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define glaucoma
group of ocular disorders characterized by changes in optic disk (optic nerve) that lead to optic neuropathy associated with visual sensitivity and field loss
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Risk factors of glaucoma
- age >40
- family hx (20% chance of developing if an immediate relative has)
- african american/asian decent
- diabetes
- long-term steroid use
- previous eye injury
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2 main types of glaucoma
- open angle (60-70%)
- closed angle (rare)
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_____ produces aqueous humor through filtration and secretion
ciliary body
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production of aqueous humor is influenced by:
blood pressure and intra-ocular pressure
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what receptors/enzymes are involved in secretion of sodium and bicarbonate:
- carbonic anhydrase
- alpha and beta receptors
- Na/K ATPases
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aqueous humor is secreted at a rate of
2-3 microliters/min
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aqueous humor leaves the eye in 2 ways:
- through the trabecular meshwork into the schlemm's canal (80-85%) then to the blood stream
- uveoscleral outflow: absorption into the iris blood vessels
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what is normal IOP?
10-20 mmHg
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IOP is affected by:
- pulse
- blood pressure
- coughing
- neck compression
- posture
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normal IOP is maintained by:
balance between fluid production and outflow
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increased IOP in glaucoma is due to:
decreased aqueous humor outflow through the trabecular meshwork
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How does an increase in IOP lead to blindness?
increased pressure from aqueous humor puts pressure on the vitreous humor (behind the lens) which puts pressure on the optic nerve which may lead to blindness
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Characteristics of open-angle glaucoma:
- second leading cause of blindness
- chronic, slow progressing generally gound in pts >50
- usually bilateral but one eye may be more affected than the other
- angle between the cornea and iris remains open
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secondary causes of open-angle glaucoma
- systemic diseases, trauma, surgery, lens changes, inflammatory diseases,
- drugs: corticosteroids, anticholinergics, vasodilators
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symtoms of open-angle glaucoma
- loss of peripheral vision but may be diagnosed before this is seen
- sensitivity to glare
- trouble differentiating shades of light
- may have an increase in IOP but not necessaryily for diagnosis
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Diagnosis of open-angle glaucoma
- comprehensive eye exams
- patients <45: no risk factors (every 4 yrs) with risk factors (every 2 yrs)
- patients >45: no risk factors (every 2 yrs) with risk factors (every yr)
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Prognosis of open angle glaucoma
- further visual field loss reduced by lowering IOP to <10-12 mmHg
- progression to bilarteral blindness: 4-22% of patients
- 60-80% of patients can have their IOP controlled with drug therapy over a 5 yr period
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define ocular hypertension
- patients with possible glaucoma (IOP >22 mmHg)
- don't treat, just watch and wait
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beta blockers
aqueous humor production- decreased
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carbonic anhydrase inhibitors
aqueous humor production- decreased
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trabecular outflow- increased
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prostaglandins
- trabecular outflow- increased ??
- uveoscleral outflow- increased
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adrenergic agonists
- aqueous humor production- increased/decreased
- trabecular outflow- increased
- oveoscleral outflow- increased
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alpha-2-agonists
- aqueous humor production- decreased
- uveoscleral outflow- increased???
