Ophthalmology uveitis and glaucoma Flashcards
What are the two parts of the ciliary body
Pars plicata which produces aqueous and is the origin of the zonules
Pars plana which merges with the retina
What is the choroid
A layer of pigmented, vascular and lymphoid tissue behind the retina
Where is the reflective tapetum found
Within the inner choroid
Function of the choroicapillaris
To supply nutrients to the inner retina via retinal pigment epithelium
What is anridia and which domestic species does it affect
Lack of iris
Due to mutation in pax-6 homeobox genes; out of domestic species just horses seem to be affected
What does correctopia mean
Abnormal pupil position
Where is an iris coloboma usually seen
Ventrally
What does dyscoria mean
Abnormal pupil shap
What is the most common congenital defect of the uveal tract
Persistent puppilary membranes = vascular remnants from development; can cause cataract
What sections of uveal tract could uveitis affect
Anterior = iris
Intermediate = ciliary
Posterior = choroid
If all inflamed = panuveitis
What is rubeosis iridis
Red tinge to iris due to formation of new blood vessels in uveitis
WHy might we get a reduction in intraocular pressure in uveitis
Due to loss of function of the ciliary body
What is the classic triad of signs in uveitis
Miosis
Photophobia
Inflammatory cellular involvement
What are the main infectious causes of uveitis in the cat
TIP, FIV, FeLV, Toxoplasma
What infection in the cat causes pyogranulomatous inflammation and vasculitis with prominent rubeosis iridis
Feline infectious peritonitis (FIP)
How do common causes of uveitis differ in the dog and cat
In the dog it is mostly idiopathic and non-infectious; commonly see trauma and lens induced uveitis
In cats usually infectious
What causes lens induced uveitis
Gradual leakage of lens proteins (soluble) through lens capsule; triggers immune response since these antigens are ‘foreign’
Seen in diabetes as lens expands but capsule doesn’t
Get very dark brown iris
What type of uveitis is associated with dark brown iris
Lens induced
What is reflex uveitis
Specific traumatic uveitis condition; corneal injury leads to trigeminal nerve response to cause miosis; whole eye muscle ends up in spasm
Need atropine to stop this
What is Vogt-Koyanagi-Harada like syndrome
Autoimmune reaction against melanin-associated antigen in pigmented uvea and skin
–> Causes autoimmune uveitis and skin depigmentation
–> Seen in Japanese Akitas and Samoyeds
What common eye neoplasm in cats cause lead to uveitis
Leukaemia lymphocarcoma complex
What tumour can cause intraocular inflammation in the eye and what does this mean for tumour prognosis
Lymphoma
= automatically stage 5
What infectious agents can cause uveitis in the dog
Canine adenovirus
Agents from abroad e.g leishmania, borrelia, ehrlichia
What is different about iridal melanoma in dogs vs cats
Benign in dogs
Often malignant in cats
What may a pink mass appearing through the pupil be
Ciliary body adenoma or adenocarcinoma
What is iris atrophy and what is a differential for is
Acquired condition where iris becomes translucent with irregular pupillary margin and sluggish pupillary light reflex
–> Especially profound in poodles and see holes in iris
Differential = coloboma but this is acquired
Describe the redness seen in an eye with glaucoma (compared to with conjunctivitis)
> Vessels are engorged so looks more red
But no redness between vessels
Because this is due to high pressure in vessels NOT due to cytokines
4 key symptoms of glaucomatous eye
- Red eye: engorged vessels
- Painful eye (acute) with corneal oedema
- Pupil dilation
- Blind eye due to optic disc cupping
How does glaucoma cause blindness
Because pressure forces the optic disc backwards, pushes on lamina cribrosa through which the optic nerve axons pass and kills of ganglion cell bodies
Movement of fluid from production to leaving
Produced by the ciliary body, flows through pupil into anerior chamber, drains through trabecular meshwork to the ciliary cleft and out via drainage vessels
Do we ever get glaucoma due to overproduction of aqueous
No
