Topical Anaesthetics Flashcards
Why are disposable tips used for tonometry
Risk of variant creutzfeld- Jacob disease. VCJD- rare neurogenic disease.
What are topical anaesthetics used for ?
Applanation tonometry
Gonioscopy
Ultrasound- Pachymetry
Removal of FB
Cyclopegia
Contact lenses- RGP
Also other uses like lacrimal patency procedures
Before testing tbut so u get accurate reading
When u need a Px to not blink for an investigation
However DONT use to manage ocular sx and avoid in pre term neoates
Can reusable tips be used. What’s the conditions??
Yes they can be. But must be sterilised in a special way. Six step method- but be sure it doesn’t dry and have spares on hand
- Rinse in saline for 30 seconds
- Clean surfaces with soap then rinse with saline for 30seconds
- SOAK IN 1% Hypochlorite for 10mins
- Rinse in 3 changes of saline. For 10mins
- Shake, dry and store in suitable container
- conventional disinfection to follow
Why would u use a topical anaesthetic for cl
For RGPs
For scleral fitting- haptic fitting
Why’s topical anaesthetic used with Cyclopegia
To enhance time and depth of Cyclopegia. And to assist Mydriatics espesh in those Px with highly pigmented iris
How does a topical aneasthetic work?
The nerve cell mambrane- lipoidal- normally allows cations through channels. However cation region on TA bind to the phospholipid layer and block the Na channel. Therefore No axon depolarisation as prevents voltage dependant increase in Na+
What is the time course for anaesthetics
In general onset of 1 min. But could be 30secs.
Recovery of approx 20-30mins. But however again varies. Proxy and oxy- 15mins. Tetra- 20 mins. And lydo- 30mins
How would u asses recovery of a topical aneasthetic
With a silver of tissue. Even Kleenex med wipe
Adverse reaction of topical aneasthetics include:
Corneal desquamation- check integrity More susceptible to FB Reduced tear film Reduced uptake of oxygen. So mitosis and cell migration inhibited Reduce in IOP Increase in corneal thickness Tinnitus Increase permeability of cornea Mild hyperaemia Reduced blink reflex Transient superficial corneal erosion Stings
Which topical aneasthetic causes more risk of a hypersensitivity reaction
Those with an ester linkage
Ie. Proxy oxy and tetra
Not those with amide linkage like lidocaine
Tell me about proxymetacine
Most commonly used Well tolerated Stings less Similar characteristics of tetra and oxy Store in refrigerator-2-8degrees Available in minims
0.5%
POM
Estér bond
So oxybuprocaine. How u doing. Feeling left out bc proxymetacine took ur space?
Ester linkage Stings Available in minims 0.4% POM
Tetracine
Available 0.5 and 1% Minims Is an ester bond Not used generally Maybe before surgery
Lidocaine
Amide bond 4% but not available alone. Just with fl Used in surgery Preferred in reaction with other TA Longer onset. Shorter duration Stings
