and storage

Disinfection: reduction of ... to a safe level

Storage: maintain ... until next application; storage of contacts in ... or ... does not provide required ... or ...

Answer 13

Disinfection and storage

Disinfection: reduction of microbial contamination to a safe level

Storage: maintain lens hydration until next application; storage of contacts in water or saline does not provide required disinfection or preservation

Question 14

... disinfection is more common than .... Chemical disinfection kills microbes by ... and ... essential for function.

Methods of SCL disinfection:
Physical: ..., ..., ..., ...
Chemical: ..., ..., ..., ..., and ...

Answer 14

Chemical disinfection is more common than physical disinfection. Chemical disinfection kills microbes by dissolving cell membrane lipids and denaturing proteins essential for function.

Methods of SCL disinfection:
Physical: thermal, microwave, ultraviolet, ultrasound
Chemical: biguanides, quaternary ammonium, hydrogen peroxides, sorbic acid, and thimerosal

Question 15

Thermal disinfection - ... disinfection

Advantages: ... and ... elimination of bacteria via ...

Disadvantages: ..., ... between brands, ... of the microwave, lack of ...

Answer 15

Thermal disinfection - physical disinfection

Advantages: effective and rapid elimination of bacteria via inhibition of metabolism

Disadvantages: long term effect on lens, differences between brands, initial cost of the microwave, lack of portability

Question 16

Ultraviolet disinfection - ... disinfection

UV-C PuriLens - lens hold prevents ... and uses a ... for disinfection. Disinfection via ... but ... is required.

Answer 16

Ultraviolet disinfection - physical disinfection

UV-C PuriLens - lens hold prevents direct lens exposure and uses a subsonic agitation cleaning mechanism for disinfection. Disinfection via continuous sterilisation of the soaking solution but power is required.

Question 17

1step vs 2step hydrogen peroxide systems, what needs to happen in either case?

Answer 17

1step is neutralisation of H2O2 after coming into contact with a platinum disc whereas 2 step is soaking the contact in a H2O2 solution for 3-5 hours (minimum 3hours) and then adding a tablet to neutralise the H2O2. 1step system is neutralised slower.

Either way, need to use them immediately or store them in disinfecting/preservative solution until ready to wear again.

Question 18

What are the kill times in H2O2 for the following microorganisms?

Bacteria: ... min
Viruses: ... min
Fungi: ... min
Acanthamoeba: ... hours
Spores: ... hours

Answer 18

What are the kill times in H2O2 for the following microorganisms?

Bacteria: 10-15 min
Viruses: 10-15 min
Fungi: 60 min
Acanthamoeba: 1-2 hours
Spores: 5 hours

Question 19

Hydrogen Peroxide - ... disinfection

H2O2 is ... to the eye and requires ... after disinfection. Used in a ...% solution and is neutralised into ... and ... via a ... or ....

Advantages: ..., ..., great for ..., and ... than chemical solutions

Disadvantages: residual peroxide may cause ... and ..., minimal exposure to peroxide with ..., ..., and ....

Answer 19

Hydrogen Peroxide - chemical disinfection

H2O2 is toxic to the eye and requires inactivation after disinfection. Used in a 3% solution and is neutralised into water and oxygen via a catalase tablet or platinum disc.

Advantages: preservative free, broad antimicrobial efficacy, great for conventional soft lenses, and less staining than chemical solutions

Disadvantages: residual peroxide may cause discomfort and hyperaemia, minimal exposure to peroxide with 1step system, little to no ongoing disinfection capability, and more difficult and complicated.

Question 20

Do you need to change the H2O2 1system case?

Answer 20

Shouldn’t need to replace case given platinum won’t be used up in reaction and H2O2 can kill everything, but change just to be safe (just in case of plastic degradation?)

Question 21

Multipurpose solutions - ... disinfection

Older generation disinfectants: .../... reactions due to ... in the ... as they are ... with .... E.g. ... and ...

Newer generation disinfectants have ... with ... which minimises ....

Answer 21

Multipurpose solutions - chemical disinfection

Older generation disinfectants: toxicity/hypersensitivity reactions due to uptake in the lens matrix as they are smaller molecules with low molecular weight. E.g. chlorhexidine and thimerosal

Newer generation disinfectants have larger molecules with high molecular weight which minimises absorption.