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argon laser trabeculoplasty
- used to shrink part of the meshwork
- minutes to perform under local anethesia
- improves drainage of aqueous fluid and reduces IOP
- Complications: cataracts, inflammation, hemorrhage, chronic, macular edema
- typically used when drug therapy fails, is not tolerated, or becomes too complicated
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trabeculectomy (glaucoma filtration surgery)
- creates new drainage pathway
- 5-FU and mitomycin used to here to improved success rates by reducing the inflammatory response
- drainage implants: small silicon tube inserted into the eye to help with drainage
- typically considered when drug therapy fails
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drug therapy- beta blockers
- agent of choice
- lower incidence of local adverse effects
- precautions: pulmonary disease, bradycardia, 2nd or 3rd degree heart block, CHF, diabetes, myasthenia gravis, pt receiving oral beta blocker therapy
- Side effects: stinging, dry eyes, corneal anesthesia, blepharitis, blurred vision, decreased heart rate, reduced blood pressure, block symptoms of hypoglycemia
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Non-specific beta blockers
- timolol
- levobunolol
- metipranolol
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B-1 specific beta blockers
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ISA activity of beta blockers
carteolol
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precautions with carbonic anhydrase inhibitors
- sulfa allergies
- sickle-cell anemia
- respiratory acidosis
- pulmonary disorders
- renal disease
- diabetes
- hepatic disease
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Carbonic anhydrase inhibitors topical agents local side effects
- transient burning and stinging
- ocular discomfort
- blurred vision
- tearing
- every 12 hours administration produces less IOP reduction than every 8 hour dosing
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carbonic anhydrase inhibitors systemic sides effects
- malaise
- fatigue
- systemic acidosis
- anorexia
- nausea
- weight loss
- depression
- altered taste
- decreased libido
- increased uric acid
- renal stones
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Carbonic anhydrase inhibitors agents to use
- acetazolamide
- methazolamide
- dorzolamide (trusopt)
- brinzolamide (azopt)
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cholinesterase inhibitors in drug therapy
last line drugs, due to ocular and systematic toxic effects
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side effects of cholinesterase inhibitors
- similar to miotics
- fibrinous iritis
- iris cysts
- conjunctival thickening
- occlusion of the nasolacrimal ducts
- cataracts
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precautions with cholinesterase inhibitors
- asthma
- retinal detachments
- narrow angle glaucoma
- bradycardia
- hypotension
- HF
- seizures
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Miotic drug of choice
- pilocarpine
- ***patients with dark pigmented eyes may require higher concentrations of pilocarpine***
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topical side effects of miotics
- decreases in night vision
- frontal headaches
- eyelid twitching
- irritation
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systemic side effects of miotics
- diaphoresis
- N/V
- diarrhea
- caramping
- urinary frequencing
- bronchospansm
- heart block
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Name 2 miotics used
- carbachol (Isopto carbachol)
- pilocarpine
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characteristics of prostaglandin analogs
- drugs are more effective given at night than during the day
- maybe useful as first-line therapy in patients who cannot tolerate or have C/I with beta-blockers
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side effects of prostaglandin analogs
- uveitis
- changes in iris pigmentation
- hypertrichosis
- increased pigmentation in eyelashes
- ***color changes may be permanent and may takes months or years to become noticeable***
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Name 4 prostaglandin analogs
- latanoprost (Xalatan)
- travoprost (Travatan)
- unoprostone (Rescula)
- brimaprost (Lumigan)
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precautions agains adrenergic agonists
- cardiovascular disease
- cerebrovascular diseases
- closed-angle glaucoma
- hyperthyroidism
- diabetes
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topical side effects of adrenergic agonists
- tearing
- burning
- ocular discomfort
- browache
- loss of eyelashes
- blurred vision
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systemic side effects of adrenergic agonists
- increased blood pressure
- tachycardia
- arrhythmias
- tremor
- pallor
- anxiety
- increased perspiration
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name 3 adrenergic agonists
- diplvefrin (Propine)
- epinephryl borate (Epinal)
- epinephrine (glaucon)
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precautions with alpha-2-agonists
- structurally similar to clonidine
- apraclonidine is less used due to tachyphylaxis and more severe allergy rates
- precautions: cardiovascular disease
- renal disease
- cerebrovascular disease
- diabetes
- patients taking MAOIs, TCAs, or antihypertensives
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topical side effects of alpha-2-agonists
- ***usually a sign of allergic reaction and need to discontinue agent***
- lid edema
- eye discomfort
- foreign-object sensation
- itching
- systemic side effects: dizziness, somnolence, dry mouth, reduction in blood pressure and pulse
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name 2 alpah-2-agonists
- apraclonidine (Iopidine)
- brimonidine (Alphagan)
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Describle closed-angle glaucoma
- medical emergency
- less than 5% of glaucomas
- due to mechanical blockage of the aqueous humor outflow (closure of the angle) blockage usually by the peripheral iris
- symptoms: pain, vomiting, blurred vision, halos around lights, reddening of the affected eye, swollen or cloudy corneas, IOP >40 mmHg
- GOAL= rapid reduction of IOP, avoid surgery
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drug treatment for closed angle glaucoma
- pilocarpine
- beta-blocker
- alpha-2-agonists
- prostaglandin analogs
- carbonic anhydrase inhibitors
- the opposite eye should be treated as well
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