3: Pharmacology

Question 1

How are drugs administered in ophthalmology?

Answer 1

Topically

Question 2

Hydrophilic drugs cannot pass through the ___.

Hydrophobic drugs cannot pass through the ___.

Answer 2

epithelium because they’re not lipid-soluble

stroma because they’re not water-soluble

Question 3

The epithelium of the cornea is ___.

The stroma of the cornea is ___.

The endothelium of the cornea is ___.

(hydrophilic / hydrophobic)

Answer 3

hydrophobic

hydrophilic

hydrophobic

like a big water sandwich

Question 4

Which drugs can pass through the epithelium?

Which drugs can pass through the stroma?

Answer 4

Hydrophobic i.e lipid-soluble

Hydrophilic i.e water-soluble

lipid : water : lipid

Question 5

Which type of drug easily penetrates the hydrophobic epithelium of the cornea?

Answer 5

Hydrophobic

i.e lipid-soluble drugs

Question 6

Which type of drug easily penetrates the hydrophilic stroma of the cornea?

Answer 6

Hydrophilic

i.e water-soluble

Question 7

Which topical antibiotic has both hydrophobic and hydrophilic properties?

Answer 7

Chloramphenicol

so it can pass straight through epithelium AND stroma

Question 8

How are steroids made more hydrophobic?

What layer does this let them pass through?

Answer 8

ALCOHOL or ACETATE

Epithelium

Question 9

How are steroids made more hydrophilic?

Which layer does this let them pass through?

Answer 9

PHOSPHATE

Stroma

Question 10

What is added to topical drugs to act as a preservative?

Answer 10

Benzalkonium

Question 11

How are topical eye drugs absorbed into the systemic circulation?

Answer 11

Inferior lacrimal papillae > Punctua > etc

Question 12

Apart from topically, how else are eye drugs administered?

Answer 12

Subconjunctival injection

Subtenons (a surface under the conjunctiva)

Intravitreal (into the posterior chamber through the side)

Intracameral (into the front of the eye)

Question 13

How are eye infections treated?

Answer 13

Topical antibiotics

Topical antivirals

Question 14

How is eye inflammation treated?

Answer 14

Topical steroids

Topical NSAIDs

Topical anti-histamines

Mast cell stabilisers

Question 15

What are some situations for which you’d give a patient topical steroids?

Answer 15

After cataract surgery

Uveitis

After corneal graft to prevent rejection

Question 16

What type of vasculitis, associated with polymyalgia rheumatica, can cause sudden onset headache and eventually visual loss due to infarction?

How is it treated?

Answer 16

Giant cell / temporal arteritis

Immediate oral prednisolone (dose depends on whether or not there’s visual symptoms)

Question 17

What are the specific eye side effects of steroids?

Answer 17

Cataracts

Glaucoma

Infection risk

Question 18

What is glaucoma?

Which visual field goes first?

Answer 18

Progressive optic nerve damage (sometimes due to raised intraocular pressure)

Peripheral vision

(Visual acuity is retained i.e they can see down the chart but their peripheries are gone)

Question 19

What is the only known risk factor for glaucoma?

Answer 19

Raised intraocular pressure

doesn’t mean that everyone with glaucoma has raised intraocular pressure

Question 20

What is the principle of glaucoma treatment?

Answer 20

Lower intraocular pressure to reduce progression of symptoms

You can’t stop the progression but you can slow it down

Question 21

What types of drug are used to treat glaucoma?

Answer 21

Prostanoids (“open outflow system”)

Beta blockers (e.g timolol, side effects, block ciliary body to reduce aqueous production)

Carbonic anhydrase inhibitors (e.g dorzolamide, same mechanism as beta blockers, side effects)

Alpha agonists (open outflow system and block ciliary body, high rate of allergy)

Question 22

slide 42

fluorescein injected, shows new blood vessels at macula

growth from corroid

> WET ARMD

Question 23

What are always given alongside intravitreal injections?

Why?

Answer 23

Antibiotics

Iatrogenic endophthalmitis almost always causes blindness in that eye

Question 24

Apart from antimicrobials and anti-inflammatories, what other functions do eye drops have?

Answer 24

Diagnostic e.g fluorescein

Local anaesthetic

Dilation e.g tropicamide

Question 25

What drops are put in to see the back of the eye better during examination?

Answer 25

Mydriatic drugs

e.g tropicamide

Question 26

What are the side effects of tropicamide?

Answer 26

Visual blurring

Very rarely acute glaucoma

Question 27

How does tropicamide work?

Answer 27

Blocks parasympathetic supply (sphincter pupillae) to iris - DILATION

Stops lens from focusing - CANNOT ACCOMMODATE

Question 28

What is acute angle-closure glaucoma?

Answer 28

Sudden increase in IOP blocks drainage of aqueous fluid

Red eye, acute headache and vomiting

Very rare side effect of tropicamide

Question 29

What type of drug is pilocarpine?

What disease is it used to treat?

What side effect does it cause?

Answer 29

Parasympathomimetic

Glaucoma

Reduces IOP by constricting pupil, which causes NIGHT BLINDNESS

Question 30

Many topical drugs can cause ___ reactions.

Answer 30

allergic

Question 31

Why should you never give steroids in herpetic keratitis?

Answer 31

Corneal melt

Question 32

vigabatrin - visual field constriction

ethambutol for TB - optic neuropathy

steroids - cataracts, glaucoma

chloroquine causes bullseye maculopathy

amiodarone leaves deposits in the cornea but is not clinically significant