Question 22

How does toxicity from disinfectants occur to the eye ball and do we need disinfectants to penetrate the lens matrix?

Answer 22

Toxicity occurs from prolonged contact due to accumulation in the contact; H2O2, chlorhexidine, and thimerosal build up in the contact because their molecule size is smaller than the CL pore size.

Systems don’t need to penetrate the lens matrix as most bacteria/viruses can’t penetrate the contact.

Question 23

Biguanides - ... disinfection

They are ... antiseptics (... biguanide, ... biguanide, ..., and ...). These polymers are incorporated into the ... which results in .... They also bind to ... to ... and they also .... They have ... molecules and a small percentage of patients show ....

Can be found by itself or in a dual status with ... compounds.

Answer 23

Biguanides - chemical disinfection

They are cationic antiseptics (polyaminopropyl biguanide, polyhexamethylene biguanide, chlorhexidine, and alexidine). These polymers are incorporated into the bacterial phospholipid bilayer which results in increased permeability. They also bind to bacterial DNA to alter transcription and they also inhibit respiratory enzymes. They have large sized molecules and a small percentage of patients show sensitivity.

Can be found by itself or in a dual status with quaternary ammonium compounds.

Question 24

Quaternary ammonium compounds - ... disinfection

These are cationic detergents that are effective against ... and .... ... (abbreviation) (causes .../... in some people) and .... They have ... size and approximately ...% of patients may show .... Disinfection is achieved in ... hours.

Active ingredient in OPTI-FREE ... and ... (which had increased risk of ... due to ... agent being removed) and OPTI-FREE ....

Can be found by itself or in a dual status with ... compounds.

Answer 24

Quaternary ammonium compounds - chemical disinfection

These are cationic detergents that are effective against bacteria and fungi. Benzalkonium chloride (BAK) (causes allergic/toxic responses in some people) and polyquaternium-1. They have large molecular size and approximately 1% of patients may show sensitivity. Disinfection is achieved in 6 hours.

Active ingredient in OPTI-FREE Express and RepleniSH (which had increased risk of infiltrative keratitis due to chelating agent being removed) and OPTI-FREE Puremoist.

Can be found by itself or in a dual status with biguanide compounds.

Question 25

Multipurpose solutions

Combine the actions of ..., ..., ..., .../..., and sometimes ....

Advantages: ..., ..., ..., ...

Disadvantage: ..., ..., MPS solutions can result in ... than H2O2 for Si-H lenses

Answer 25

Multipurpose solutions

Combine the actions of cleaning, rinsing, disinfection, storage/soaking, and sometimes enzymatic cleaning.

Advantages: convenience, reduced cost, eliminate saline, enhance compliance

Disadvantage: compromised efficacy?, solution toxicity/sensitivity, MPS solutions can result in significantly more corneal staining than H2O2 for Si-H lenses

Question 26

No rub solutions

Still required significant rinsing procedure, need to ..., prior to disinfection. Used with lenses worn .... ... is always better.

Answer 26

No rub solutions

Still required significant rinsing procedure, need to be in contact with fluid stream for 20secs, prior to disinfection. Used with lenses worn 30 days or less. Rubbing is always better.

Question 27

Fusarium keratitis - MPS

In 2006, a cluster of cases were reported from patients using ..., removed from market. Resulted in preservative being ... and patients weren’t ..., resulting in less ... effects and basically putting their contacts in ... each night.

Answer 27

Fusarium keratitis - MPS

In 2006, a cluster of cases were reported from patients using B&L Renu with Moistureloc, removed from market. Resulted in preservative being absorbed in to CL and patients weren’t replacing fluid in cases, resulting in less disinfective effects and basically putting their contacts in water each night.

Question 28

What lens care regime should be used for which lens type?

MPS adequate for ... lenses but recent studies suggest ... is better. Separate ... and ... recommended for lenses not replaced daily (research unclear).

Answer 28

What lens care regime should be used for which lens type?

MPS adequate for disposable Si-H lenses but recent studies suggest H2O2 is better. Separate daily cleaner and enzyme cleaning recommended for lenses not replaced daily (research unclear).

