Solutions Flashcards
Examples: Preservative/Disinfectants (2)
Polyhexanide
Peroxide
Purpose: Preservative/Disinfectants (3)
Restricts growth of micro-organisms
Maintains sterility
Breaks down cellular wall of bacteria (can also do to epithelium)
(failure to disinfect is major cause of microbial keratitis)
Examples: Chelating Agents (1)
Ethylene Diamine Tetra-acetic Acid (EDTA)
Purpose: Chelating Agents (3)
Enhances preservatives (especially against gram -ve bacteria)
Prevents bacterial growth (binds ions)
Reduces protein build up
Examples: Buffer (1)
Boric Acid
Purpose: Buffer (2)
Balances acid/alkaline concentration - stabilises pH
Average tear pH is 7.45 but buffer aims for 6.6-7.8
Example: Isotonic Agent (1)
Sodium chloride
Purpose: Isotonic Agent (4)
Maintains tonicity to match tears
About 0.9% sodium chloride
Too high tonicity = hyperaemia & dehydration
Too little tonicity = oedema
Examples: Viscosity Agent (1)
Polyvinyl Alcohol (PVA)
Purpose: Viscosity Agent (3)
Increases thickness
Increases contact time with lens
Found in artificial tears
Examples: Wetting Agents (1)
Polyvinyl Alcohol (PVA)
Purpose: Wetting Agents (2)
Conditioning
Reduces wetting angle = better spread of tears & solution across surface
Examples: Surfactants (1)
Polaxamine
Purpose: Surfactants (2)
Reduces surface tension
Easy removal of debris and pathogens
Example: Stabiliser (1)
Phosphonic Acid
Purpose: Stabiliser (1)
Maintains cohesion within a solution (can become unstable over time)
Examples: Enzymes (2)
EDTA
Aldox
Purpose: Enzymes (2)
Removes deposits
Breakdowns protein bonds
Current Preservatives: (3)
Polyquaternium
Polyhexanide
Polyquaternium-1
Peroxide
Polyquaternium (polyquats) (2)
Large molecule size does not penetrate soft lens material
Less toxic to ocular surface
Polyquaternium-1 (polyquads) (2)
Minimal toxicity
Less efficient against fungai - aldox included to aid this
Polyhexanide (dymed) (3)
Lighter than polyquads
Effective against bacteria
Risk of allergies with sensitive wearers
Pathogens (Example): Gram Positive Bacteria (1)
Staphylococcus Aureus
Pathogens (Presents): Gram Positive Bacteria (3)
Keratitis
Conjunctivitis
Blepharitis
Pathogens (Example): Gram Negative Bacteria (1)
Pseudomonas Aeruginosa
Pathogens (Presents): Gram Negative Bacteria (2)
Keratitis/Ulceration
Conjunctivitis
Pathogens (Example): Virus (2)
Herpes Simplex
HIV
Pathogens (Presents): Virus (2)
Keratitis/Ulceration
Conjunctivitis
Pathogens (Example): Fungi (1)
Candida Albicans
Pathogens (Presents): Fungi (1)
Keratitis/Ulceration
Pathogens (Example): Amoeba (1)
Acanthamoeba
Pathogens (Presents): Amoeba (1)
Keratitis/Ulceration
Five aims of a contact lens care system (5)
Non-toxic
Compatible
Effective
Simple
Affordable
Non Toxic:
Should not damage or irritate ocular surface
Compatible:
Should perform well with lens type it was designed for
Effective (3)
Remove deposits & build up
Decontaminate/disinfect the lens
Optimise vision & comfort
Simple
Easy to use and encourage compliance
Affordable
Avoid non-compliance and reuse/sparingly use solution
Reasons for solution compliance issues (6)
Cost
Convenience
Ignorance
Denial
Bad advice (from friends)
Lack of incstruction/forgetting
Peroxide (2)
Effective against bacteria and fungi
Low concentration used
