Eye Disorder-glucoma Flashcards
Aqueous humour
Secreted by cells of the epithelium then into POSTERIOR CHAMBER (behind iris)
Then drains from ANTERIOR chamber to blood stream
Intraocular pressure IOP
Determined by the vol of aqueous humour in ANTERIOR chamber of eye
Glaucoma (raised IOP)
^IOP caused by blockage of circulation / drainage of AH
Result: damage /impaired blood sup to optic nerve -> which is slowly destroyed (irreversible)
Types of glaucoma
Chronic (primary) open angle glaucoma
Acute angle closure glaucoma (need surgery)
Congenital glaucoma
Secondary glaucoma
Treat primary/open angle glucoma
Prostaglandin analogue (1st line)
Beta-blocking analogue (2nd line)
Alpha 2 agonist (3rd line)
Carbonic anhydrase inhibitor
Prostaglandins drugs
*ends with oprost
Latanoprost
Bimatoprost
Prostaglandin MOA
*glucoma asymptotic- adherence / compliance to drug is major problem
Reduce IOP by increasing uveoscleral outflow
Outflow ⬆️~ pressure ⬇️
Possibly due to
• activation of molecular transduction cascade
• ^ in biosynthesis of certain metallo-proteinases
• reduction of extracellular matrix within uveoscleral pathway
Prostaglandin AE
Applies to >1% pts
Irreversible increase in iris pigmentation
Darkening , lengthening , thickening of eyelashes
Eye irritation, blurred vision
Beta receptors
B1 - heart
B2 - smooth muscle of bronchioles, aterioles, visceral organs
B3 - adipose tissue
Adrenergic receptors
Alpha 1,2
Beta 1,2,3
Cholinergic receptors
Nicotinic
Muscarinic
B blocker (b receptor antagonist) MOA
Block B2 : reduce aqueous humour formation
⬇️production =⬇️ pressure
May also act on b2 on ciliary arteries and induce vasoC - further ⬇️ ptoduction
B blocker AE
Systemic related ..
But and prevent by use appropriately
• close eye and pressure on tear duct for 3min after instillation
• systemic absorption reduce by up to 70%
• drug stay in eye rather than system
B blocker drugs
*end with : olol
Timolol
Betaxolol
Timolo
Non selective blocker
B1-heart B2-bronchioles
Not used in pts with cardio /airway disease
Betaxolol
Selective B1 (cardio) yet still works in eye
Dose related - efficiency
Use with caution in pts with airway disease
But contraindicate in cadio
Alpha 2 adrenergic agonist MOA
⬆️uveoscleral outflow = ⬇️ IOP
⬇️production = ⬇️IOP
A2 agonist AE
Palpitation : irregular and rapid heart beat
Hypertension
Tremors
A2 agonist drugs
* end with onidine
Apraclonidine
Brimonidine
Carbonic anhydrase inhibitor
* end with - zolamide
Aceta-zolamide (old - oral)
Brin-zolamide (new - topical)
Dor-zolamide (new- topical)
Carbonic anhydrase CA
Family of enzymes
Extremely rapid enzyme activity
Reversible
CA inhibitor
Reduces HCO3- synthesis
⬇️AH production = ⬇️ IOP
CA inhibitor (acetazolamide) in kidney
Inhib CA in lumen and proximal tubule of kidney
Reduction in H+ions for NA+ _ H+ exchanges
•hinders Na+ reabsorption and diuresis occurs
•NaHCO3 excretion ^
May result in mild / moderate metabolic acidosis
Cholinergic receptors (mus) M3
M3 : glandular / smooth muscle
(Stimulatory)
• gland secretion or muscle contraction
Iris and ANS
Two set of muscles with diff activation
Sphincter pupillae
Dilator pupillae
Sphincter pupillae
Circular group muscle
⬇️pupil size on contraction
M3 receptor of ParaSymNS stimulated
In bright light ( protective ) regulate how much light entering eye
Dilator pupillae
Radial group ⬆️ size of pupil
A1 of adrenergic of sympNS stimulated
When in dark (allow to see)
Pilocarpine
Not in use
Act on parasymp (cholinergic) M3
• constrict pupil
Increase outflow through trabecular meshwork
Acute ( angle closure) glaucoma
need laser iriditomy : laser create a hole on rim of iris, allow aqueous humour to flow
Drugs
- topical pilocarprine plus topical b blocker
- iv acetazolamide
- diuretics
Drugs for eye examinstion
anticholinergic - able to dilate eyes, as block m3 receptor activity on the sphincter pupillae
Atropine (Too long action duration)
Tropicamide (6hrs)
Cyclopentolate (24hrs)
Drugs for eye examination
Sympathomimics- mimic a1 receptor mediated actions , dilate eyes
Phenylephrine
Naphazolin
Tetrahydrozoline
Topical sympathomimetics also cause :
Vasoconstriction and decrease congestion of conjunctival blood vessel
⬇️redness
OTC meds
Especially
Naphzaoline and tetrahydrozoline
Sympathmimetics AE
Usually non
But concerns with elderly and children; also cardio pts
Could cause tachycardia and elevated BP
Ocular congestion drugs
Same as sympathomimetics
Phenylephrine
Naphazoline
Tetrahydrozoline
Dry eye syndrome drugs
Artifical tears
- carmellose
- hypromellose