Glaucoma Pharmacology Flashcards
What are strong risk factors for getting glaucoma?
- high IOP
- aging (>40 y)
- family history - first degree relative
- race (blacks 4x)
- optic disc appearance
- corneal thickness >0.5 mm
What are the possible risk factors for getting glaucoma?
- high myopia (near sightedness)
- diabetes
- hypertension
- eye injury/surgery
What are the other risk factors that are possible for getting glaucoma?
- history of steroid use
- sleep apnea
- gender = male
What is the basic pathophysiology of experiencing glaucoma?
- when the axons going to the eye die off
- the axon plasma flows within the structures get cut off- nothing going to the eye
- the vasculature within the eyes gets pinched off and stops the blood flow from being carried to the rain
- when pressure within the eye increases, then there is a cut off of messengers from going outside of the eye
What is the upper limit of normal for IOP?
- 21 mm Hg is the upper limit of normal
- some are safe at 22-30 mm Hg
- some may have damage at < 21 mm Hg
What ethnic groups have a high rate of closed angle glaucoma?
- inuit of the north and Chinese or east indian groups
What is normal IOP?
- 10-21 mm Hg
Pressure within the eye is due to a pressure balance of ________. What produces this?
aqueous humor (AH) - ciliary body
What helps with drainage of IOP from the eye?
- trabecular meshwork
- canal of schlemm (80%)
- uveoscleral outflow (20%)
Open angle glaucoma is primarily a defect in what?
- primary a defect in decreased drainage
- tx: drainage and/or humour production
Closed angle glaucoma is primarily a defect of what?
- ballooning of the iris, aqueous humour flow is:
- increased pressure
- in an emergency situation acute drug treatment followed by surgery
What are the 2 main approaches to treating glaucoma?
- decrease production of AH
(receptors on ciliary body, carbonic anhydrase) - increase drainage
(trabecular meshwork and canal of scheme, uveoscleral outflow and surgical intervention)
For drugs to penetrate the epithelial layer, the drug should be ____
hydrophobic
For drugs to penetrate the stroma, the drug should be _____
hydrophilic
For drugs to penetrate the epithelial layer or the endothelial layer, the drug should be _____
hydrophobic
What should patients be counselled to do to stop the drug from getting into the systemic circulation?
- should always counsel the patient on how to compress the teat ducts- then this way you will stop the drug from going systemic
What is an example of a parasympathetic drug (miotics)?
- pilocarpine (receptor agonists), carbachol (receptor agonists)
- the peripheral vision starts to decrease to start off
What are common symptoms when the IOP gets over 60 mm of Hg?
- N/V, cramping, the person can see halos, the iris becomes unresponsive and will not move
- these attacks can occur intermittently or can occur all the time
- over time the person will need to receive treatment for this in order to stop the progression - will make a surgical tunnel going out tot he sclera, creating a bleb that drains fluid all the time
- can also use lasers to punch holes in the eyes to drain fluid
What are the most common SE of pilocarpine?
- increased outflow of aqueous humour pilocarpine for OAG and CAG
- poor night vision, blurred vision and aching
- loss of accompodative spasm with pilocarpine
- brow ache (this clears after about 2 weeks)
- contraindicated with miosis (this is undesirable)
Avoid strong miotics in _______
retinal detachment
What are some of the main SE of miotics?
GI, salivation
Why is nasolacrimal occlusion so important in drugs that are miotics?
- they can cause heart block, cramping and salivation
- if you decrease the amount of blood you get into the systemic circulation then you decrease the SE profile
What is a common complication of closed angle glaucoma?
- floppy iris
What is the MOA of epinephrine?
- improves outflow (uveoscleral and TM)
- acts on the alpha and beta adrenoreceptors in the ciliary body
- increased outflow (yet mydriasis) but may actually increase the aqueous humour production
- avoid in CAG
What are the systemic problems associated with drugs used for glaucoma?
- avoid in hypertension and heart disease
- adrenochrome deposits
What is the use of aproclonidine?
- used post eye surgery
- peak IOP
- aqueous humor production
What is the use of brimonidine?
- most common of this class
- aqueous humor production and increases outflow (uveoscleral)
- lowers IOP with minimal systemic effects
What is the class of a drug like timolol?
- beta adrenoreceptor blocker
What is timolol useful in?
- useful in OAG and CAG
- decreases the production of aqueous humour
What are the contraindications of beta adrenoreceptor blockers?
