Seminar: The Abnormal Pupil

Question 1

How may cataracts affect the pupil?

Answer 1

-> 2* phacolytic uveitis (phacoleaky) as exudes proteins from the cataract

Question 2

How does posterior synechia appear clinically?

Answer 2

Rough pupil edges

Question 3

How does glaucoma affect the pupils?

Answer 3

• fixed, mid dilated non responsive

+ episcleral pattern

Question 4

How will all causes of retinal atrophy appear eventually?

Answer 4

• hyperlucent/reflective tapetum (one zone only, ratehr than equally reflective as it should be)
• atrophied retinal BVs
• dark optic disk

Question 5

How can ataracts be distinguished from nuclear sclerosis?

Answer 5

• DDO
• cataracts will -> shadow when reflected from behind
• nuclear sclerosis allows light thtough

Question 6

What are iris rests?

Answer 6

• posterior synechia where the stuck on bits break off

- leave a ring/splodgy ring of pigment = iris colour r black around the lens

Question 7

What is the only possible cause of pigment being left in the centre of the pupil?

Answer 7

Persistent pupllary membranes

- pupil doesnt constrict enough to leave pigment in the exact centre

Question 8

What colour are the backs of all irises?

Answer 8

Black

Question 9

Where do iris cysts arise? Why?

Answer 9

• always arise on BACK of iris

- as made of EPITHELIUM, whih is only present on the back (front = stroma)

Question 10

What may occour 2* d/t iris cysts?

Answer 10

> free floating anterior uveal cyst if i pinches off and is carried forward in the aqueous humour
- can fill up nterior chamber and block vision (will sink to the bottom)
golden retrievers and great danes cysts can build up behind the iris and push iris forward -> blockage of the ICA and 2* glaucoma

Question 11

What are the ddx for melanotic growth in the anterior chamber in cats? How cna benign and malignant be distinguished?

Answer 11

• Benign melanosis ->
• Anterior Uveal Melanoma (benign/melignant)
• no way to distinguish benign v. malignant*

Question 12

How cna progression from benign melanosis to AUM (anterior uveal melanoma) in cats be identified?

Answer 12

• very difficult
• look for hanges in surface architecture as well as colour
• look for pupillary changes at rest and with dilation

Question 13

Tx AUM?

Answer 13

• enucleation
• but metastassi uncommon and v slow (happens years later) so sometimes best to leave?
• look at speed of progression and age of patient to decide

Question 14

What sign often correlates with presence of mets in uveal melanoma in cats?

Answer 14

• presence of glaucoma

Question 15

What pupil changes can be seen with AUM?

Answer 15

• slow and sluggish PLR as iris musculature has been affected
• dyscoria (funny shaped pupil)

Question 16

What can be given to diagnostically dilate the pupil?

Answer 16

• Tropicamide (short acting version of atropine)

- doesnt affect ciliary body as much as iris

Question 17

What potential causes can affect PLR?

Answer 17

• synechia
• glaucoma
• PRA
• cysts
• melanoma/cytoma/iridoepithelial adenoma/sarcoma/lymphoma

Question 18

What is the Marcus-Gunn sign? What does it indicate?

Answer 18

• absent direct PLR, and no response in other eye when affected eye tested
• consensual PLR still present when unaffected eye tested
  > indicates damage to retina or pre-chiasmal optic nerve (afferent only)
• retina, optic nerve head, optic nerve

Question 19

Outline the visual pathway

Answer 19

• retina, optic nerve, chiasm, optic tract, lateral geniculate body (brain), optic radiation, cerebral cortex

Question 20

What does menace test?

Answer 20

• vision
• a prechiasmal lesion should have no menace response on affeced side
• NB. do not elicit blink by touching hairs/creating a draft

Question 21

What types of reflex is PLR? Where is the pathway?

Answer 21

Subcortical

• travels sae as visual pathway past chiasm and for a short distance in the optic tract
• pretectal nucleus
• Edinger-WEstfal Nuclei (?)

Question 22

Why is Marcus Gunn sign not seen with unilateral glaucoma?

Answer 22

???

- fixed pupil seen with glaucoma

Question 23

What may affect the PLR that is not of neural basis?

Answer 23

• catecholamine release
• iris problems
• senile iris atrophy (rough jagged edges of iris around pupil)
• posterior synchiae

Question 24

What do post-chiasmal lesions of the visual pathway cause?

Answer 24

• “central blindness” (even though not necessarily in the brain)
• hard to pinpoint location if post-chiasmal

Question 25

How do the visual fields relate to the optic tracts?

Answer 25

• right visual field is detected by left hemisphere in both eyes and is carried as the left optic tract
• left visual field is detected by right hemisphere in both eyes and carried as right optic tract

Question 26

What is hemianopia?

Answer 26

Single optic TRACT affected -> loss of one visual field (not one eye!!)
- NB: will be the opposite visual field to thhe damaged tract

Question 27

Potntial causes of central blindness?

Answer 27

• neoplasia
• MUO/MUE/GME (meningtis or unknown origin)
• post anaesthetic ischaemia (cortical necrosis) in cats
  > if concurrent signs - imaging/neuro consult!!

Question 28

Do anterior uveal cysts block ICA?

Answer 28

No

Question 29

What signs make you suspicious of more malignant melanoma?

Answer 29

PLR and dyscoria

- indicate deeper muscles affected

Question 30

What are the 2 potential causes of an abnormal pupil?

Answer 30

• iris

- PLR pathway