Sensitivity is lost in the following receptus - smallest axons first. List them in order.
Pain
Touch
Temperature
Pressure
How do local anaesthetics work? The mechanism?
Corneal nerves are un-myelinated, therefore they are transparent
What makes a good local anaesthetic
When do optoms use local anaesthetics?
Applanation tonometry
Gonioscopy
FB removal
CL fittings
Local ocular anaesthetics come in 2 types. What differentiates them in terms of structure? Give names of them.
**ALL DRUGS ARE POM - used by optoms but not for supply
Ester linkage
unstable - likely to cause allergic rns
Short action
Metabolised by plasma
Amide linkage
Metabolised by liver
Long acting
Tetracaine HCL ( Amethocaine)
stings on instillation
deepest level of anaesthesia
least common anaesthetic
contraindications with pxs taking sulphonamides( antibacterials) for sysemic diseases
RARE rns: allergic conjunctivitis, blurry vision
0.5% + 1.0% strength Minims
1 min onset
used for FB removal
Oxybuprocaine HCL (Benoxinate)
stings less than Tetra
has some bactericidal properties
very commonly used by optoms
0.4% strength Minims
1/2 drops
onet is 1min
used for applan tono + FB removal
Proxymetacaine HCL
minimal stinging
least anti-bacterial properties ( useful when taking conjunctival swabs)
commonly used by optoms
caution w/ allergies, heart dieases, hyper thyroidism
0.5% strength Minims
store in fridge ( out for 1 month)
13sec onset
Lidocaine HCL ( Lignocaine)
provides longer duration
less commonly used
4% strength Minims with NaFl
onset = 1min
What are the precautions that need to be taken with local ocular anaesthetics
What should optoms do before and after administrating anaesthesia
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