Week 11 - SCL Care Flashcards
Why do we bother with lens hygiene?
• reduce the number of microorganisms that accumulate on the lenses with wear
• minimise the risk of infection with contact lenses
• cleaning solutions can also improve comfort by conditioning and wetting the lens surface
What challenges do CL solutions face before being approved for use?
• Tested for ability to protect vs organisms:
- Pseudomonas (lens associated keratitis)
- Serratia (nun-ulcerising keratitis and endopthalmitis)
- Staphylococcus (microbrial keratitis - 25%)
- Candida (yeast infections)
- Fusarium (common fungus in 1st world)
What other challenges do CL solutions face?
• MRSA (methicillin-resistant Staphylcoccus aureus) - CL solutions have varying degrees of efficacy
• Acanthomoeba (amoeba) - found in tap water, very stubborn to kill in their cyst form. CL solutions have varying degrees of efficacy. Good compliance helps!
What 5 things must all solutions have in common?
• Sterile, stable at room temperature
• Harmless (relatively) to eye if accidentally instilled
• Have no adverse effects on contact lens materials
• Compatible with any other solutions
• Self-sterilising
What 3 steps are there to cleaning SCLs?
- Cleaning
- Rinsing
- Disinfecting / Storage
What is cleaning specifically?
• To clean debris from the lens
• To reduce deposit build up
• Important to include a lens “rub” step in cleaning regime to mechanically remove debris and deposits (oils, proteins,
“biofilm”)
What are the lenses cleaned with?
• Surfactant (surface-acting agent): poloxamer
• Hydrophilic and hydrophobic ends in molecule
• Hydrophobic interacts with debris to form micelles, hydrophilic reacts with water
• Effective against lipids and inorganic deposits
• Enhances lens wettability
What is rinsing?
• To clear the debris away that has been dislodged by the cleaning
• Prior to disinfection
• This can be done with MPS (multi-purpose solution) or sterile saline
Why is Disinfecting taken place, how is it done?
• Neutralise all microbes present on CL
• Different disinfectants take different lengths of time: check label
• Typically done overnight (once a week for EW)
• Refers to keeping solution in bottle safe, not just lenses
What are the 3 terms associated with antimicrobials, and their definitions?
- Sterilisation: the solution is sterile: BUT the solution does not sterilise lenses.
- Preservation: the preservatives present in the solution that prevent growth of micro-organisms in the bottle.
- Disinfection: the reduction of the level of micro-organisms to a level that is safe for the ocular surface without damaging the contact lens. This occurs in the contact lens case.
What are some examples if Biocides used in CL solutions?
• PHMB
• PAMB
• PQ-1
• MAPD
What are Multi-purpose solutions (MPS)
• The most convenient and common design
• Used for cleaning, rinsing and disinfecting
• Research showed apart for some fungal isolates, MPSs performed adequately (99.9% viability reduction) on FDA test-panel organisms
• Most CL companies have MPS options
- So do some of high street companies
MPS Steps - Bausch and Lomb example…
• Place 3 drops of MPS each side of lens, rub for 20s
• Rinse each side 5s with MPS
• Place cleaned lens in case, fill with fresh fluid at least 4hrs - discard solution from case after each use
What is the Hydrogen Peroxide CL system?
• Very different from MPS
• Hydrogen peroxide has broad antimicrobial activity - 3% concentration
• Destroys pathogens by oxidation, by denaturing protein; damaging membranes
• Preservative free!
• Requires catalyst to neutralise hydrogen peroxide, turning to water
• Disinfection takes 6hrs overnight
What are the 7 steps for REMOVING lenses with hydrogen peroxide?
- BEFORE handling your contact lenses wash, rinse, and dry hands
- Remove R lens and place into R basket, Carefully close the basket. Repeat for left eye.
- Rinse each eye in lens holder for 5s with peroxide
- Fill lens case up with peroxide solution
- Place lens holder in case, close cap securely. Solution will bubble.
- Allow 6hrs to soak, do not shake/turn upside down the case
What are the 4 steps for inserting lenses with hydrogen peroxide?
- BEFORE handling your contact lenses wash, rinse, and dry hands
- When 6hrs pass, open cap and take out lens holder
- Lenses can be rinsed with sterile saline prior to insertion
- After applying your lenses onto the eyes, discard all used, remaining one step peroxide solution from lens case, and leave it open to air dry
( If lenses stored for more than 1 day, will require disinfection)
What happens if Hydrogen peroxide not left to neutralise?