What specific type of glaucoma is the beagle prone to
Open angle type
Iridocorneal angle is open but the trabecular meshwork is blocked by proteoglycan build up
What tumour can get stuck in the iridocorneal angle
RIng melanoma
Is glaucoma usually primary or secondary in cats
Secondary
- Due to inflammation (uveitis) or neoplasia
What cause of glaucoma are we more likely to see in terriers or border collies and why
Secondary to lens luxation
Due to inherited weakness in the zonule
–> Acute glaucoma
What is iridodonesis
Wobbling of the iris without the support of the lens behind it
e.g in lens luxation where lens then moved posterior
Signs we will see in lens luxation glaucoma
If luxated anteriorly see lens in front of eye
Other signs: iridodonesis (wobbling of iris without lens support), corneal oedema in centre where lens abutted endothelium, aphakic crescent
Which tonometry method is good for very small eyes e.g birds
Tonovet tonometer (= rebound)
How can glaucoma occur secondary to anterior uveitis
Synechiae block movement of fluid through pupil
Inflammatory swelling of ciliary cleft closes angle
Inflammatory debris collecting in and blocking the trabecular meshworm
In what breed can you get blockage of iridocorneal angle due to pigment deposition WITHOUT melanoma
Cairn terrier
How can glaucoma occur secondary to neoplasia
Either by large solid mass blockin the iridocorneal angel
Or neoplastic cells (e.g lymphoma) blocking trabecular meshwork
When do we see ciliary cleft collapse
End stage glaucoma
Tumour
What is the emergency treatment initially done for glaucoma
IV mannitol at 20% 10mg/kg over half an hour
–> To reduce intraocular pressure
3 methods of reducing aqueous production
- Carbonic anhydrase inhibitors (NB: old drugs cause metabolis acidosis)
- beta blockers to constrict the ciliary body
- Surgical reduction: freezing or laser
When are beta blockers useful in reducing aqueous production
In low tension glaucoma e.g 30mmHg BUT we usually get presented with much higher pressures than this
Why is endoscopic laser of ciliary body complex and hard to do (to reduce aqueous production)
Need to remove the lens to get the aqueous in
Why is there a high risk of fibrosis in response to foreign material in the eye e.g in drainage implants
Due to TGFbeta action
What is the unconventional drainage pathway for aqueous and how might we open it pharmacologically
= through ciliary body and is usually opened up in response to prostaglandins in inflammation
- Fluid goes via suprachoroidal spaces to uveoscleral drainage pathway
- We could use PGF2alpha, Latanoprost
WHat are some problems we can face with the vigor drainage implant
- Get secondary prostaglandin mediated production of new aqueous which is full of fibrin
- FIbrin can block the microchannels and stop drainage
If we are doing an eye enucleation do we need to worry about tying off the optic nerve
No
- The vessels on either side of it are small in the dog and cat so will stop bleeding with firm pressure
WHat is limbal flush
See hyperaemia especially visible at the limbus in uveitis because the vessels of the ciliary body are there so when inflamed, cytokines gives hyperaemia
Differentiating conjunctivitis from uveitis simple
Conjunctivits: redness on globe AND eyelid mucosa
Uveitis: redness just on the globe; esp at limbus
In which cause of red eye do we see a constricted pupil and in which do we see a dilated one
Constricted pupil in uveitis
Dilated one in glaucoma
WHich cause of red eye is more liekly to present with serous/mucoid/purulen discharge
Conjunctivitis
- The others just mainly lacrimation
Pain severity of different causes of red eye
Most painful = glaucoma
Then uveitis
Conjunctivitis painfree or mild
Which cause of conjunctivitis could lead to blindness and what type of blindness
Distemper
= central blindness
In which cause of red eye are the aqueous and iris ost affected
Uveitis
What cause of red eye is most likely to present with hypopyon flat layer of pus
Severe uveitis (= from aqueous)
What might cause a sluggish pupillary light reflex and irregular pupillary margins
Iris atrophy
Esp profound in poodles