- heart failure
- asthma
- COPD
- diabetes
- heart block
- sinus bradycardia
What are examples of carbonic anhydrase inhibitors?
- topical is most frequent
- acetazolamide is used both orally and by IV
- inhibits HCO3 from forming in the ciliary body- aqueous humour production
- oral not for chronic use- useful for emergencies
- SE: metabolic acidosis, K depletion, fatigue, depression, allergies
Prostaglandin analogues are a ____ class of drugs for glaucoma
- novel
What is the MOA of prostaglandin analogues?
- decrease the IOP by increasing the uveoscleral outflow in humans - 20% of AH drained from this route
- increase this outflow by both relaxing the ciliary muscle and directly altering the extracellular matrix to decrease outflow resistance
Pilocarpine causes ciliary muscle ______ leading to outflow
contraction
Atropine causes ciliary muscle ______ leading to outflow
relaxation
What are the topical SE of prostaglandin analogues?
- allergy and conjunctival redness
- may increase/change iris pigmentation (brown)
- may produce eyelid darkening
- can increase eyelash thickness, number, pigmentation, size
What are the systemic SE of prostaglandin analogues?
- skin reaction, chest pain, muscle and joint pain, GI disturbances
What is the main use of hyper osmotic solutions?
- emergency management of angle closure
- may be used to decrease pressure pre-operatively
- avoid in severe dehydration, pulmonary edema and CHF
What kind of drug is considered the gold standard for treating glaucoma?
- beta blockers
- switch out for something else only if beta blockers are contra-indicated or ineffective
Try monotherapy with glaucoma drugs with what drugs?
- prostaglandins, local CAI’s, alpha2 agonist, if ineffective
Therapy should be started with _______
one eye
How often should the IOP be monitored once a patient is stabilized?
- the IOP should be monitored every 2-4 months
- visual field and optic disc should be monitored once yearly
_____ agents are useful for eye examinations
Mydriatic
_______ agents are useful for accurate refractions and providing relief from ciliary spasm during inflammation
Cycloplegic
______ drugs produce both mydriasis and cycloplegia
Parasympathetic
these are contraindicated in glaucoma
What are 2 examples of drugs that are parasympathetic?
- atropine and tropicamide
_____ drugs are mydriatic with little/no cycloplegia
Sympathetic
use caution of these drugs in glaucoma, heart disease and hypertension
What is an example of a drug that is sympathetic?
- phenylephrine
What is the function of the lens in the eye?
- the lens in the eye can focus light onto the retina and adjusts to focus objects both up close or far away providing for clear vision
Describe a sub-capsular cataract
- occurs at the back of the lens
- people with diabetes or those taking high doses of steroid medications have a greater risk of developing a sub capsular cataract
Describe a nuclear cataract
- forms deep in the central zone (nucleus) of the lens
- associated with aging
Describe a cortical cataract
- characterized by white, wedge-like opacities that start in the periphery of the lens and work their way in to the centre in a spoke like fashion
What is the most common cause of cataracts?
- aging
What are other causes associated with cataracts?
- prolonged use of corticosteroids
- statins
- phenothiazines
- inflammation
- trauma
- radiation exposure
- systemic disease(diabetes, wilson’s disease)
What are the clinical symptoms of cataracts?
-reduced vision, glare while driving during the dat and at night with headlights, dulling colours, double images
What is the most common post op complication?
- uveitis
Describe uveitis
- some inflammation in the anterior chamber is to be expected post op, however persistent inflammation beyond 4 weeks and or unusual severity early post op is not typical
What are some of the most common causes of uveitis?
- infectious endophthalmitis
- phacoanaphylaxis
- abrupt taper to corticosteroids
- patient non-adherence to corticosteroid drops
- pre-existing uveitis
- use of prostaglandin hypotentsive drugs
Describe infectious endophthalmitis?
- presents: worsening redness, pain, photosensitivity, and decreasing vision
- treatment: intravitreal ABs
What are the signs of post op intraocular pressure spikes?
- redness, pain, photophobia, IOP >35 mmHg, N/V can occur
What is the drug of choice in post op intraocular pressure spikes?
- beta blockers drug of choice
- avoid prostaglandins
What is the treatment to be used for a posterior capsule opacification?
- YAG capsulotomy (creates a hold in posterior opaque membrane)
- patient adherence to eye drop instructions is crucial to having a successful outcome in cataract surgery
