The Uveal Tract & Glaucoma

Question 1

what are the 3 categories of developmental abnormalities?

Answer 1

incomplete development
maldevelopment
incomplete regression of embryological tissue

Question 2

what is the arrangement of the iris sphincter muscle in the dog and in the cat?

Answer 2

dog: circular
cat: longitudinal

Question 3

describe the blood supply to the iris

Answer 3

long posterior ciliary arteries and anterior ciliary arteries, which lead
to the major arterial circle.
Venous return is via the anterior
choroidal circulation.

Question 4

describe the blood supply to the ciliary body

Answer 4

ciliary body is mainly through the major arterial circle of the iris.
Venous drainage is via the anterior choroidal veins to the vortex veins.

Question 5

what are the 5 layers of the choroid?

Answer 5

1. The suprachoroideae (outside)
2. Large vessel layer
3. Medium vessel layer (also contains the tapetum lucidem where present)
4. Choriocapillaris
5. Bruch’s membrane (inside)

Question 6

describe the blood supply to the choroid

Answer 6

short and long posterior ciliary and anterior ciliary arteries.
Venous drainage
is via the vortex veins.

Question 7

what is the significance of the anterior aspect of the iris having no epithelium?

Answer 7

in conditions of chronic intraocular
disease (e.g. anterior uveitis), fibrovascular proliferation may occur uninhibited whereby the fibroblasts and new vessels from the iris stroma do not have to penetrate an epithelium, as would be required at other sites of fibrovascular proliferation within the eye.
Pre-iridal fibrovascular membranes (PIFMs) are a major cause of reduced
aqueous humour drainage and subsequent secondary glaucoma in cats and dogs.

Question 8

what makes up the blood-aqueous barrier?

Answer 8

tight junctions in the non-pigmented ciliary body epithelium,
the pigmented posterior iris epithelium
the non-fenestrated blood vessels of the iris

Question 9

what is the aim of ocular immune privelege?

Answer 9

minimise excessive intraocular inflammation and therefore preserve ocular 
function and prevent irreversible damage to the very delicate structures within the globe

Question 10

what are the 3 basic events of inflammation of the uvea?

Answer 10

increased blood supply
augmented vessel permeability
white blood cell migration

Question 11

give 4 examples of immune-privilege mechanisms of the eye

Answer 11

blood-ocular barrier
aqueous humour composition (namely ascorbic acid and other antioxidants)
anterior chamber associated immune deviation (ACAID)
a lack of intrinsic lymphatic system.

Question 12

what is the main differential when considering iris to cornea PPMs, anterior segment dysgenesis and Peter’s anomaly?

Answer 12

penetrating corneal trauma

Question 13

what is the main differential diagnosis when considering iris-to-lens PPMs?

Answer 13

posterior synechiae

Question 14

what is the main differential diagnosis when considering PPM remnants?

Answer 14

iris rest

Question 15

give 12 signs specific to uveitis

Answer 15

Photophobia
Aqueous flare 
Anterior chamber cells
Anterior chamber fibrin
Keratic precipitates
Hyphaema*
Hypopyon
Iris swelling
Rubeosis iridis (iris neovascularisation)
Iris nodules**
Miosis***
Reduced intraocular pressure

Question 16

what virus can cause uveitis in dogs?

Answer 16

Infectious canine hepatitis (CAV-1)

Question 17

what is the most common primary intraocular tumour in the dog?

Answer 17

melanoma

Question 18

name 3 viruses that can cause uveitis in cats

Answer 18

Feline immunodeficiency virus (FIV)
Feline leukaemia virus (FeLV)
Feline infectious peritonitis (FIP)

Question 19

what is the most common intraocular tumour in cats?

Answer 19

diffuse iris melanoma

Question 20

what are the 3 main variants of feline post-traumatic ocular sarcoma?

Answer 20

1. The spindle cell variant is the most common; it is more often associated with lens damage and shows the most invasive behaviour.
2. A round cell variant of FPTOS may actually
   represent a variant of lymphoma.
3. Osteosarcoma and chondrosarcoma are less
   frequently encountered.

Question 21

true or false: unconventional pathway comprises approximately 3% in dogs and 15% in cats of total aqueous outflow

Answer 21

false: 3% cats, 15% dogs

Question 22

give 4 ways intraocular neoplasia can induce glaucoma

Answer 22

1. Direct involvement of the drainage angle in the neoplastic process
2. A build-up of neoplastic cells from the aqueous within the trabecular meshwork
3. Secondary blood–aqueous barrier breakdown, leading to debris within the trabecular meshwork
4. Stimulation of fibrovascular membrane formation as a result of the release of angiogenic substances

Question 23

give 5 possible side effects of systemic carbonic anhydrase inhibitors

Answer 23

Potassium depletion
Metabolic acidosis
Diuresis
Anorexia
Gastrointestinal disturbances (vomiting and diarrhoea