CL - Efficacy Of CL Solutions - Week -3 Flashcards
What are the 4 testing criteria for CL solutions?
Sterility
Preservative effectiveness
Microbial limits test (tablets/dry products only)
Stability
What test must a CL solution pass to be labelled a “disinfecting solution”?
The Stand Alone Test
What must a MPS (multipurpose solution) pass to meet criteria as both a daily cleaner and disinfectant?
Regimen test
Describe the pathway of testing for CL solution standards (2)
- Does it pass stand alone?
- If not, does it work as a regime?
What microorganisms is a CL solution tasked with dealing with in a stand alone test? (5)
Gram +ve cocci: staph aureus
Gram -ve rod: Serratia meracellens
Gram -ve myo: ps aeruginosa
Yeast: Candida albicans
Fungus: fusarium salani
When is the extent of visibility loss of microorganisms determined in the stand alone test?
At 25%, 50%, 75%, 100% of MRDT (minimum recommended disinfectant time)
What is the pass criteria for a disinfecting CL solution in a stand alone test? (2)
Bacteria reduction by 3 log units (99.9%) within MRDT
Mould and yeast reduction by 1 log unit (90%) within MRDT (+ no increase within 4xMRDT)
What does the Regimen test evaluate?
The antimicrobial efficacy of the entire regimen described in the cleaning instructions insert (i.e. rub, rinse, soak)
What is the pass criteria for the Regimen test (2)?
Bacteria: sum of averages is 5.0log reduction for bacteria with minimum of 1.0 log reduction at MRDT
Moulds and yeast: stasis over MRDT
List 6 disadvantages for the stand alone test
Limited # bacteria tested
No acanthomoeba
No viruses
Lab strains, not clinical isolates
Organic matter (eg mucus, tear debris) not accounted for
Sterile lab env = not the real thing
What is the most common type of microorganism to contaminate a lens solution/ case? What other kinds of microorganisms can contaminate?
Most common = gram +ve bacteria
Gram -ve (also common)
Fungi/yeasts (20-40%)
Acanthomoeba (up to 9%)
What is the main difference between chlorhexidine and polyhexadine?
Polyhexadine has a larger molecular weight than chlorhexidine, which means that it is not able to enter the matrix of soft lens materials and this reduces the likelihood of preservatives reaching the ocular surface
i.e. polyhexadine doesn’t enter the lens b/c of it’s MW
What micororganism persists even after disinfection with chlorhexidine?
s. marcescens
Can acanthomoeba survive in 1-step 3% hydrogen peroxide systems? Explain
yes. Because the neutralisation of the peroxide is too rapid.
What disinfectant is the best at killing microorganisms?
Hydrogen peroxide
What percentage of microorganisms on CLs are lost through rinsing? What about rinsing and rubbing together?
Rinsing: 99%
Rinsing and Rubbing: 99.9%
Is Acanthamoeba included in FDA/ISO challenge testing?
no
What do acanthamoeba feed off of?
gram negative bacterial biofilms that form on CL cases
How can you kill acanthamoeba cysts and trophozoites on CL cases?
Scrub CL case well + very hot water (>70deg) [scrubbing will remove the biofilm]
Why shouldn’t you leave your CLs in hydrogen peroxide for extended periods of time (like a fortnight for example)? How long should you leave them in before replacing solution?
The hydrogen peroxide systems wear off over time, resulting in the CL eventually sitting in saline for most of the time. This is a problem because micro-organisms can regrow over time. Should change solution if it’s been longer than a week.
How does the incidence of contamination compare for EW vs daily CLs?
Higher incidence in EW for contamination of case, solution, and CLs
When may CL contamination in EW Si-H lenses become more likely? And by how much?
2.5x more likely in the presence of substantial lid and/lr conjunctival bioburden (e.g. capped glands, bleph)
What lifestyle factors can influence CL contamination? (2)
Swimming, especially with goggles (increased pool bacteria, S. epidermidis)
Navy environment (higher incidence of enterobacter and pseudomonas)
Would you suggest EW CLs for a person on ships in the navy?
No. Contraindicated. (due to the higher incidence of enterobactor and pseudomonas)
How might corneal inflammation affect CL contamination? (2)
CL colonisation by gram -ve
Eyelid colonisation by s. aureus
How might corneal infection affect CL contamination? (3)
Most commonly: p. aeruginosa, s. marcescens, acanthamoeba sp.
Give 4 examples of poor compliance from CL wearers
Hand washing
Case hygeine
Inadequate cleaning (omission of rub step)
Infrequent/no disinfection
What is poor compliance of CL care a risk factor for?
microbial keratitis
How does the use of tap water contribute to CL contamination?
significantly increases contamination by especially gram -ve bacteria
What does failure to air-dry the CL case increase the risk of? What about infrequent replacement:
6.4x higher risk of microbial keratitis
5.4x higher risk of microbial keratitis
What are the two types of P. aeurignosa strains and which is more resistant to disinfection?
Invasive: invade corneal cells and don’t kill cells
Cytotoxic: remain extracellular and kill the cells. These are the more resistant one
What patient factors impact choice of CL cleaning solution? (3)
Cost, Convenience, Complexity - the three C’s
What patient complications may impact choice of CL cleaning solution? (2)
Hypersensitivity (this is why you always assess palpebral conj)
Comfort
How does peroxide compare with multipurpose solutions? (6)
More complex?
More expensive
Less frequently available
Continuous disfinection
Stinging (need to neutralise or it will hurt)
Effect on deposits?
How does the duration of comfortable wearing time of CLs compare with peroxide vs polyquad? (in Si-Hys, air optix and oasys)
peroxide resulted in longer reported comfortable wearing times (11hrs vs 9hrs on average) (p<0.05) (Keir et al. 2010)
How does hydrogen peroxide compare with mps in terms of corneal health?
Hydrogen peroxide had significantly lower rate of CIEs (corneal infiltrate events) and SICS (solution induced corneal staining)
How is SICS defined?
diffuse punctate staining (grade 1+) in at least 4 of the 5 cornealregions (central, superior, inferior, nasal, temporal)
How long can lenses be stored for until re-disinfection is required?
7 days
How frequently should you replace:
MPS
Hydrogen Peroxide
Saline
Lubricant drops
MPS: 3 months
Hydrogen peroxide: 100 uses or 3 months
Saline: 14 days
Lubricant drops: 1-6 months depending on preservatives
How frequently should you replace your CL case?
every 3 months
