1120hrs Compression optic neuropathy: when "glaucoma isn't glaucoma" - Kimberley Cockerham, MD
/for POAG,
- fam Hx, elevated symm IOP, slow progression but can snuff out near end, classic optic nerve cupping
Cupping of optic nerve NOT synonymous with glaucoma
- wegeners can do it too for example
Need to think of glaucoma as just one of those optic neuropathies
Compressive Optic Neuropathy
- typically no fam Hx glaucoma but still can have
- elevated ASYMMETRIC IOP, but of course if pituitary, can cup OU
Just because lots of red Xs on HRT, does not mean glaucoma
Classic teaching its optic nerve and not brain:
- originates blind spot
- not respect vertical meridian but does respect horizontal
- all these things not exclusive to glaucomatous optic neuropathy
Central scotoma:
- although classic for compressive, she found lots of tumor patients without central defect
Look for warning signs:
Could this be altered outflow?
Listen, look, palpate
- listen for complaints, look with room lights on, palpate eg thyroid, meningioma, CC fistula - can have resistance to retropulsion
Warning signs not glaucoma
- decreased vision
- APD
- colour desaturation
- nerve more pale than cupped
- atypical VF defect
Intracranial problems
- pituitary, meningiomas, other parasellar mass/infiltrate
Orbital problems
- TED, Optic nerve sheathe tumour,/infilration
- orbital tumor (eg cavernous hemangioma)
Gives patient example
- more damaged when first seen 2 years ago than expected for glaucoma
- ordered an MRI at that time which showed a massive pituitary adenoma that was interpreted as normal
Another patient:
- slowly progressive VF defect
- intermittent eyelid puffiness: episcleral outflow to orbit altered
- longstanding ocular migraines - when looked laterally, vision blacked out! this is not ocular migraine
- increased resistance to retropulsion one eye
- MRI showed large ON meningioma; responded to radioTx seven years out now
Another patient with sphenoid wing meningioma shown next
- suspect with pain, numbness, eye movement issues, ache or fullness feeling, loss of vision earlier than would expect for just glaucoma
- 75% such patients have ocular hypertension even in primary gaze
- optic nerve can be normal, have a cavitation, and not have swelling, or other compression signs
Warning signs of altered venous outflow eg CCF:
- retropulsion res, proptosis, temp fulness, eyelid edema, injected vessels
- listen Hx of high BP, valsalva, listen for fistula, look for blood in schlemm's canal
- kind of allergic looking eyes in low flow as opposed to corkscrew vessels
ON can be normal or cupped, can have venous dilation, dot/blot heme, etc
- can see enlarged superior ophthalmic vein on US, CT, MRI
Indications for intervention:
- decreased function, pain, inc IOP, disfigurement
Tx
- embolization techniques (coils, glue, particulate matter)
TED
- note rounding of eyelids may be only finding around eye
- can have raised IOP even in primary position, but remember check IOP in restricted fields of gaze
- optic disc typically normal but cavitation can happen over time
- VF testing, like other compression ON, central scotoma is classic but often other findings....arcuate, step, etc
- ancillary tests: TSI or TSH receptor here, or Thyroid index (at VA hosp)
- indications for decompression:
--> inc IOP, VF loss, etc
So, how to distinguish: check for the warning signs
- could this be compressive optic neuropathy or altered EV flow
- look, listen, palpate
- look at the scan yourself or have someone you trust look at it.