Clinical CNS Eye Flashcards
Is glaucoma just elevated IOP?
No, not always
What is glaucoma?
An irreversible, progressive disease of the optic nerve associated with characteristic optic nerve head changes and visual field defects, which untreated results in tunnel vision and eventually blindness
What is the lamina cribosa?
1-2mm in diameter
Supporting structure, holes in this structure allows axons of retinal ganglion cells to exit the eye
Describe the optic nerve head:
Where the optic nerve exits the eye via the lamina cribs
There are no photoreceptors here
AKA optic disc is the cause for the normal ‘blind spot’
Where BVs enter and exit the eye
What occurs if there is damage to the optic nerve head?
May relay to an area of retinal ganglion cells, create a visual field defect:
-superior compared to inferior damage
-damage to superior fibre leads to large area of damage so defect on inferior
-progression of disease, an arcuate area e.g inferior which is associated with arcuate superior
Can then join up to form a common arc
What is visual field analysis?
Computerised automated visual field analysis which is printed out
What does the optic disc look like normally compared to a person who has glaucoma?
Normal- small pale depression in the middle
Glaucoma- enlarged hole and brighter; the nerve tissue has become damaged and disappeared, increased cup, decreasing rim
Name the different types of glaucoma:
Congenital vs acquired*
1º* vs 2º(due to another ocular condition)
Open angled vs closed angle
What is closed angle glaucoma?
Drainage angle between cornea and iris
Usually due to pupil block
Edge of iris rests on lens, causes relative block of flow of aqueous from posterior to anterior chamber so increases pressure in posterior, pushes iris forward so no fluid to exit and increase pressure
What are the normal values for IOP?
Mean= 16mmHg
SD= 2.5
Range= 11-21
Non gaussian, skewed to high so normal around 11-24
What is primary angle closure (PAC)?
Irido-corneal angle occlusion
What are the different classifications of PAC?
PACS (suspect)
PAC (established)
PACG (glaucoma)
Both acute (medical emergency) and chronic
Who does PAC normally affect?
Small hypermetropic (long sighted) eyes
What are the types of treatment for PAC?
Laser iridotomy or cataract surgery (small hole in iris so aq released)
Medicine
Glaucoma surgery
What are the symptoms of acute angle closure (AAC)?
Painful red eye
Blurred vision/ haloes
N&V
Mid-dilated pupil
Cloudy cornea
Shallow anterior chamber
Elevated IOP
Closed angle at gonioscopy
Glaukomflecken (small white pasties on front of lens)
Other eye PAC(s)
Cataracts
Name topical mydriatic (dilatory) drugs which can cause drug induced angle closure (DAC):
Topicamide
Cylopentolate
Phenylephrine
Atropine
Name nebulised drugs which can cause drug induced angle closure:
Ipatropium
Salbutamol
Ephedrine
Name oral/ IV drugs which can cause drug induced angle closure:
TCA (amitriptyline etc), SSRIs (paroxetine, citalopram)
Epinephrine
Anticholinergics (e.g oxybutinin)
Atropine
Name other drugs (very rare) which can cause drug induced angle closure:
Topiramate
Hydrchlorthiazide
Acetazolamide
Quinine
Tetracycline
Pilocarpine
Botox
OTC flu remedies
What is POAG?
Primary open angle glaucoma- most common type of glaucoma in UK
-initially asymptomatic
-usually slowly progressive
-often presents late
Describe the epidemiology of POAG:
67 mill cases worldwide (10% blind)
In caucasian population:
-1% at 50yrs
-4% at 80yrs
-15% at over 80 yrs
For each 1-2 diagnosed another is undiagnosed
What is the aetiology of POAG?
Poorly understood
Most freq associated with raised IOP
Multifactorial pathogenesis:
-mechanical- movement of laminal cribosa- direct trauma to retinal ganglion
-ischaemic- problems at optic nerve head