Glaucoma Flashcards
What is the average intraocular pressure (IOP)?
15.5
Can reach a maximum of 21 before damage becomes a risk
Damage can still occur from pressures in the normal range
How common is progressive open angle glaucomas?
commonest cause of treatable blindness after cataracts in the developed world
1% of >40yrs and 5% of >75yrs are affected
What are the risk factors for glaucomas?
Raised IOP Family history- most important Myopia Black race Diabetes
What is the pathology for glaucomas?
raised IOP +/- vascular factors lead to a loss of retinal nerve fibres and optic disc excavation (cupping)
this leads to visual field defects, tunnel vision and blindness
Asymptomatic disease and doesn’t present until the patient is almost blind
Usually asymmetrical with one eye leadign the way
What should regular assessment to detect glaucomas include?
IOP readings, visual fields analysis and optic disc examination (fundoscopy)
Signs include a high level of cupping and optic disc atrophy (blurring of borders)
the cup to disc ratio should be largest inferiorly then superiorly, nasal, temporal (ISNT)
What is an acute angle closure glaucoma?
Acute high pressure eye with pain, blurred vision and vomiting
Corneal oedema
Red eye
A fixed mid-dilated pupil
Risk factors: hypermetropia and a family history
What is the pathology of acute angle closure glaucoma?
The lens gradually grows bigger with age and pushes the iris closer to trabecular meshwork
Eventually iris will completely block off the trabecular meshwork so drainage will cease but production of aqueous will continue
Going to bed may help as the pupil constricts and the iris pulls away from the trabecular meshwork- hence patients may have symptoms for several weeks before the full blown attack
What is the treatment for acute angle closure glaucoma?
Pilocarpine & acetazolamide
laser iridotomy trabeculectomy
What is a rubeotic glaucoma?
follows central retinal vein occlusion or diabetic retinopathy
New vessels form and occlude the angle
This is rarer now
What are the symptoms of a rubeotic glaucoma?
Pain and reduced vision Red eye Corneal oedema Rubeosis Pupil distortion
What are the early field loss values associated with IOP?
IOP >30- blind in 3 years
IOP 25-30- blind in 6 years
IOP 21-25- blind in 15 years
What is the Goldmann method?
Visual field testing
hollow white spherical bowl positioned a set distance in front of the patient, examiner presents a test light of variable size and intensity
the light may move towards the centre from the perimeter (kinetic perimetry), or it may remain in one location (static perimetry)
test the entire range of peripheral vision, and has been used for years to follow vision changes in glaucoma patients
What is automated perimetry?
uses a mobile stimulus moved by a perimetry machine
commonly used for early detection of blind spots
Patient sits in front of an (artificial) small concave dome in a small machine with a target in the centre- the chin rests on the machine and the eye that is not being tested is covered
a computer then shines lights on the inside of the dome and the patient clicks the button whenever a light is seen
The computer then automatically maps and calculates the patient’s visual field
What are the eye drops used to lower IOP?
Prostaglandin analogues (latanoprost)
Beta blockers (timolol)- slows down aqueous production
Carbonic anhydrase inhibitor (dorzolamide)- slows down aqueous production
Alpha agonist (brimonidine)- slows down production and increases outflow
Cholinergic (pilocarpine)-increases outflow
(tablets, carbonic anydrase inhibitors can be used
What laser can be used for treatment of glaucomas?
Argon/selective laser trabeculoplasty, where 50-100 shots are delivered around the trabecular meshwork to try to increase drainage Can be used in most age groups and even as a primary treatment, requires an open angle
What surgery is available for treatment of glaucomas?
trabeculectomy- creates a controlled fistula where aqueous leaks out under the conjunctiva, leaves a bleb in the eye, the success rate is 50-90% with an IOP Risk factors for failure: Previous surgery Black race Long term topical medications: esp pilocarpine Co-existing uveitis- past or present Diabetes- esp with retinopathy
What are the side effects fo medications used for glaucomas?
Beta blockers- cardiac and respiratory effects
Alpha agonists- dizziness, syncope and allergy
Prostaglandin analogues- lash growth, pigmentation (permanent iris colour change)
Cholinergic- eye ache, dim vision
Carbonic anhydrase inhibitors- taste problems, acidosis
What are the advances for topical medication for glaucomas?
Combination agents:
Prostagladin analogue & beta blockers
Alpha agonist & beta blockers
Carbonic anhydrase inhibitors & beta blockers
Preservative free drops (some people allergic, more expensive)
Beta blockers
Carbonic anhydrase inhibitors
Cholinergic
Alpha agonist
What have been the advances in glaucoma surgery?
Anti-metabolites- 5FU and mitomicin (chemotherapy)
Laser suture lysis/releasable
Microtrabeculectomy
Phacotrabeculectomy- deep sclerectomy/viscocanalostomy
What are the risk factors for acute angle closure glaucoma?
hypermetropia (long-sightedness)
a shallow anterior chamber
female gender
What are the functions of the eyedrops used to treat AACG?
a direct parasympathomimetic (e.g. pilocarpine, causes contraction of the ciliary muscle → opening the trabecular meshwork → increased outflow of the aqueous humour)
a beta-blocker (e.g. timolol, decreases aqueous humour production)
an alpha-2 agonist (e.g. apraclonidine, dual mechanism, decreasing aqueous humour production and increasing uveoscleral outflow)
intravenous acetazolamide
reduces aqueous secretions
