Ocular Histopathology Flashcards
(61 cards)
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Normal eye histo
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What is a common feature of corneal oedema?
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- Dehydrated cornea - reduced corneal stromal clefting
- Superficial injuries to the cornea can cause corneal oedema - generally more limited to the area of injury e.g. ulceration
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What is the most predisposing factor of glaucoma?
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Increased intraocular pressure
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What is goniodysgenesis? (2)
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- Cocker Spaniels predisposed (autosomal-recessive condition)
- Associated with defective drainage angle (pectinate ligament never rarified to the point that it should be in development)
- Cause of 1^y glaucoma
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Lens equator - one side more rounded than the other
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What is the process by which the outflow of aqueous humour gets occluded? (3)
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- Inflammation - obscures ciliary cleft
- Neovascular membranes proliferate in response to uveitis (particularly in dog)
- Uveitis leads to secondary glaucoma through synechiae (iris adheres to cornea (anterior)/lens (posterior)
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Diffuse iris melanoma
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Small lymphocytes + plasma cells (lymphocytic + plasmacytic)
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What are the three different patterns of ocular inflammation? (3)
1. Uveitis - inflammatory cells limited to uvea
2. Endophthalmitis - retina (inner layers) + chambers get involved with exudates
3. Panophthalmitis - when all the layers of the eye including tunic and orbit are affected
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Endophthalmitis
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What is a pathognomic lesion of equine recurrent uveitis?
Amyloid + rod-shaped eosinophilic inclusions
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What is is a lesion of equine/large animal glaucoma?
Atrophy of corpora nigra (iris modification)
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What is a morgagnian globule?
Lesion of cataracts - when lens fibres swell + become more distinct + individualised. If identified with a nucleus = bladder cells
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What are two main mechanisms of glaucoma-related corneal oedema and
how do they differ?
* Corneal endothelial injury – generally diffuse
* Exposure keratitis – usually focal/regional
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What is the MAJOR site of injury in glaucoma-related vision loss?
Optic nerve head/lamina cribrosa/inner retina
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Explain how glaucoma and lens luxation are interrelated
Buphthalmia can cause luxation; lens location can cause secondary glaucoma
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What is the most common predisposing factor for glaucoma?
Elevated intraocular pressure/obstruction of aqueous outflow
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Name two sites where aqueous outflow can be impeded
Ciliary cleft; pupil margin (pupil block/iris bombé)
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Name the most common primary feline intraocular neoplasm
Diffuse iris melanoma
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Name two mechanisms by which ocular neoplasia can cause glaucoma
Physical obstruction of aqueous drainage
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How do patterns of glaucomatous retinal damage differ between cats and
dogs?
* Cats: limited to inner retinal atrophy;
* Dogs: Advanced/full-thickness atrophy ventral
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What is the most reliable indicator of chronicity of corneal disease?
Neovascularisation
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Name two mechanisms by which ocular neoplasia can cause lens luxation
* Secondary glaucoma/buphthalmia
* Physical displacement/disruption of zonules
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What is the most common cause of equine glaucoma?
Equine recurrent uveitis
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How does IOP (intraocular pressure) typically change in uveitis? Glaucoma?
Uveitis: Low; Glaucoma: Elevated
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What are the two most common mechanisms by which uveitis leads to
glaucoma?
Neovascular membranes/synechiae; occlusion of outflow by cells/matrix
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How are uveitis and cataract interrelated?
Cataract can cause lens-induced uveitis; uveitis can cause cataract
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Differentiate the distributions of: uveitis; endophthalmitis; panophthalmitis
* Just uvea;
* Uveitis + retina/chambers;
* All layers of the eye (including fibrous/orbit)
