The Abnormal Pupil

Question 0

When do abnormal uveal cysts become a problem?

Answer 0

If they are too numerous as they remain behind the iris, pushing it forwards, closing the ICA causing glaucoma
They disturb the patient causing fly catching behaviour

Question 1

Where is the problem?

Answer 1

In the iris

In the PLR pathway

Question 2

What happens if anterior uveal cysts are left untreated?

Answer 2

Breakdown of the cyst and a splotch of pigment is left in the endothelial side of the cornea or the anterior lens capsule
Doesn’t interfere with sight unless numerous or thick

Question 3

What can lead to anterior uveal melanoma in cats?

Answer 3

Benign melanosis

Question 4

When does the change from benign melanosis to anterior uveal melanoma (AUM) occur?

Answer 4

Look for changes in surface architecture not just colour
Look for pupillary changes at rest with dilation
Presence of changes in architecture makes it suspicious and pupillary changes confirms diagnosis

Question 5

What is the treatment for AUM?

Answer 5

Enucleation

Metastasis is uncommon and occurs years later so look at speed of progression and age of patient when making a decision

Question 6

What else can PLR abnormalities be caused by?

Answer 6

Synechia
Glaucoma
PPM
Anterior uveal cysts
Extraocular polymiositis

Question 7

What is the visual pathway?

Answer 7

Eye -> optic chiasm -> optic tract -> lateral geniculate body -> optic radiation

Question 8

What response would a pre-chiasmal lesion have to menace and PLR?

Answer 8

Menace - no menace response on the affected side
PLR - no direct PLR in affected side or indirect from affected side but will have normal direct in unaffected side and a normal indirect from the affected side

Question 9

What is a Marcus Gunn sign?

Answer 9

Prechiasmal, unilateral afferent lesion
Retina/optic nerve head/optic nerve
Not unilateral glaucoma as would not have indirect PLR in affected eye

Question 10

What other factors can influence the PLR?

Answer 10

Catecholamine release
Senile iris atrophy
Posterior synechiae

Question 11

What happens if the lesion is post-chiasmal?

Answer 11

Central blindness
More difficult to pinpoint after cross-over of fibres
If with other clinical signs arrange neuro consult or imaging for neoplasia/GME/MUO/MUE/post anaesthetic ischaemia (cats)

Question 12

What does GME stand for?

Answer 12

Granulomatous meningal encephalitis

Question 13

What does MUO stand for?

Answer 13

Meningitis of unknown origin

Question 14

What does MUE stand for?

Answer 14

Meningitis of unknown aetiology

Question 15

What is the difference between a mild form of PPMs and posterior synechiae leaving iris?

Answer 15

Location as iris rest = ring, PPM = centre

Question 16

Is benign melanosis easy to differentiate from melanoma in the anterior uvea of cats?

Answer 16

No look for surface changes or dyscoria

Question 17

What is the result of a lesion affecting the left optic tract?

Answer 17

Left visual field loss