Eye Drugs

Question 1

Causes of Mydriasis

Answer 1

Low light
Muscarinic Antagonists
Sympathetic Stimulation (weak)
Alpha 1 agonists (weak)

Question 2

Causes of Miosis

Answer 2

High light
Parasympathetic stimulation (weak)
Muscarinic Agonists
Alpha 1 antagonists (weak)

Question 3

Drug Absorption

Answer 3

Generally topical- minimise adverse systemic effects
Slow release formulations: reduce risk of SEs
Uncharged and lipophilic to cross cornea
Nasolachrymal Drainage: Key in systemic absorption
Circumvents hepatic first-pass metabolism

Question 4

Eye Colour

Answer 4

Increased Melanin causes drugs to bind

Slower onset and longer duration

Question 5

Ophthalmic Diagnosis

Answer 5

Mydriatics used to look at fundus
Muscarinic antagonists: Topicramide, 1-3 hours duration, little cycloplegia
Adrenaline is less effective but no cycloplegia via alpha1

Question 6

Glaucoma

Answer 6

Poor drainage of aqueous humour (Canal of Schlemm)
Increased intraocular pressure- >21mmHg
Changes to fundus (optic disc cupping)
Can cause permanent damage to optic nerve
Open angle and closed angle

Question 7

Open-Angle Glaucoma- Dec. Production

Answer 7

Beta-Blockers- Timolol- decreases blood flow in ciliary body
Caution- OLD, Asthma, Bradycardia, HF due to systemic absorption
Carbonic Anhydrase Inhibitor- Dorzolamide- Dec. HCO3- leading to dec Na+ and aqueous formation

Question 8

Open-Angle Glaucoma- Inc. Drainage

Answer 8

Miotics-Pilocarpine- Increases uveoscleral outflow
SE: Long-term pupil constriction, accomodatin spasm- blurred vision, headaches
Prostaglandin- Lanaprost- PGF2alpha analogue, increase drainage

Question 9

Alpha-2 Agonists

Answer 9

Brimonidine- Chronic open-angle when other agents ineffective
Used alone or with Beta-Blocker
MOA: Decrease aqueous humour production- vasoconstriction
Increased uveoscleral outflow- prostaglandin release

Question 10

Closed-Angle Glaucoma

Answer 10

Cut hole in Iris

Mydriatics may make it worse by reducing drainage

Question 11

Age-Related Macular Degeneration

Answer 11

Affects elderly: Most common blindness in UK
Cause unknown: Central retinal pathways deteriorate- dry
10% have neovascular “wet” AMD. New blood vessels leak under retina and can be rapid onset

Question 12

Wet AMD Therapy

Answer 12

Photodynamic therapy- Verteporfin taken up by endothelium, apply laser, free radicals destroy new vessels
VEGF MAb- Ranizumab- binds and inhibits VEGF in retina, slowing progression