Week 2- Conditions Affecting the Aqueous, Vitreous, Flashcards
What are the functions of aqueous humour?
*Maintains intraocular pressure
*Supplies nutrients and removes waste from the avascular tissues of the eye, including
the cornea, lens & vitreous.
*Plays a critical role in the optical clarity of the eye
What is glaucoma?
*An initial event or series of events.
*Obstruction of aqueous humor outflow.
*Increased IOP too high for optic axoplasmic flow.
*Increased vitreous glutamate
*Retinal ganglion cell dysfunction with resulting optic nerve degeneration and atrophy.
*Visual field loss and blindness.
What is Primary Angle Closure Glaucoma?
iris blocks fluid from draining out of the eye, causing pressure to build up
What are the effects of elevated intraocular pressure?
*Pressure on retina & optic nerve head
*Optic nerve axons, retinal ganglion cells:
Impact on perfusion
Impact on axoplasmic flow
(Vitreal glutamate)
What are the signs of acute glaucoma?
Pain
* Episcleral congestion (also, potentially, conjunctival
congestion)
* Corneal oedema
* Corneal vascularisation (deep ‘brush-border’
appearance; can advance up to 1mm/day)
* Mydriasis (mid-dilated, unresponsive pupil; important
to check consensual PLR in other eye)
* Optic nerve head swelling and/ or haemorrhage may
be present
* Usually normal ERG
* May have vision loss
What are the signs of chronic glaucoma?
*Pain less evident
*Haab’s striae
*Corneal oedema
*Buphthalmos
*Iris atrophy
*Ciliary body atrophy
*Lens luxation /subluxation
*Optic nerve atrophy
*Retinal atrophy
*ERG absent
What are the diagnostic techniques used for?
*Thorough ocular examination
*Tonometry
(Digital)
Indentation
Applanation
Rebound
*Fundoscopy
*Gonioscopy
*ERG
What is Xalatan?
a prostaglandin analogue; a powerful antiglaucoma medication; can use as first
line treatment (1 drop 3x within the first hour) in acute glaucoma whilst awaiting urgent referral
appointment to a veterinary ophthalmologist. (Avoid using in cases with concurrent lens luxation or
uveitis)
What is Brinzolamide (Azopt) or Dorzolomide (Trusopt) ?
carbonic anhydrase inhibitors; can be given even in the
case of concurrent lens luxation
What is Timolol 0.5% drops?
beta-adrenergic blocker. Side effects include miosis, conjunctival hyperaemia, local
irritation, bradycardia, hypotension. (Avoid in cases of uveitis, anterior lens luxation and heart
failure)
What are Osmotic diuretics?
rarely used due to risks, contraindications and practical difficulties
What is Hyalitis?
inflammatory exudate (which can be yellow in colour)
Uveitis, optic neuritis, panophthalmitis and retinochoroiditis
What is Synchisis scintillans?
Pathological process – liquified vitreous
Golden brown, refractile bodies
Settle if head is shaken
What is Asteroid hyalosis?
Degenerative disorder - older animals
Whitish refractile bodies
Do not settle if head is shaken
Lipid / calcium phosphate mineral complexes
What is inherited retinal degeneration?
- Tapetal hyperreflectivity
- Pigmentary changes
- Blood vessel attenuation
- Optic nerve atrophy
How would you diagnose retinal detachment?
- Ophthalmoscopy
- Sometimes it is visible in the pupil without
ophthalmoscopy - Ultrasound
How would you treat retinal detachment?
- Cage rest
- Diode laser
- Appropriate treatment, e.g. amlodipine, and/ or
specific treatment for underlying cause of
hypertension, if due to hypertensive retinopathy (see
later) - Presumed neuroprotective medication (used
empirically?)
What is hypertensive retinopathy?
Often presented for acute blindness
* Dilated, poorly to unresponsive pupils
* Retinal detachment with retinal and vitreal haemorrhages
* Can be primary or secondary:
* Primary <5% of all cases
* Secondary: Causes may include renal failure,
hyperthyroidism, high-salt diet, atherosclerosis etc
