Eye Disorders (Exam 2) Flashcards
Leading cause of blindness in US?
Age-related eye diseases
Amblyopia
Lazy eye
Strabismus
Imbalance of positioning of eyes
Glaucoma
Group of diseases that damage optic nerve and can result in vision loss and blindness
Glaucoma Progression
Ganglion cell death –> retinal nerve fiber layer change –> Optic nerve head changes –> Visual field changes
Primary Open-Angle Glaucoma (POAG)
Most common
Bilateral not always symmetric
Adult onset
Open, normal-appearing anterior chamber angles
Absence of secondary causes
Where do most medications of the eye act on?
Ciliary body and muscles
Open-Angle Glaucoma (OAG)
Intraocular pressure builds due to damage/blockage of drainage system in eye (trabecular meshwork)
Normal anatomy of the eye
Fluid flows freely through anterior chamber and exits through trabecular meshwork
What does open-angle mean?
Angle where iris meets cornea is wide and open
Angle-Closure Glaucoma
Less common
Blocked drainage canals leads to increased IOP (intraocular pressure)
Closed/narrow angle between iris and cornea
Types of eye drops to lower eye pressure
PROSTAGLANDINS
Rho kinase inhibitor
Nitric oxides
Miotic-cholinergic agents
Alpha-adrenergic agonists
Beta blockers
Carbonic anhydrase inhibitors
At risk population for Glaucoma
Elderly, african-americans, elevated IOP, relatives with glaucoma
Hyperopia (farsightedness)
High myopia (shortsightedness)
Which type of glaucoma doesn’t cause symptoms?
Open-Angle Glaucoma
Signs of Open-Angle Glaucoma
Gradual loss of peripheral vision
Tunnel vision is advanced stages
Signs of Angle-Closure Glaucoma
Develops suddenly
Sensitivity to light, cloudy eyes, halos around lights
Childhood Glaucoma
Asymptomatic in early stages
Congenital glaucoma
Total optic nerve atrophy and blindness
Causes of Secondary Glaucoma
Ocular vascular occlusion
Trauma, Uveitis, steroids, diabetes
High IOP correlates poorly with…
Presence of optic nerve damage
IOP level is related to…
POAG prevalence
MYOC or TIGR gene (GLC1A)
Chromosome 1
GLC1B
Chromosome 2
GLC1C
Chromosome 3
GLC1D
Chromosome 8
GLC1E
Chromosome 10
GLC1F
Chromosome 7
Where is MYOC gene located?
Long (q) arm of chromosome 1 between positions 23 and 24
Screening for POAG
IOP measurements
Optic disc evaluation
Visual field testing
Glaucoma Suspects
Normal visual fields; open, normal angles
+
Elevated IOP and/or abnormal optic disc/nerve fiber layer
Gonioscopy
Examination to see whether the area where fluid drains out of your eye is open or closed
Pachymetry
Medical device used to measure the thickness of eye’s cornea
Where is aqueous continuously produced?
By ciliary body on diurnal curve
What is the turnover of aqueous?
Every 1.5 to 3 hours
Aqueous flows…
from posterior chamber through pupil into anterior chamber
Where does aqueous filter?
Trabecular meshwork (90%)
Ocular venous system (10%)
—Uveoscleral outflow
Pupil is controlled by…
Sympathetic dilates by contraction of dilator muscle
Parasympathetic constricts by contracting sphincter muscle
Ciliary body is controlled by…
Sympathetic for aqueous production
Parasympathetic causing ciliary body muscle movement
Treatment of Glaucoma
Decrease IOP by decreasing aqueous production or increasing outflow
Medications that decrease aqueous production
Beta Adrenergic Antagonists
Systemic & Topical CA inhibitors
Medications that increase outflow
Prostaglandin Analogs
Cholinergic Agonists
Miotics: Parasympathetic Agents
Medications that decrease aqueous production and increase outflow
Adrenergic Agonists
Osmotic Agents
most beta adrenergic antagonists are
nonselective
beta adrenergic antagonist mechanism of action
reduce the production of the aqueous humor
beta adrenergic antagonists dosing
very effective
once to twice daily
side effects of beta adrenergic antagonists
worsening of asthma/emphysema, bradycardia, depression, confusion, worsening of myasthenia graves, low blood pressure, fatigue
betaxolol
betoptic
more selective than the other BAA on the eye
carries less risk of cardiac/pulmonary side effects
Timolol
timoptic
non selective BAA - blocks both beta1 and beta 2 adrenergic receptors
timolol does not have significant
intrinsic sympathomimietic activity, local anesthetic or direct myocardial depressant activity
timolol, when applied topically in the eye
reduces IOP whether or not accompanied by glaucoma
