glaucoma 1 Flashcards
what is glaucoma?
Glaucoma is a group of eye diseases that can lead to blindness if untreated
what is the Palpebral fissure?
the space between the two eyelids. the narrow side is called the lateral angle and the side closer to the nose is called the medial angle.
describe the flow of tears?
tears are produced in the lacrimal gland.
it is then transported from Lacrimal ducts>Superior or inferior lacrimal> canal Lacrimal ducts>Nasolacrimal duct>Lacrimal sac>Nasal cavity
what is another name for the upper and lower eyelid?
palpebra
how many layers are there in the eye?
3 layers- sclera, choroid and retina
what do the Zonula fibers do?
they are suspensory ligaments attached to the lens. if they move so do the lens.
what is another name for the optic disk?
blind spot
what part of the retina does the visual axis lye on?
Fovea centralis
how is the aqueous humour formed?
Aqueous humouris formed by capillary network in ciliary body
where us the aqueous humor drained?
Drains into the canal of Schlemm,>Eventually enters the blood
what is the drainage of aqueous humor balanced by?
balanced by the rate of secretion. and because of this the IOP is maintained at 10-20mmHg
when is the IOP at max and min?
IOP maximum - 8.00 -11.00am; minimum -midnight -2.00pm
what is the The production of aqueous humour is indirectly related to ?
blood pressure and blood flow in the ciliary body
how much aqueous humour is formed every minute?
3 microlitres per minute
what is the fate after it enters the anterior chamber?
10%- Uveoscleral outflow tract
90%- Episcleral veins(venous plexus)
what is the adrenergic receptor response in the: Iris radial muscle, ciliary epithelium ,Ciliary muscle and Lacrimal gland?
iris radical muscle- A2-Mydriasis-dilation of pupil
ciliary epithelium- A2/B2-Aqueous humour production
Ciliary muscle-b2- relaxation
lacrimal gland-A2- secretion
what is the Cholinergic receptor subtype and response in :Iris sphincter muscle, ciliary muscle and lacrimal gland?
m3- miosis
m3- accommodation
m2/3- secretion
how many types of glaucoma are there? and what are they?
5 1-Chronic open – angle glaucoma (COAG) 2-Normal tension glaucoma 3-Ocular hypertension (OHT) 4-Primary angle –closure glaucoma (PACG) 5-Secondary glaucomas
what is COAG?
Relative obstruction of aqueous outflow through the trabecular meshwork, usually affects both eyes
what is normal tension glaucoma?
IOP not raised on initial screening although signs of damage are present
what is OHT?
Elevated IOP in absence of visual field loss orglaucomatous optic nerve damage
What is PACG?
Closure of the angle by peripheral iris results in reduction of aqueous outflow.
mostly in women
what is secondary glycomas?
Arise for a number of reasons (inflammation, intraocular tumour, raised episcleral pressure or congenitally due to developmental abnormalities)
how is glaucoma caused?
caused by poor drainage of aqueous humour and can cause blindness
how is glaucoma characterised?
Increase in IOP to more than 21mmHg
•Changes in the fundus , in particular optic disk ‘cupping’
•Visual field changes
•If untreated , glaucoma permanently damages the optic nerve and this can cause blindness
what are Ocular Prostanoids?
ester compounds that cause a fall in IOP by increasing the uveosleral outflow with no significant effect on other parameters of aqueous humour
what does Lasanoprost do?
it is an ocular prostanoid that :converted to its active free acid on entering the eye
administered in the evening
what does Travosprost do?
Ester prodrug converted to its active form by cornealhydrolytic enzymes as it is absorbed from the eye
•Potent full agonist of PGF2α- receptor
what does Bimatoprost do?
Fatty acid amide similar to PGF2α1-ethanolamide
•Lowers IOP to a greater extent than any topicalocular hypotensive which is sustained for at least 4years
what do b-blocker adrenoreceptor agonists do?
Blocked of ciliary β-receptors , preventing the cyclic AMP –induced rise is aqueous secretion.
•Reduce aqueous humour formation rather than increase outflow
what is seen in Beta –adrenoceptor antagonists?
bradycardia
Episodes of orthostatic hypotension & syncope in elderly
bronchospasm
what are the two sympathetic agents used?
Apraclonidine
Brimonidine
how does Apraclonidine work?
•α2-selective agonist ; in high conc. activates α1-receptors
- Activation ofα2–dec ciliary body aqueous humor
- Activation of α1- dec ciliary blood flow
- Activation of postsynaptic α2- autoreceptors-dec NA release aqueous humour following diminished postsynaptic βreceptor stimulation
how does brimonidine work?
- More α2- selective
- Results in miosis rather than mydriasis
- Used alone or adjunct to β–blockers & PGA
- dec aqueous humour production & increase uveoscleral flow
when is Brimonidine used in caution?
Used with caution severe coronary artery disease
and Contraindicated in patients taking MAOIs , TCA
what is Pilocarpine?
it is a miotic
Stimulation of ciliary muscle- increases outflow of aqueous humour & opening of channels of trabecular meshwork
why is Pilocarpine not patient compliant
Onset of action 19 mins.; Short duration of action ; 4times daily- therefore, mainly used in secondary glaucoma
how many forms of Carbonic anhydrase inhibitors are present in the eye? and what are they?
3 forms
CA1,CAII AND CAIV
how do Carbonic anhydrase inhibitors work in the eye?
inHibit CAII
Formation of bicarbonate ions and their secretion Into the posterior chamber
2. DECREASED sodium transport into posterior chamber
3. Lowering IOP
Are carbonic anhydrase inhibitors used in combination?
yes- for a more desired effect
what hyperosmotic agents are used and why?
glycerol orally and mannitol IV due to their speed of action and effectivenss in an emergency
after administration of a hyperosmotic agent what happens?
inc in plasma osmolarity
net water movement
reduced IOP
why is PACG a medical emergency?
Without treatment blindness may occur in 1-2 days
•Usually a permanent cure is produced by lasersurgery
