3: Pharmacology Flashcards
How are drugs administered in ophthalmology?
Topically
Hydrophilic drugs cannot pass through the ___.
Hydrophobic drugs cannot pass through the ___.
epithelium because they’re not lipid-soluble
stroma because they’re not water-soluble
The epithelium of the cornea is ___.
The stroma of the cornea is ___.
The endothelium of the cornea is ___.
(hydrophilic / hydrophobic)
hydrophobic
hydrophilic
hydrophobic
like a big water sandwich
Which drugs can pass through the epithelium?
Which drugs can pass through the stroma?
Hydrophobic i.e lipid-soluble
Hydrophilic i.e water-soluble
lipid : water : lipid
Which type of drug easily penetrates the hydrophobic epithelium of the cornea?
Hydrophobic
i.e lipid-soluble drugs
Which type of drug easily penetrates the hydrophilic stroma of the cornea?
Hydrophilic
i.e water-soluble
Which topical antibiotic has both hydrophobic and hydrophilic properties?
Chloramphenicol
so it can pass straight through epithelium AND stroma
How are steroids made more hydrophobic?
What layer does this let them pass through?
ALCOHOL or ACETATE
Epithelium
How are steroids made more hydrophilic?
Which layer does this let them pass through?
PHOSPHATE
Stroma
What is added to topical drugs to act as a preservative?
Benzalkonium
How are topical eye drugs absorbed into the systemic circulation?
Inferior lacrimal papillae > Punctua > etc
Apart from topically, how else are eye drugs administered?
Subconjunctival injection
Subtenons (a surface under the conjunctiva)
Intravitreal (into the posterior chamber through the side)
Intracameral (into the front of the eye)
How are eye infections treated?
Topical antibiotics
Topical antivirals
How is eye inflammation treated?
Topical steroids
Topical NSAIDs
Topical anti-histamines
Mast cell stabilisers
What are some situations for which you’d give a patient topical steroids?
After cataract surgery
Uveitis
After corneal graft to prevent rejection
What type of vasculitis, associated with polymyalgia rheumatica, can cause sudden onset headache and eventually visual loss due to infarction?
How is it treated?
Giant cell / temporal arteritis
Immediate oral prednisolone (dose depends on whether or not there’s visual symptoms)
What are the specific eye side effects of steroids?
Cataracts
Glaucoma
Infection risk
What is glaucoma?
Which visual field goes first?
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)
What is the only known risk factor for glaucoma?
Raised intraocular pressure
doesn’t mean that everyone with glaucoma has raised intraocular pressure
What is the principle of glaucoma treatment?
Lower intraocular pressure to reduce progression of symptoms
You can’t stop the progression but you can slow it down
What types of drug are used to treat glaucoma?
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)
slide 42
fluorescein injected, shows new blood vessels at macula
growth from corroid
> WET ARMD
What are always given alongside intravitreal injections?
Why?
Antibiotics
Iatrogenic endophthalmitis almost always causes blindness in that eye
Apart from antimicrobials and anti-inflammatories, what other functions do eye drops have?
Diagnostic e.g fluorescein
Local anaesthetic
Dilation e.g tropicamide
What drops are put in to see the back of the eye better during examination?
Mydriatic drugs
e.g tropicamide
What are the side effects of tropicamide?
Visual blurring
Very rarely acute glaucoma
How does tropicamide work?
Blocks parasympathetic supply (sphincter pupillae) to iris - DILATION
Stops lens from focusing - CANNOT ACCOMMODATE
What is acute angle-closure glaucoma?
Sudden increase in IOP blocks drainage of aqueous fluid
Red eye, acute headache and vomiting
Very rare side effect of tropicamide
What type of drug is pilocarpine?
What disease is it used to treat?
What side effect does it cause?
Parasympathomimetic
Glaucoma
Reduces IOP by constricting pupil, which causes NIGHT BLINDNESS
Many topical drugs can cause ___ reactions.
allergic
Why should you never give steroids in herpetic keratitis?
Corneal melt
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