- Stinging
- Burning
- Corneal damage
How is the CL case cared for MPS?
• When the lenses removed, the case should be emptied of the current solution
• The case should then be rinsed out with the MPS solution or saline (not water)
• Make sure no residual lens solution is allowed to dry on the case, shake the lens case after rinsing
• Then the lens container and the lids should be left to air dry face down on a clean tissue before the lid is put back on (no towels)
• The lens case should be replaced ideally every month
How is the CL case cared for hydrogen peroxide?
• Once lenses are removed from the baskets, discard any remaining solution from the lens case
• Rinse the case with the peroxide solution or saline over a sink/basin
• Leave the lid off the case to air dry
What are the additives in solutions: Preservative and viscosity enhancers??
• Preservatives - maintain sterility of solution.
- BAK, PAPB etc
• Viscosity enhancers - thicken the solution
- PVA, methyl cellulose etc
What are the additives in solutions: Tonicity adjusters and Buffers?
• Tonicity Adjusters: to maintain the ideal contact lens salt solution of 0.9% sodium chloride. Too low and the cornea may swell, too high and it may dry.
- NaCI (sodium chloride)
- KCI (potassium chloride)
• Buffers - to stabilise the pH between 7.0 and 7.4
• Borate, Phosphate, Bicarbonate
What are the additives in solutions: Chelating agents, colouring agents, mild abrasives and sterile water/saline?
• Chelating agents - prevents lens deposits (binds free ions such as calcium and magnesium) & increases disinfectant antimicrobial activity
• Colouring agents; very rare modern day
• Mild abrasives: enhance the mechanical stripping of debris and proteins from lens surface (i.e polymeric beads)
• Sterile Water/Saline
Can patients have allergies to CL solutions and what can be done?
• Patients can be allergic to their CL solution
• Presents in the same way as most ocular allergies - itching, lacrimation, hyperaemia and peri-ocular swelling
• Usually this is due to the preservatives
• So what can we do?
- Temporarily discontinue lens wear
- There are “gentle” solutions that are marketed for sensitive eyes
- Hydrogen peroxide cleaning system
- Daily disposable lenses
What are Re-Wetting drops used for?
• Not part of every CL wearer’s care routine
• Often used in those who have CL-related discomfort (ocular pathology ruled out)
• Always consider a refit if it is in the patient’s best interests
• Re-wetting drops will give temporary relief
• Drain from the ocular surface quickly
• They attempt to mimic the natural tears that have evaporated quickly due to the presence of the CL
What are common ingredients for Re-Wetting drops?
• Sodium Hyaluronate
• Sodium chloride (saline)
• Povidone
• Hypromellose (hydroxypropyl methylcellulose)
• Carboxymethy|cellulose
What are Deposits and what are their effects?
• Protein, lipids, mucins, polysaccharides can build up on lenses
• More common when lenses are replaced less regularly
• Increase irritation, bacterial binding, potential for infection and incidence of CLPC
• Decrease comfort, decrease visual acuity, decrease CL life
What substances might a soft CL protein removal solution contain and their use schedule?
• Papain - protease that binds to CL materials (plant material)
• Pancreatin - protease, lipase (porcine)
• Subtilisin A or Subtilisin B - protease derived from bacteria
• Frequency of remover depends on how quickly build up appears
What steps are done before disinfection, regarding deposits?
• BEFORE DISINFECTION: Lenses soaked in MPS or saline with enzyme dissolved in solution - 15 min to overnight (depends on manufacturer’s recommendation)
• CLs should be rubbed & rinsed thoroughly in MPS or sterile saline after protein treatment
• Usually protein removal needs to be followed by disinfection
What steps are done during disinfection, regarding deposits?
• DURING DISINFECTION: Protein remover tablet placed in peroxide after case is filled but before the CLs immersed or neutralising tablet added
• Processing time is governed by the peroxide system’s disinfection
recommendations
• Lenses should be rubbed and rinsed thoroughly with fresh sterile saline after protein treatment immediately before lens insertion
What are some common mistakes in SCL care?
• Not rubbing the lenses
• “Topping up” contact lens solution
• Not changing CL case each month
• Tap water being used for any part of the care regime
• No hand washing
• Not leaving the solution the correct length of time for disinfection
• Using the incorrect solution
• Using expired solution
