Eye (year 2)

Question 1

what do topical drugs have to cross to penetrate the eye?

Answer 1

cornea, conjunctiva, sclera

Question 2

what are the advantages of topical administration?

Answer 2

specific
minimal side effects
easy
convenient

Question 3

what are the advantages of systemic delivery?

Answer 3

better for posterior segment

easier in fractious animals

Question 4

where may a drug be distributed when delivered topically to the eye?

Answer 4

into the eye
drain into lacrimal duct
enter systemic circulation through nasal mucosa/conjunctiva
fall off eye

Question 5

why must a gap be left when administered two drops of different topical drugs to the eye?

Answer 5

eye can only hold half a drop so if both applied the efficacy will be reduced

Question 6

what ways can topical ocular drugs be improved?

Answer 6

increase retention time

optimise ability to penetrate cornea

Question 7

retention time of a drug depends on the formulation, name these from shortest to longest retention time

Answer 7

solution
suspension
ointment
viscous gel
colloidal system
solid delivery
sub-conjunctival injection

Question 8

what does corneal penetration of the drug depend on?

Answer 8

solubility

Question 9

what does corneal epithelium have that limits paracellular absorption?

Answer 9

tight junction

Question 10

what route do lipid soluble drugs take through tissue?

Answer 10

trancellular

Question 11

what route do water soluble drugs take through tissue?

Answer 11

paracellular

Question 12

what part of the eye do water soluble agents easily cross?

Answer 12

stroma

Question 13

what part of the eye do lipid soluble agents easily cross?

Answer 13

epithelium

Question 14

what does a drug need to penetrate the cornea?

Answer 14

both hydrophilic and lipophilic characteristics

Question 15

what effects the water and lipid solubility of a dug?

Answer 15

its ionisation

Question 16

ophthalmic drugs have what type of pH?

Answer 16

weak acids or bases so have both ionised and unionised forms

Question 17

is the ionised portion of the drugs water or lipid soluble?

Answer 17

water

Question 18

is the unionised portion of the drugs water or lipid soluble?

Answer 18

lipid

Question 19

describe the ionisation as ocular drugs move through the cornea?

Answer 19

unionised form moves through corneal epithelium with ease, it then ionises due to the abundance of unionised drug allowing it to move through the stroma, it then becomes unionised again to pass through the endothelium

Question 20

what clinical factor may increase the absorption of topical ocular drugs?

Answer 20

corneal ulcers mean increased penetration for water soluble drugs

Question 21

how can large hydrophilic molecules be absorbed into the eye?

Answer 21

via conjunctiva and sclera as they permit more paracellular movement

Question 22

where can drugs enter from the sclera?

Answer 22

posterior segment

ciliary body

Question 23

how is much of the topically administered drug absorbed systemically?

Answer 23

via the nasolacrimal duct

Question 24

do topical drugs that penetrate via a non-corneal route have higher levels in anterior uvea or aqueous humour?

Answer 24

anterior uvea as they don’t pass through the aqueous humour to reach it but instead go through the ciliary body

Question 25

what does the blood:ocular barrier consist of?

Answer 25

blood:aqueous and blood:retinal barriers

Question 26

what is the blood:aqeuous barrier?

Answer 26

barrier between the blood in the vessels of iris/ciliary body and aqueous humour

Question 27

what is the blood:retinal barrier?

Answer 27

barrier retinal pigment epithelium and the retinal capillary endothelium

Question 28

why may pupil size want/need to be altered?

Answer 28

dilate for fundic exam relax ciliary body to relieve spasms constrict to open drainage angle diagnostic tool

Question 29

what is the term used for pupil dilation?

Answer 29

mydriasis

Question 30

what is the term used for pupil constriction?

Answer 30

miosis

Question 31

what is the term used to describe relaxation/paralysis of the ciliary body?

Answer 31

cycloplegia

Question 32

what is a two groups of drugs that cause mydriasis?

Answer 32

parasympatholytics | sympathomimetics

Question 33

what do parasympatholytics do to the eye?

Answer 33

relax the iris sphincter muscle to cause dilation

Question 34

what do sympathomimetics do to the eye?

Answer 34

contact the dilator muscle to cause pupil dilation

Question 35

name two parasympatholytics that cause mydriasis

Answer 35

atropine and tropicamide

Question 36

name a sympathomimetic that causes mydriasis

Answer 36

phenylephrine

Question 37

describe the pharmacokinetics of atropine?

Answer 37

slow onset but a very long duration of action

Question 38

when is tropicamide used and why?

Answer 38

during pupil dilation exam due to its rapid onset and short duration of action

Question 39

what are the three components of tear film?

Answer 39

lipid, aqueous and mucin

Question 40

name two drugs that stimulate tear production

Answer 40

ciclosporin and pilocarpine

Question 41

what is ciclosporin used for?

Answer 41

directly stimulate tear production and addresses underlying immune mediated cause as it is an immunosuppressant

Question 42

what type of drug is pilocarpine?

Answer 42

parasympathomimetic

Question 43

what are the categories tear substitutes fall into?

Answer 43

aqueous substitutes mucin replacements lipid replacements

Question 44

give an example of a mucin replacement

Answer 44

carbomer gel

Question 45

what type of acid is a good mucin replacer?

Answer 45

hyaluronic

Question 46

what are lipid replacements used for?

Answer 46

increase tear retention time

Question 47

what is glaucoma?

Answer 47

sustained increase in intraocular pressure

Question 48

what can glaucoma cause?

Answer 48

pain, blindness, irreversible structure changes

Question 49

what is glaucoma usually due to?

Answer 49

decreased aqueous humour outflow

Question 50

what are the aims of glaucoma treatment?

Answer 50

increase aqueous humour outflow decrease aqueous humour production both

Question 51

what drugs can be used in acute first line treatment of glaucoma?

Answer 51

osmotic diuretics

Question 52

what do osmotic diuretics require to work?

Answer 52

intact blood:ocular barrier

Question 53

how do osmotic diuretics work?

Answer 53

increase blood tonicity causing water to be drawn out of the aqueous humour

Question 54

name the groups of drugs that can be used to treat glaucoma

Answer 54

carbonic anhydrase inhibitors prostaglandin analogues beta blockers parasympathomimetics

Question 55

how do carbonic anhydrase inhibitors work?

Answer 55

reduce the formation of bicarbonate in the ciliary body epithelium which reduces the blood drawn into the aqueous humour

Question 56

how are carbonic anhydrase inhibitors administered?

Answer 56

topically

Question 57

how do prostaglandin analogues work to treat glaucoma?

Answer 57

increase the outflow of aqueous humour by increasing uveoscleral outflow by altering the structure of the outflow tract

Question 58

prostaglandin analogues are thought to also preserve vision in glaucoma patients, how?

Answer 58

increase perfusion of optic nerve head by vasodilation

Question 59

what is an adverse effect of prostaglandin analogues?

Answer 59

can be irritants

Question 60

give an example of a beta blocker used to treat glaucoma

Answer 60

betaxolol - topical beta1 antagonist

Question 61

how do parasympatheticomimetics work to treat glaucoma patients?

Answer 61

contact ciliary body to constrict the pupil and open the drainage angle to increase the outflow of aqueous humour

Question 62

name a parasympatheticomimetics used to treat glaucoma

Answer 62

pilocarpine

Question 63

what do parasympatheticomimetics rely on to work in glaucoma patients?

Answer 63

an intact drainage angle