Flashcards in Glaucoma Deck (27)
What are some fo the risk factors for glaucoma?
High intraocular pressure (>21 mmHg)
Previous ocular disease
What are the two types of glaucoma?
Which type of glaucoma is primarily treated with drugs?
What causes glaucoma?
An imbalance between the production of aqueous humour and drainage of aqueous humour
Where is aqueous humour produced?
Normally in the eye, why is there continuous flow and drainage of aqueous?
Because the pressure inside the eye is greater than the pressure outside in the episcleral vein and Schlemm's canal
What are the two pathways in which aqueous humour is drained?
Trabecular meshwork - main
Why is there resistance to flow in the uveoscleral pathway?
Because cells are tightly packed within tissues and therefore it is harder for humour to drain through
What are the drug classes for treatment options for glaucoma?
Prostaglandin + prostamide analogues
Carbonic anhydrase inhibitors
Where are FP receptors located?
Few in the trabecular meshwork
Ciliary body and muscle
Where are a2 receptors found in the eye?
Ciliary, conjunctival and corneal epithelial cells
Which drug classes reduce IOP by increasing uveoscleral outflow?
Prostaglandin and prostamide analogues
How do prostamide and prostaglandin analogues work?
They reduce resistance to uveoscleral outflow by remodelling the extracellular matrix. They do this by increasing matrix metalloproteinases which degrade collagen and the extracellular matrix, reducing the resistance of the sclera and ciliary muscle
What is the mechanism of action of timolol?
Decreases ion concentration, decreases fluid along gradient and so decreases aqueous humour production
Name a CAI used in the treatment of glaucoma
Acetazolamide - systemic CAI
Brinzolamide and dorzolamide - topical CAI
Which two drug classes are similar in the moa in terms of decreasing ion concentration, decreasing fluid along the gradient and reducing aqueous humour production?
B-blockers and CAIs
Which drug is used post-operatively in laser eye surgery?
Why is the long-term use of a2 adrenoreceptor agonists not sufficient in the treatment of glaucoma?
Because they densensitise quickly
What are some advantages of treatment using a2 adrenoreceptors?
Little effect on CV system
Name a a2 adrenoreceptor agonist
Which class of drugs causes CV side effects, bronchial side effects and diabetic side effects?
How do CAIs work?
inhibiting carbonic anhydrase which is needed in the production of bicarbonate. Bicarbonate is needed for aqueous secretion so by blocking this, aqueous humour production is reduced and IOP is lowered
Which is the least effective drug in lowering IOP?
How does pilocarpine work?
It mimics the effects of acetylcholine in the parasympathetic system
It contracts ciliary muscle
It pulls scleral spur
Opens the trabecular meshwork and so increases trabecular outflow, reducing IOP
What are the benefits of fixed dose combinations?
Reduced cost for patient
Reduced cost of treatment
Reduced exposure to preservatives
Which drug is used in emergencies only, where IOP is highly elevated and why?
Acetazolamide - due to severe side effects