7 - Anasthetics and stains

Question 1

what is a topical anaesthetic

Answer 1

POM
- drugs that reversibly block transmission in sensory nerves

Question 2

indications for use ?

Answer 2

• contact tonometry
• cl fitting
• foreign body removal
• gonioscopy
• lacrimal procedures
• ever for release of symotoms

Question 3

advantages of local anaesthetics

Answer 3

• allow certain procedures to be conducted
• make px more comfortable
• makes procedure easier for practitioner

Question 4

disadvantages of local anaesthetic

Answer 4

• sting (due to pH)
• delay healing (reduces production of collagen)
• eye is more susceptible to damage

Question 5

what is the mode of action of local anaesthetics

Answer 5

memorise action potential graph + process

• action potential passes along nerve
• successive depolarisations and repolarisations of adjacent areas

topical anaesthetics reversibly block nerve conduction by blocking sodium channels, therefore action potential cannot be generated

Question 6

what are local anaethetics made of

Answer 6

lipid soluble hydrophobic portion
and a readily ionised hydrophillic portion

they can swtich from charged and unchargedh

Question 7

what does being hydrophobic and lipophillic allow them to to

Answer 7

rapidly diffuse across lipid membrane of the epithelial cells and bind to the intracellular portion of sodium channels

Question 8

what are the different portions separated by

Answer 8

• intermediate alkyl change

which contains either an ester or amide linkage

Question 9

chemical structure of anesthetics
ESTER LINK

Answer 9

• hydrolysed by cholinesterase
• short duration
• oxybuprocaine
• tetracaine
• proparacaine

Question 10

chemical structure of local anaesthetics
AMIDE LINK

Answer 10

• resistant to hydrolysation
• longer duration

Lignocaine only

Question 11

which structure are allergic reactions more common in

Answer 11

esters

Question 12

which linkage bond is broke more easily

Answer 12

ester

Question 13

what is the onset of all anaesthetics

Answer 13

1 min

Question 14

15 mins duration

Answer 14

• oxybuprocaine
• proxymetacaine

Question 15

20 mins duration

Answer 15

tetracaine

Question 16

30 min duration

Answer 16

lidocaine

Question 17

which anaesthetic is most potent

Answer 17

tetracaine hydrochlride (amethocaine)

stings most

• provides deepest anaesthesia
• foreign body removal

sensitivity is rare but occurs after repeated doses

• associated with punctate staining

Question 18

contraindications/caution of tetracaine hcl

Answer 18

• prematue babies
  -known allergy
• sulphonomides
• prenancy/lactation

Question 19

preparations of tetracaine hcl

Answer 19

0.5% and 1% in minims

• store below 25 and protect from light
• hydrolysed by light
• solutions >1% damage cornea

removal of foregin body after 1 drop

Question 20

which is most commonly used by optoms

Answer 20

oxybuprocaine hydrochloride (benoxinate)

• less stinging and irritation than amethocaine
• bactericidal properties (disadvantage)

Question 21

what are contraindications/cautions of oxybuprocaine

Answer 21

• known allergy
• premature babies
• pregnancy/lactation
• if px is on any other drops containing chlorohexidine acetate as a preservative are being used

Question 22

preparations of oxybuprocaine hcl

Answer 22

• minims 0.4%
• store below 25 protect from light

opthalmology
- 3 drops over 5 min interval allows foreign body to be removed

Question 23

which one stings least

Answer 23

Proxymetacaine HCL
- ideal for tonometry, minimal punctate corneal staining
- least antibacterial properties

Question 24

contraindications/caution of proxymetacine hcl

Answer 24

• known allergy
• overactive thyroid
• heart disease
• premature babies
• pregnancy/lactation

Question 25

preparations of proxymetacine hcl

Answer 25

minims 0.5%
stored 2-8C, fridge

can be used in cataract extraction as vert potent

Question 26

Lidocaine HCL (lignocaine

Answer 26

• stings less than amethocaine
  -amide link - used if px sensitive to ester link
• longer duration

contraindications/caution
- pregnancy/ lactation
- premature babies

Question 27

lidocaine hcl preparations

Answer 27

• minims 4% combined with 0.25% fluoroscien

Question 28

side effects of lidocaine

Answer 28

• transient stinging/bluring
• conjunctical hyperaemia
• mild superficial epithelial damage
• ## punctate keratitis

repeated use ~ epithelial toxicity ~ serios keratopathy

Question 29

uses + disadvantages of Fluoeoscien

Answer 29

• tonometry
• corneal abrasions
• CL fitting
• TBUT
• lacrimal drainage

psuedomonas aeruginosa

Question 30

rose bengal uses + disadvantages

Answer 30

• staining od fead and devitalised cells
  -aids dry eye diagnosis

irritates try eyes on instilation
stings
can stain healthy cells

Question 31

uses and disadv of lissamne green

Answer 31

• stains lipid like structures

no disadvantages

Question 32

why is fluoro not a true stain

Answer 32

just colours tear film.

epithelial damage means fluoro can gain access to deeper layers

Question 33

contrainidications of fluoro

Answer 33

• known sensitivity
• soft CL lenses

Question 34

cautions of fluoro in a multi dose bottle

Answer 34

-contamination problems in hospitals in 1950s
- fl used on damaged corneas
- psuedomonas has affinity for it
progesses rapidly
corneal perforation 48h

Question 35

fluoro minims

Answer 35

1 and 2%
contains buffer to stabilise solution
slighty alkaline