Ophthalmology 3 Flashcards by Brooke Phillips

Define…
1. Uveitis.
2. Glaucoma.
3. Cataract.
4. Phakic.

Inflammation of uveal tract.
Ocular neuropathy with high Intraocular pressure.
Opacity of the lens (or lens capsule).
‘Of the lens’.

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Define…
1. Anterior uveitis.
2. Posterior uveitis.
3. Panuveitis.
4. Phthisis bulbi.

Inflammation of the iris +/- ciliary body (iridocyclitis).
Inflammation of the choroid (chorioretiniris).
Inflammation of iris, ciliary body and choroid.
End stage shrunken globe (chronic uveitis).

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What is the uvea (uveal tract)?

Iris, ciliary body, choroid.
Vascular layer of eye.
- aqueous humour secretion.
- nutrition globe contents.
- immune function — protects delicate cells / preserves clarity.
- accommodation of lens.
Blood aqueous barrier.
Blood retina barrier,

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What do both the anterior and posterior chambers contain?
- what segment of the eye are both these chambers in?

Aqueous humour.
- anterior segment.

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Ophthalmology techniques for inside the globe.

Direct observation with light source.
Distant direct ophthalmology.
Close direct ophthalmology.
- anterior (+5D to +20D).
- posterior (+0D).
Distant indirect ophthalmology.

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What do the signs of uveitis all result from?

Breakdown of blood aqueous barrier and blood retinal barrier.

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Acute clinical signs of uveitis.

Miosis.
Keratic precipitates.
Aqueous flare.
Fibrin I’m anterior chamber.
Hyphaema.
Hypopyon.
Reduced IOP.
Iris neovascularisation (rubeous iridis).
Swollen iris.
Photophobia.

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Chronic clinical signs of uveitis.

Iris lymphoid follicles (Intraocular mass).
Cataract.
Synechiae (adhered Iris).
Ectropion uveae.
Iris bombe.
Secondary lens luxation.
Secondary glaucoma.
Iris hyperpigmentation.
Phthisis bulbi.

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Non-specific clinical signs of uveitis.

Blepharospasm.
Epiphora.
Lacrimation.
Chemosis.
Conjunctival and episcleral hyperaemia.
Corneal oedema.
Ciliary flush.
Vascularisation.
Pain.
Reduced vision.

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What can rubeosis iridis lead to?

Vascular endothelial damage > break down of BAB > exudation into aqueous humour / anterior chamber.

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What is iris bombe?

When posterior synechia form around pupil margin 360 degrees and obstruct aqueous escape through pupil so the Iris bulges forward like a balloon due to trapped aqueous. Prognosis poor.

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How do you distinguish which vessels are hyperaemic in a red eye?

Conjunctival hyperaemia give fine branching vessels that continue to the limbus to supply surface of eye.
Episcleral congestion gives deep straight vessels which stop before the limbus to supply the uveal tract, signifying Intraocular disease.

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Differentiating uveitis and glaucoma.

IOP low for uveitis, high for glaucoma.
- normal = 10-25mmHg.
Typical pupil size smaller (miosis) for uveitis, larger (mydriasis) for glaucoma.
Still have vision but reduced with uveitis, blind with glaucoma.

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VITAMIN D causes of uveitis.

Vascular.
Infectious.
Trauma / toxic.
Metabolic.
Inflammatory / idiopathic.
Immune-mediated (lens-induced).
Neoplastic.
Degenerative.
Reflex uveitis.

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What is reflex uveitis?

Can occur secondary to a corneal ulcer (ulcerative keratitis). Antidromic stimulation of corneal nerves induces the release of neuropeptides/cytokines at the other end of the nerve, which act directly on the vascular endothelial and smooth muscle and activate inflammatory cells. Need to treat uveitis as well corneal ulcer for 100% resolution of the issue.

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Lens embryology.

Lens proteins are hidden from immune system
Optic stalk develops thickens darea which goes on to form lens. This placode thickens, invaginates and then forms a vesicle, specific layers go on to become the nucleus, cortex and capsule of the lens.
Lens nutrition in development is initially from the hyaloid artery that runs from the optic nerve to the lens and forms a net around the lens (‘tunica vasculosa lentis’).
Once aqueous humour is produced from developing ciliary body, vessels recede before eyes open at around 2 weeks old in dogs. After this, remnants of the vascular system would be abnormal and may cause cataract or even bleeding with the lens (Persistent hyperplastic primary vitreous / Progressive hemifacial atrophy).

Two types of lens-induced uveitis.
- what do they mean?

