24 - Glaucoma Flashcards
What are the main risk factors for glaucoma?
- High intraocular pressure (greater than 30 mmHg)
- Aging
- Family history (primary relative)
- Race (black and Hispanic)
- Optic disc appearance
- Corneal thickness greater than 0.5 mm
What is used to diagnose glaucoma?
Optic disc appearance
What is the normal intraocular pressure? What is considered high intraocular pressure?
- Normal = 10-21 mmHg
- Pressure over 21 mmHg doesn’t mean it is a problem, so no real definition of high IOP
- General rule = if glaucomatous damage, lower the IOP
Intraocular pressure is due to _____
Balance of aqueous humor
Where is aqueous humor produced? Where is it drained?
- Produced continuously in ciliary body
- Drained into trabecular meshwork (80% into canal of Schlemm and 20% into uveoscleral outflow)
What is the primary defect in open angle glaucoma? What is the tx?
- Primary defect = decreased drainage
- Tx = drainage and/or humor production
What is closed angle glaucoma?
- Ballooning of iris causing decreased aqueous humor flow, increasing pressure
- Emergency situation
- Acute drug tx followed by surgery
What are the sx of open angle glaucoma?
- Most people are asymptomatic
- By the time they see sx, 25-30% of axons of optic nerve are gone
- Gradually lose ability to see colour and contrast
What are the 2 tx approaches for glaucoma? How is each carried out?
1) Decrease production of aqueous humour – target receptors on ciliary body (alpha or beta) or carbonic anhydrase
2) Increase drainage – target trabecular meshwork and canal of schlemm, uveoscleral outflow, or surgery (if drugs don’t produce desired outcome)
Which drugs are parasympathomimetics? What is their effect? What is their dosage? What are some SE? When are they contraindicated?
- Pilocarpine, carbachol
- Increase outflow of aqueous humour
- Dose = drops 2-4 times/day; gel for 1 day; inserts for 7 days
- SE = poor night vision, blurred vision, aching, brow ache (clears after 2-3 weeks), GI, salivation
- CI when miosis undesirable (ex: iritis), retinal detachment
What are the categories of drugs used for glaucoma?
1) Parasympathomimetics (miotics)
2) Sympathomimetics
3) Beta blockers
4) Carbonic anhydrase inhibitors
5) Prostaglandin analogues
6) Hyperosmotic solutions
What is the effect of sympathomimetics? When are they contraindicated?
- Improve outflow (uveoscleral and trabecular meshwork)
- Acts on alpha and beta adrenoreceptors in ciliary body; increase outflow but may increase aqueous humor production
- CI in closed angle glaucoma, hypertension and heart disease
Which sympathomimetics are used for glaucoma and when?
- Aproclonidine used post eye surgery
- Brimonidine is most common; lowers IOP w/ minimal systemic effects
What is the first line for glaucoma?
- Beta blockers
- Specifically timolol, levobunolol, and betaxolol
- Used in open and closed angle
What is the effect of beta blockers in the eye? When are they contraindicated?
- Decreased aqueous humour production
- CI = heart failure, asthma, COPD, diabetes, heart block, sinus bradycardia
What is the effect of carbonic anhydrase inhibitors in the eye? Which formulation is most commonly used? What are some SE?
- Inhibit bicarbonate formation in ciliary body, so decrease aqueous humour production
- Topical is most common (brinzolamide and dorzolamide)
- SE = metabolic acidosis, K+ depletion, fatigue, depression, allergies
What is the effect of prostaglandin analogues in the eye?
- Decrease IOP by increasing uveoscleral outflow
- Increase outflow by both relaxing ciliary muscle and directly altering extracellular matrix to decrease outflow resistance
Which prostaglandin analogues are used for glaucoma? What are some SE?
- Latanaprost, travoprost, bimatoprost, and tafluprost
- Topical SE = allergy and conjunctival redness, change iris pigmentation, produce eyelid darkening, increase number, thickness, and pigmentation of eyelashes
- Systemic SE = skin reaction, chest pain, muscle and joint pain
When are hyperosmotic solutions used for glaucoma? When should they be avoided?
- Emergency
- May be used to decrease pressure pre-op
- Avoid in severe dehydration, pulmonary edema, and congestive heart failure
Which classes of drugs decrease aqueous humour production?
- Beta blockers
- Alpha 2 agonists (sympathomimetic)
- Carbonic anhydrase inhibitor
Which classes of drugs increase outflow?
- Parasympathomimetics
- Epinephrine and alpha 2 agonists (sympathomimetics)
- Prostaglandin analogue
What is the tx plan for glaucoma?
- Go w/ beta blocker first
- If beta blocker CI or ineffective, try monotherapy w/ prostaglandin, local CA inhibitor, or alpha 2 agonist
- If these ineffective, try combinations of beta blocker + (PG or topical CA inhibtor or miotic) or PG + (CA inhibitor or alpha 2 agonist)
- Parasympathomimetics are 3rd line b/c of side effects; may be used as miotic w/ PG or beta blocker
What is tx goal for primary open angle glaucoma?
Lower IOP by 20-30% from baseline
Should glaucoma therapy be started in one or both eyes? What should be done if tx is not tolerated?
- Start in one eye, if tolerated treat both
- If not tolerated, switch to alternative agent (sometimes same class but different formulation)