Question 29

Silicone hydrogels and care systems

These lenses have unique characteristics; ... to a lesser extent, absorb ..., increased ..., and reduced ... due to exposure of ... at material surface.
Different ... show varying effectiveness in reducing ... and ... accumulation in different lens ....

Answer 29

Silicone hydrogels and care systems

These lenses have unique characteristics; dehydrate to a lesser extent, absorb less protein, increased lipid deposition, and reduced wettability due to exposure of silicone groups at material surface.
Different lens solutions show varying effectiveness in reducing protein and lipid accumulation in different lens polymers.

Question 30

Preservatives and Si-H contact lenses
MPS solutions cause increased ... in Si-H lenses compared to ... lenses.

Answer 30

Preservatives and Si-H contact lenses
MPS solutions cause increased asymptomatic staining in Si-H lenses compared to hydrogel lenses.

Question 31

MPS and hypersensitivity reactions

Different preservatives give potential lid changes; ... > ... > .... Therefore, important to ....

Answer 31

MPS and hypersensitivity reactions

Different preservatives give potential lid changes; polyhexanide > polyquad > peroxide. Therefore, important to assess palpebral conjunctiva.

Question 32

Enzymatic/protein cleaning

Remove ... as ... of bound protein increases with .... Usually a tablet which is ... but also in liquid form. Can do this process ..., ..., or ..., depending on ..., ..., and .... Always have to ... and ... before enzymatic treatment. Less protein binding with ....

Answer 32

Enzymatic/protein cleaning

Remove bound insoluble protein as immunogenic potential of bound protein increases with contact age. Usually a tablet which is dissolved in MPS or H2O2 but also in liquid form. Can do this process daily, weekly, or fortnightly, depending on lens type, frequency of wear, and rate of deposition. Always have to surface clean and rinse before enzymatic treatment. Less protein binding with regularly replaced disposable lenses.

Question 33

Enzymatic/protein cleaning

Protein remover may contain: a ..., a combination of ... whose actions are specific to ... (... and ... for ...), and ... or ... which are not enzymes.

Maybe sources from ..., ... (usually derived from ...), or ....

Answer 33

Enzymatic/protein cleaning

Protein remover may contain: a protease, a combination of enzymes whose actions are specific to tear components (lipases and mylases for mucins), and inorganic chemicals or organic entities which are not enzymes.

Maybe sources from plants, animals (usually derived from pigs), or microorganisms.

Question 34

Case care

The major factors in reducing the levels of contact lens care contamination are: ..., using .../... to scrub with .../..., and then drying with ... before .... Should change cases every ... months.

Answer 34

Case care

The major factors in reducing the levels of contact lens care contamination are: wash hands with soap and water, using hot water/disinfecting solution to scrub with toothbrush/cotton bud, and then drying with lint free cloth before air drying face-down. Should change cases every 3 months.

Question 35

Antibacterial lens cases

CIBA Vision Microblock contains ... which is a .... Efficacy with ...hour soak and needs to be .... Showed reduced ... and ...; but no extra benefit against ... and ....

Answer 35

Antibacterial lens cases

CIBA Vision Microblock contains silver co-polymer which is a broad spectrum antibacterial, antifungal, and antiviral. Efficacy with 24hour soak and needs to be kept moist to maintain activity. Showed reduced pseudomonas and S. Marcescens; but no extra benefit against S. Aureus and C. Albicans.

Question 36

Rewetting/lubricating drops are used for ..., ... from eye/lens, ..., ... patients, ..., ..., and ... symptoms.

Can be ... or in ... and usually contain a ..., ..., and .... May contain a weak ... but is mostly .... ... drops are better given that patients will probably use these ... throughout the day (such as ...) but some drops have .... Need to make sure that drops are good for ... use.

Answer 36

Rewetting/lubricating drops are used for alleviating dryness/discomfort, flushing irritating particles from eye/lens, rehydrating lenses, marginal dry eye patients, dry environments/windy conditions, tired eyes, and mild allergy symptoms.

Can be preserved or in unit dose and usually contain a wetting agent, buffer system, and viscosity enhancing agent. May contain a weak surfactant but is mostly saline. Non-preservative drops are better given that patients will probably use these multiple times throughout the day (such as HyloForte) but some drops have preservatives. Need to make sure that drops are good for CL use.