Ethambutol Toxicity
S Akky
note asking for a colour vision test and field examination. She had
previously had a biopsy on a suspected tubercule on her neck, but results
were negative, however she had been given ethambutol 400mg/day (not clear
wether this was from her GP or the hospital).
After four months (presumably unmonitored) use, she had noticed a loss of
vision, especially temporally on both sides. This was reported to the GP
who referred her to hospital.
This patient had been seen by one of my colleagues last year and at the
time was prescribed bifocal glasses (about +1.50 right and left, add
+2.00)resulting in VAs of 6/6.
On examination, there was no significant change in Rx, but VAs were down to
(R) 6/36 and (L) 6/48. Ophthalmoscopy revealed normal looking discs (C:D
0.3 OU, NRR flat, Healthy colour, margins clear) but there were many
microaneurysms seen on both maculae.
Throughout the examination, she had difficulty reading the test chart, only
seeing the central letters clearly. Colour vision screening (Ishihara
plates) revealed the same symptoms i.e. only the left sides of the plates
were visible with the right eye and the right sides with the left eye.
However, what she could see was normal (unfortunately no other colour test
was available that may have picked up tritanomoly).
Field screening was difficult due to the threshold being so low that the
brightest stimulus was used for suprathreshold testing and no defect was
found. Unfortunately the bright stimuli would have masked any shallow
defects that may have been present.
The only ocular side effects that I have heard of with this drug are
retrobulbar neuritis and (rarely) some forms of macular degeneration. Has
anyone heard of any field defects associated with this drug?
She reports a bi-temporal hemianopsia which as far as I knew normally would
result from central chiasmal compression most commonly a pitutary adenoma.
All feedback would be greatly appreciated.
--
"Finish each day and be done with it. You have done what you could.
Some blunders and absurdities no doubt crept in; forget them as soon
as you can. Tomorrow is a new day; begin it well and serenely and
with too high a spirit to be encumbered with your old nonsense."
Ralph Waldo Emerson
Andrew Bender (spot)
"S Akky" <NOSp...@TheMoment.Com> wrote in message
news:Xns920FE90357D2Ebi...@130.133.1.4...
be helpful in this case. Since the patient is TBC negative. Consider
diascontinuing ethambutol. spot
> result from central chiasmal compression most commonly a pitutary adenoma.
>
> All feedback would be greatly appreciated.
>
> --
> "Finish each day and be done with it. You have done what you could.
> Some blunders and absurdities no doubt crept in; forget them as soon
> as you can. Tomorrow is a new day; begin it well and serenely and
> with too high a spirit to be encumbered with your old nonsense."
this case.
>
> Ralph Waldo Emerson
>
Zeek
Zeek
"Andrew Bender (spot)" <sp...@snip.net> wrote in message
news:3ce7...@snipnews.snip.net...
S Akky
"Zeek" <zee...@pacbell.net> put finger to keyboard and typed...
> Huh, I didn't know Emerson had any eye expertise.
>
> Zeek
Just my sig, good quote - only way I can face the day ;)
Back to the serious matter,
>A pituitary adenoma is possible as you point out . A MRI
>would be helpful in this case. Since the patient is TBC negative.
>Consider diascontinuing ethambutol. spot
She has already stopped taking ethambutol, MRI was clear, it has been a
couple of weeks now, and vision is still poor - just continuing to monitor.
No sign of optic nerve problems, just the macular reaction and the patient
still subjectively reports the field loss - I'm stumped on this one.
--
"Finish each day and be done with it. You have done what you could.
Some blunders and absurdities no doubt crept in; forget them as soon
as you can. Tomorrow is a new day; begin it well and serenely and
with too high a spirit to be encumbered with your old nonsense."
Ralph Waldo Emerson