The Abnormal Pupil Flashcards
When do abnormal uveal cysts become a problem?
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
Where is the problem?
In the iris
In the PLR pathway
What happens if anterior uveal cysts are left untreated?
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
What can lead to anterior uveal melanoma in cats?
Benign melanosis
When does the change from benign melanosis to anterior uveal melanoma (AUM) occur?
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
What is the treatment for AUM?
Enucleation
Metastasis is uncommon and occurs years later so look at speed of progression and age of patient when making a decision
What else can PLR abnormalities be caused by?
Synechia Glaucoma PPM Anterior uveal cysts Extraocular polymiositis
What is the visual pathway?
Eye -> optic chiasm -> optic tract -> lateral geniculate body -> optic radiation
What response would a pre-chiasmal lesion have to menace and PLR?
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
What is a Marcus Gunn sign?
Prechiasmal, unilateral afferent lesion
Retina/optic nerve head/optic nerve
Not unilateral glaucoma as would not have indirect PLR in affected eye
What other factors can influence the PLR?
Catecholamine release
Senile iris atrophy
Posterior synechiae
What happens if the lesion is post-chiasmal?
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)
What does GME stand for?
Granulomatous meningal encephalitis
What does MUO stand for?
Meningitis of unknown origin
What does MUE stand for?
Meningitis of unknown aetiology
