Ocular Disease, Pathology and Pharmacology
Concepts
Understand the major categories: anterior segment (keratitis, uveitis, conjunctivitis, dry eye), posterior segment (AMD, diabetic retinopathy, retinal detachment, glaucoma), and adnexal disease (blepharitis, chalazion, tumours). Know the mechanisms of common drugs: beta-blockers (timolol), prostaglandin analogues (latanoprost), alpha-agonists (brimonidine), carbonic anhydrase inhibitors (dorzolamide), and steroids. Understand the difference between bacterial, viral, and allergic conjunctivitis and their pharmacological management.
Traps
Examiners test side effects: timolol can cause bronchospasm and bradycardia; latanoprost causes iris darkening and eyelash growth; steroids can raise IOP and cause cataract. Watch for the distinction between anterior uveitis (cells and flare, photophobia) and conjunctivitis (discharge, no pain). Also know that prostaglandin analogues are first-line for open-angle glaucoma but contraindicated in pregnancy.
Worked example
A patient on timolol presents with wheeze and a pulse of 52 bpm. The likely cause is beta-2 blockade causing bronchospasm and beta-1 blockade causing bradycardia. Management: stop timolol and switch to a prostaglandin analogue or alpha-agonist.