The Opaque Eye Flashcards
What does white/ yellow deposits in the eye suggest?
Lipid Calcium, Abscess/ Infiltrate, Scar/ Fibrosis
What does Blue in they eye suggest?
Corneal Ulcer, Vascularisation (leaky vessels), Intraocular disease e.g. Uveitis, Glaucoma
What does abnormal brown/ black pigment in the eye suggest? (5)
Mechanical irritation
Sequestrum (common in cats- piece of cornea died off and taken on a brown discoloration)
Pigmentary Keratitis
Melanoma
Foreign Body
Clotted Aqueous humour and brown spots in the iris are a tell tale sign of what?
Perforation
Why is the healthy cornea transparent?
no blood vessels, myelinated nerves or pigment
What four diagnostic tests can we use to test for Corneal Disease?
- Schirmer Tear Test
- Fluorescein for ulceration
- Seidel Test for perforations
- Cytology- for bacteria
What is healing process in the epithelium layer of the cornea?
How long does it take?
Enlargement and sliding of epithelial cells occurs in the first 1-2 hours
Then they undergo Mitosis to heal- this takes 1-2 weeks for completion
If the Corneal stroma becomes damaged- how long does it take to fully heal and why?
Can take weeks to months to fully heal as it needs to form new collagen fibres and lamellae
How long does it take the corneal endothelium to heal and why?
weeks- months > endothelial cells have a limited capacity for Mitosis so instead they enlarge in size, reduce in number and lose their hexagonal appearance
Blood vessels and Vascularisation heal at a rate of …
0.5mm a day
What is SCCED?
Spontaneous Chromic Corneal Epithelial Defect- on top of the stroma, the HAZ layer stops the epithelium from sticking down onto the stroma hence why it appears as if layers of the cornea are peeling
What is Descemetocele?
surrounding corneal oedema around an ulcer
Can we use Fluorescein to diagnose a Descemetocele?
Fluorescein stain is absorbed by the water-soluble corneal stroma but not the Descemet’s membrane, giving a descemetocele its characteristic “green donut” appearance
What is a Melting/ Malacic Ulcer?
Enzymes from the hosts inflammatory cells break down the cornea so it ‘melts away’
Very very fast process- can happen in hours sometimes
Which breeds are predisposed to Melting Ulcers?
Brachycephalic
How is Immune mediated superficial punctate keratitis diagnosed?
What does a positive diagnosis look like?
Microscopy/ Ophthalmoscopy- appears as circular lesions/ little dots
Which breeds are predisposed to Immune mediated superficial punctate keratitis?
Shetland Sheepdog and the long-haired Dachshund
How do we treat Immune mediated superficial punctate keratitis?
With Steroids or Octocyclosporin
What is Corneal crosslinking?
Uses UV light to strengthen the cornea in cases of corneal degradation
What is Tarsorrhaphy?
surgery to join the eyelids together to allow them to heal- like a see through bandage on the lens
What are some of the reasons that a non ulcerative eye disease isn’t healing? (4)
Mechanical irritation
Infection
Malacia (melting)
SCCED
How is Eosinophilic Keratitis diagnosed?
Cytology- the only eye disease that shows the presence of eosinophils
What species does Eosinophilic Keratitis affect?
Cats and Rabbits ONLY
What is the centre of the lens made from?
Proteins (nucleus)
What tells us the lens is unstable? (4)
Decreased transparency
Phacodenesis (wobbly lens)
Iridodonesis (wobbly iris)
Aphakic Crescent (clear crescent shape in the pupil where the lens has moved out the way)
How do we diagnose problems in the lens?
Usually done via clinical appearance
Also Tonometry may be used to look at high IOP
What is a primary cause of Lens Luxation?
Genetic mutation found in terrier breeds
What is a secondary cause of Lens Luxation? (5)
Chronic Uveitis (due to zonular degradation)
Glaucoma (stretches the zonules)
Cataract
Trauma
Intraocular Neoplasm
What is a Ciliary Zonule and how does this relate to Lens luxation?
The suspensory ligament that connects the lens of the eye to the ciliary body- any damage to this leads to lens luxation
In what order does Aqueous fluid flow?
Ciliary Body > Pupil > Iridocorneal Angle (aka drainage angle)
What is the blood aqueous barrier and how does this suffer during disease?
the barrier in the ciliary body and iris which separates the eye from systemic circulation- can become leaky when inflamed leading to components of the bloodstream entering that shouldn’t be there- e.g. aqueous humour flare, hyphaema, hypopyon
How do we diagnose disease in the anterior chamber of the eye?
Clinical Signs
Tonometry (decreased IOP)
What are Vitreal Opacities?
Floating objects inside the vitreous body
Apart from Liquefaction, what are the other causes of Vitreal opacities? (7)
Persistant Hyaloid Artery
PHPV
Vitreal Degeneration
Haemorrhage
Vitritis
Asteroid Hyalosis
Synchysis Scintillans
What is a persistent hyaloid artery and how does this affect the vitrous?
runs from the disc to the lens- causes local changes of eye background leading to retinal detachment
What is PHPV?
(aka PHTVL)
Peristant Hyperplastic Primary Vitreous- developmental anomaly of the eye due to failure of the embryological, primary vitreous and hyaloid vasculature to regress
Causes persistent cataracts & is unusually untreatable
Vitritis is _______ and commonly occurs alongside _________?
Inflammation of the Vitreous
Alongside Uveitis
What is Asteroid Hyalosis, and what does it appear as?
Another form of Vitral degeneration
Appears as ‘stars’ in the eye that jiggle when the eye moves and then fall back into place
How does Synchysis Scintillans differ from Asteroid Hyalosis?
Like asteroid hyalosis but the vitrous is more liquefied so the ‘stars’ do not fall back into place
What are some common signs of Acute Glaucoma? (5)
Corneal oedema due to high pressures pushing fluid in
Episcleral Congestion
Epiphora (excessive tears)
Mydriasis (dilated pupil)
Absent menace response due to loss of vision
What are some signs of Chronic Glaucoma? (4)
Similar signs to acute as well as…
Haab’s stria (breaks in Descemet’s membrane)
Buphthalmia (enlarged eye)
Lens subluxation (stretching of the globe) leading to Lens Luxation
Optic nerve head cupping (collapses due to high pressures)
What is Gonioscopy?
Eye test that checks for signs of glaucoma- Uses a slit lamp to evaluate eye drainage angle- if the drainage angle is blocked or closed it could be due to glaucoma
What is the first line of defence to manage Glaucoma?
Carbonic Anhydrase Inhibitors- ability to reduce the secretion of aqueous humour, thereby lowering the intraocular pressure
What else can we use to treat Glaucoma apart form carbonic anhydrase inhibitors?
Prostaglandin Analogues- increasing the uveoscleral outflow to reduce IOP