Phacolytic - leaky lens, chronic, hyper mature cataract.
Phacoclastic - sudden acute fracture, trauma or bursting e.g. acute diabetic cataract, cat claw injury.

Investigation of uveitis where no obvious exogenous cause.

Haematology (complete blood count).
Serum biochemistry.
Urinalysis.
Thoracic radiography.
Abdominal ultrasonography.
+/- ocular ultrasound.
PCR/sampling for infectious/parasitic diseases e.g FeLV/FIV/FIP/toxo/neospora.
Ocular ultrasonography.

Uveitis treatment principles.

Remove primary cause if can be identified.
- remove lens material / close corneal perforation.
- ABX / antiviral / anthelmintic tx.
- anti-hypertensives.
- chemotherapy/radiotherapy/surgery/dental.

Control inflammation - NSAIDs.
Prevent undesirable complications e.g. synechiae / glaucoma - atropine — relieve pain of ciliary spasm, dilate pupil to reduce risk of Synechiae and therefore iris bombe and resultant glaucoma less likely.
Relieve pain - analgesia — NSAIDs, opioids, atropine (not in face of glaucoma).

Tx must be prompt and aggressive to maintain vision in affected eye(s).
Weaning of tx must be gradual to ensure rebound uveitis doe not occur as tx withdrawn.

How should the lens appear on distant direct ophthalmology.
- exception.

100% clear.
- slight opacity, normal in older animals — senior nuclear sclerosis.

What factors contribute to lens transparency?

Lens crystallin proteins largely soluble.
Lens fibres have very few organelles.
Lens fibres very regularly arranged and interdigital carefully to reduce light scatter.

Best ophthalmoscopy technique for cataract classification diagnosis.

Distant direct.

4 main classifications of cataract.

Incipient = cataract occupies less than 15% volume of the lens.
Immature = can still see tapetal reflex through the cataract (Y shape of suture lines highlighted).
Mature = no longer able to see tapetal reflex.
Hyper mature = leakage of lens proteins causes shrinkage and lens capsule wrinkling, along with phacolytic uveitis.

Causes of cataract.

Inherited = juvenile, early/late onset, senile.
Secondary to other disease e.g. uveitis, lens luxation, PRA toxins (progressive retinal atrophy), diabetes mellitus.
Trauma e.g. radiation, nutritional, electrocution.

Process of diabetic cataract formation.

Patient is hyperglycaemic > glucose diffuses in > increased glucose overwhelms hexokinase pathway > metabolism is shunted to Aldose reductase pathway > end product is sorbitol = large molecule > trapped sorbitol causes osmotic draw > swollen cataract > potentially water clefts along suture lines.

Cataract treatment available.

No medical tx available. Phacoemulsification. - Requires intensive medical support post op. - Risks of persistent inflammation / secondary glaucoma. - Financial cost, frequent meds post op, lifelong meds. - Patients do regain vision. Topical NSAIDs recommended if surgery not appropriate.

Lens luxation/subluxation clinical signs.

Aphakic crescent - space between pupil and lens edges. Zonule loss. Iris or lens wobble. Anterior or posterior.

Lens luxation causes.

Inherited zonule defects - previously in terriers. Severe trauma e.g. RTA, blunt trauma to the head. Uveitis (chronic, severe). Chronic glaucoma.

1. Consequences of lens luxation. 2. Investigation of lens luxation. 3. Treating lens luxation.

1. Acute glaucoma (lens stuck in front of eye and causing obstruction to drainage). Uveitis. Cataract (lack of nutrition as not in right place). 2. DNA test inheritance, referral ophtho exam. 3. Surgical lentectomy (intracapsular lens extraction or phacoemulsification. Medical couching and prostaglandin analogue to keep the pupil small and hold the lens in place.

Ophthalmoscopy techniques to examine the fundus.

Close direct (mag +0D) or distant direct

1. Normal appearance of fundus and back of the eye in most dogs. 2. Normal appearance of the fundus and back of the eye in young dogs (up to first vaccine). 3. Normal appearance of the fundus and back of the eye in blue-eyed dogs.

1. Yellow-green tapetum, with non-tapetal fundus, visualise optic disc and some retinal vessels on top. 2. Blue tapetum which grows and should be reflecting back yellow-green by 10-12 weeks. 3. Lack of pigmentation at back of eye so redness and choroid vasculature.

Progressive retinal atrophy.

Early Blood vessels deteriorate due to cell death and atrophy of retinal cells through life. Hyperreflectivity as retina thinner. Nyctalopia (night blindness). Non painful.

Investigation and diagnosis of retinal issues.

Examination by ophthalmologist. DNA testing. Electro retinography (ERG) -- reduced trace. Colourimetry PLR.