B-adrenergic blocking agents reduce
cardiac output in BOTH healthy subjects and patients with heart diseases
Pharmacokinetics of Timolol
well absorbed, considerable 1st pass metabolism
primarily excreted in urine
half life in plasma - 4 hours
Prostaglandin analogs MOA
increase the outflow of fluid from the eye
Prostaglandin analogs dosing
once a day
side effects of prostaglandin analogs
change color of the iris
thicken/darken eyelashes
redness of the eyes
inflammation inside the eye
examples of prostaglandin analogs
latanoprost - Xalatan
Travoprost - Travatan
Bimatoprost - Lumigan
Alpha Adrenergic Agonists MOA
reduce the production of aqueous humor and increase the outflow from the eye
act like adrenaline
Most popular adrenergic agonist
Brimonidine - Alphagan
Brimonidine side effects
12% risk of significant local allergic reactions
alpha 2 agonists
epinephrine - epifrin
dipivefrin - propine
apraclonidine - lopidine
brimonidine - alphagan-P
brimonidine and beta blocker - Combigan
Cholinergic agonists MOA
increasing the outflow of fluid from the eye
may lead to side effects if used frequently
short acting cholinergic agonists
Pilocarpine
Carbachol
Long acting Cholinergic agonists
echothiophate iodide
side effects of cholinergic agonists
headache
eyeache
smaller pupils
blurred/dim vision
nearsightedness
Carbonic Anhydrase MOA
bidirectional conversion of CO2 and H2O into bicarbonate and protons
play major roles in respiration, digestion and whole body/cellular pH regulation
carbonic anyhdrase inhibitors MOA
reduce IOP by decreasing ciliary body aqueous humor secretion
block active secretion of sodium and bicarbonate ions from the ciliary body to the aqueous
eyedrops forms of CAIs
dorzolamide - Truspot
brinzolamide - Azopt
dosing of CAI eyedrops
2-3 times a day (8-12 h)
oral forms of CAIs
Acetazolamide - Diamox
Methazolamide - Neptazane
Dichlorophenamide - Daranide
reasons to use an oral CAI over a topical CAI
may be used to remove fluid from the body, including the eye
why are oral CAIs limited in use?
they reduce body potassium
cause kidney stones
numbness or tingling sensations in the arms and legs
fatigue
nausea
Possible side effects of carbonic anhydrase inhibitors
possible metallic taste
frequent urination
tingling in the fingers and toes
(CAIs) systemic adverse effects are unusual despite the
accumulation of drug in red blood cells
timolol 0.5%/ dorzolamide 2%
Cosopt
dosed - bid
produced equivalent IOP lowering to each product dosed separately
Nasolacrimal occlusion
improves the therapeutic index of anti glaucoma medications
what does a nasolacrimal occlusion prevent?
prevents the drug from flowing into the drainage duct
more medicine in the eye –> drug is more effective
Dorzolamide MOA
Inhibition in ciliary processes
slows formation of bicarbonate ions –> reduction in fluid and sodium transport –> lower IOP
Dorzolamide accumulates in
RBCs during chronic dosing as a result of binding to CAII
N-desethyl metabolite
inhibits CAII less potently than dorzolamide
also inhibits CAI
this metabolite also accumulates in RBCs when its binds to CAI
after dorzolamide is stopped, the slower elimination phase has a half life of
four months
parasympathomimitic agents MOA
increasing the aqueous outflow from the eye
parasympathomimetic agents
mitotics
narrow the pupils
opposes adrenaline like substances
side effects of parasympathomimetic agents
a small pupil, blurred vision, aching brow, increased risk of retinal detachment
why are prostaglandins agonists/ Beta blockers used over parasympathomimetic agents used?
because parasympathomimetic agents are used 3-4 times a day and the others are less
pilocarpine
used to keep pupil small in patients with plateau iris
used in patients with a narrow angle prior to laser iridotomy
osmotic agents
treat sudden forms of glaucoma where the eye pressure remains extremely high despite other treatments
osmotic agents examples
isosorbide
mannitol
isosorbide
Ismotic
by mouth
release pressure via vasodilation
mannitol
osmitrol
IV
release water content via diuresis
MOA of mannitol
in the intravascular space increases the tonicity of the blood plasma
draws water out into intravascular space
once here, the mannitol is excreted in kidneys
MOA of isosorbide
vasodilators
relaxing the blood vessel, heart doesn’t work as hard, doesn’t need as much oxygen