CLM - Soft Contact Lens Maintenance - Week 8 Flashcards
List 6 key requirements for contact lens solutions.
Antimicrobial efficacy
Non-toic to ocular tissue
Minimum effect on lens parameters
Simple to use
Convenient
Inexpensive
List 7 possible components of a contact lens solution.
Water
Osmolarity adjusting agents
Buffering agents
Surfactants
Preservatives/disinfectants
Chelating agents
Viscosity enhancing agents
Give an example of an osmolarity adjusting agent and an ideal percentage. What else can it be used for?
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)
What is a buffer solution and what doth it do?
A combination of weak acids or bases and their salts
This stabilises and maintains preferred solution pH under varying conditions
What determines the buffer and final pH to be used in a contact lens solution?
The preservative type
List the 5 components of lens care routine.
Handwashing
Surface cleaning
Rinsing
Disinfection
Enzymatic cleaning
Case care
When handwashing, what should be avoided?
Soaps with added moisturisers/perfumes/scents etc
What is the most important step in lens care routine?
Surface cleaning
What log unit reduction in microorganisms occurs with surface cleaning?
2-4 log unit reduction, up to 99.9% removal
Whats more important, the cleaning process of a lens or the brand of cleaner used?
Cleaning process
When must surface cleaning be done?
Every time the lenses are taken off.
What is surface cleaning typically conducted with?
Multipurpose solutions, but daily cleaners are available
What is the purpose of rinsing after surface cleaning?
Flush loosened debris and remove cleaner
What occurs with disinfection? Is sterilisation achieved?
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
What is the mosr common form of contact lens disinfection? How is microbial death achieved (2)?
Chemical disinfection
Dissolves cell membrane lipids
Denatures proteins essential for function
List 4 physical methods for soft contact lens disinfection. Is this common?
Thermal
Microwave
Ultraviolet
Ultrasound
Rare now
List 5 types of chemical methods for soft contact lens disinfection.
Biguanides
Quaternary ammonium compounds
Hydrogen peroxide
Sorbic acid
Thimerosal (autistic screeching)
What is an advantage of disinfection using microwaves?
Effective and rapid elimination of bacteria via inhibition of metabolism
What are 4 disadvantages of disinfection using microwaves?
Long term effect on lens polymers could be damaging
Difference in microwave brands/outputs etc
Initial cost of the microwave
Lack of portability
Describe hydrogen peroxide as a disinfectant.
Strong oxidising agent at 3%
Toxic to the eye and requires inactivation using a tablet or liquid or platinum
What is the minimum soaking time in hydrogen peroxide before neutralising? What is recommended?
Minimum 3 hours
6 hours recommended (overnight)
List 4 advantages of hydrogen peroxide for contact lens disinfection.
Preservative free
Broad antimicrobial efficacy
Creat for conventional soft lenses
Less staining than chemical solutions for SiH lenses
List 4 disadvantages of hydrogen peroxide for contact lens disinfection.
Residual peroxide may cause discomfort and hyperaemia
Little to no ongoing disinfection capability
Expensive
More difficult/lower compliance (not with the one step system)
List two old generation disinfectants and why they are classed so. What to new generation disinfectants have that prevents this?
Chlorhexidine and thimerosal
Due to uptake into the lens matrix
Newer generation disinfectants have larger molecules, minimising absorption
