Ophth - anterior segment conditions Flashcards
What is the uvea made up of?
The iris, ciliary body and choroid
What are the functions of the choroid?
Supplies nutrients to the retina
Site of blood aqueous barrier and blood retinal barrier (tight junctions which maintain the immune privileged site)
What does the choroid contain?
Tapetum lucidum
What are the different sections of the uvea called?
Anterior and posterior chambers
Where is aqueous humour produced?
Ciliary body
Where does the aqueous humour drain out of?
The iridocorneal angle - through the pectinate ligaments into the trabecular meshwork of the ciliary bodyq
Where does the aqueous humour fill?
The posterior chamber, then flows out of the pupil into the anterior chamber
What is uveitis?
Inflammation of the uvea
Breakdown of the blood aqueous barrier and the blood retinal barrier
What are the main clinical signs of uveitis?
Blepharospasm
Epiphora
Lacrimation
Hyperaemia
Corneal oedema
What are the pathognomic signs of uveitis (if you see these you can diagnose uveitis)?
Keratic precipitates
Aqueous flare
Fibrin
Hyphaemia
Hypopyon
Rubeosis iridis
Swollen iris
Aqueous flare
What is rubeosis iridis?
Hyperaemia of the iris - neovascularisation and vasodilation
The iris appears reddened
Difficult to see in animals with a dark brown iris
What is aqueous flare?
Protein or cells in the anterior chamber that have leaked through the blood aqueous barrier
What effect does aqueous flare cause?
Tyndall effect - scattering of light by particles in a fine suspension causing a sparkly misty effect
What does fibrin look like in uveitis?
Clots into wisps/threads in the anterior chamber
What are keratic precipitates?
Accumulations of WBCs which clump and attach themselves to the cornea causing oedema and cloudiness (endothelium cant pump water out)
What is hypopyon?
Purulent exudate which clumps and settles in the ventral anterior chamber
What is a secondary effect of hypopyon?
This purulent debris can block the drainage angle and cause secondary glaucoma
What is hyphaema?
Blood in the anterior chamber - vessels leak RBCs
Can be free floating or a clot
What can cause hyphaema?
Uveitis
New blood vessels being more friable
Trauma
Glaucoma
Coagulopathies
Tumour
What do iris lymphoid follicles look like?
Black marks around the periphery of the pupil
What are iris lymphoid follicles?
They develop in response to inflammation
Histologically they are B and T cells that have arrived due to antigenic stimulation
What are the clinical signs of chronic uveitis?
Synechia
Hyperpigmentation of the iris
Iris bombe
Glaucoma
Lens luxation
Phthisis bulbi
What are synechia?
Adhesions between the iris and adjacent tissues - can be in the anterior or posterior segments
What are secondary effects of synechia?
Risk of blockage of the drainage angle and secondary glaucoma
What is iris bombe?
When there are synechia attaching the iris to the lens the whole way round
What causes lens luxation?
Inflammation of eye weakens and breaks down zonular attachments
What is Phthisis bulbi?
Chronic low pressure in eye causing globe to shrink and eye to be non-functional
What can cause uveitis?
Trauma
Anaemia
Hypertension
FeLV/FIV
Septicaemia
Endotoxaemia
Diabetes mellitus
Immune mediated
What tests should you do in a uveitis case?
Haem, biochem
Urinalysis
Thoracic radiography
Abdominal ultrasound
What is lens induced uveitis?
Immune mediated
Lens is formed very early - in the first month of gestation
Therefore its lens proteins are hidden from the immune system
Any escape of lens protein is highly antigenic to the eye
This causes profound intraocular inflammation and uveitis
What is the name for a sudden, acute lens induced uveitis?
Phacoclastic (blasts the antigens all at once)
What is the name for a chronic, leaky lens induced uveitis?
Phacolytic
When does a phacolytic lens induced uveitis occur?
When a cateract becomes hypermature over many years of development, the solid opaque lens protein can start to liquefy into smaller molecules that can then cross the intact lens capsule causing uveitis
How do you treat uveitis?
Remove primary cause
Control inflammation
Prevent complications
Relieve pain - analgesia
What can you give to relive pain from uveitis?
NSAIDs
Atropine
Opioids
Topical steroids - pred, dexamethasone
How does atropine reduce pain from uveitis?
Relief from painful ciliary muscle spasm
Mydriasis - reduces synechiae
What are the functions of the lens?
Focuses light onto the retina
Accommodation - near and far
What is lenticular nuclear sclerosis?
Produce lens fibres very slowly throughout life
Therefore lens enlarges very slowly throughout life which causes cloudiness in the nucleus as it gets squashed by new layers
What provides nutrition to the lens as it forms in the foetus?
Hyaloid artery
This regresses once aqueous humour is being produced
What makes the lens transparent?
Soluble protein
No vessels
Few organelles
Fibres regularly arranged
What shape do lens fibres make?
Fibres run from pole to pole and meet at suture lines at front and back of eye - inverted Y shape
What are the 4 main classifications of cateracts?
Incipient
Immature
Mature
Hypermature
What is incipient cateracts?
When less than 15% of the lens is affected
What is immature cateracts?
When there is still a light reflex - can still see the tapetum
What is mature cateracts?
No tapetal reflex
What is hypermature cateracts?
Shrinking
What can cause cateracts?
Inherited
Diabetes mellitus
Senile/old age
Trauma
Lens luxation
Uveitis
What causes diabetic cateracts?
Sorbitol produced from hyperglycaemia being broken down in the aldose reductase pathway
Sorbitol draws water in through the capsule pushing apart the lens fibres
How do you treat cateracts?
Phacoemulsification
No medical treatment - topical NSAIDs
What is lens luxation/subluxation?
When the zonules breakdown and the lens loosens
If they are all broken then the lens is freely floating
What are the clinical signs of lens luxation?
Aphakic crescent
Vitreous prolapse
Anterior or posterior
Cataract
What is an aphakic crescent?
The lens is in front of the pupil so you can see a clear area in pupil around the lens - shouldnt be able to see the edges of the lens
What is a sign that the lens is posterior to the pupil?
Crescent between the lens and the pupil
What can cause lens luxation?
Inherited defect
Trauma
Uveitis
Secondary to glaucoma
What is vitreous prolapse?
Strings of jelly in the aqueous humour
How can you treat lens luxation?
Intracapsular lens extraction - remove whole lens
Phacoemulsification (if subluxation)
Couching - medical
What is couching?
Treatment for lens luxation - lens massaged into posterior segment of eye then construct pupil
