Hello - I'm touching wood as I type this as it's now a year since the last episode but I haven't felt brave enough to post about this before...
When my Springer was a tiny puppy she had what looked like a kind of seizure: froze in place for a few seconds with her eyes flickering like crazy. This was first thing in the morning after she had been leaping around playing manically. Probably sounds weird but I was so scared at what it might mean (I'd only just brought her home at 8 weeks old) that I managed to convince myself that she was just 'dizzy' from playing and didn't tell anyone about it.
Then it happened again a few weeks later - and then nothing until she was going on for 5 months old when a third episode was witnessed by my OH as well as myself and he convinced me it was definitely abnormal (I know.. I know..) and I took her to the vet. Blood tests showed nothing abnormal but this third episode of nystagmus co-incided with an infection which my puppy had developed in a broken tooth - so possibly it was a seizure of some kind? But this doesn't explain the other two times it happened.
Now a year has gone by with no further 'attacks' but I wondered if anyone else had encountered this before? The vet said that it was most unusual to have nystagmus without any other symptoms. He advised a 'wait and see' approach rather than rushing into having brain scans done - which in retrospect I am glad about.
The only other thing about my girl that worries me is that she doesn't seem to have put on any weight since she was six months old. I changed her food to Burns around the time of her last 'funny turn' and as she has been OK since I am afraid to change it.
I suppose I'm still 'on the alert' in case something is lurking - hope someone can put my mind at rest! :)

When a person has nystagmus this isn't ignored and investigated thoroughly.  I would be asking my vets all of the possibilities (good or bad).  Hope you dog stays well and doesn't suffer from it again.

As the person who has nystagmus, I can tell you it does have many causes and some they are yet to identify.  I don't know too much about your breed but I wouldn't panic too much as it may be a response to over exercising, as it can be with humans, or stress.  It could also be a number of other things. 

Please try not to worry, it doesn't necessarily mean a brain tumor, here I am living proof of that.  With humans it can be symptomatic of episodic ataxia, where the sufferer has nystagmus and becomes clumsy.  By its very nature - episodic - it comes and goes and is exacerbated by raised potassium serum levels in the blood which wont be identified with a routine blood test.

You must speak with your vet if only to put your mind at rest. 

Edited to say

Sorry you have already spoken to your vet and he has told you to keep an eye on things, that is all you can do for the time being.  Has he suggested a change of diet to put weight on.  Working dog brand foods always did it for my dogs with a good helping of minced chicken thrown in.

Thanks, perrodeagua, for your good wishes. :) Unfortunately after the blood tests found nothing my vet couldn't provide me with any answers (although it was suggested to send my then less than 5 month old pup away to a veterinary hospital for brainscans I decided in the end not to put her through that.)
And thankyou echo, that is very interesting - I didn't know that nystagmus could be caused by stress and over exercise in humans. I wonder if there is a canine parallel as my pup was running around wildly shaking a raggy toy/cardboard box when the episodes happened.
You have correctly guessed that I was worried about a brain tumour... in fact I think the vet first suspected that because I was quizzed about possible behavioural changes at the time (that made me really anxious!)
I hadn't heard of episodic ataxia either, and raised potassium levels... I suppose if there are causes still unidentified in humans then there could be even more undiscovered causes in animals...
Thankyou so much. That's a lot of food for thought and it has made me feel a lot better about it all. I am sorry you have to cope with it yourself though - I'd imagine it can't be that easy.
And - yes - I keep wondering about a working dog food as my girl does seem to manage to 'work' herself throughout the day, running everywhere at top speed - perhaps that's what the problem is with the weight. :)

Thanks for your good wishes.  I learned to cope with my problem a long time ago and other than not being allowed to drive it doesn't bother me very much. 

Even with humans they don't have cures for this yet, unless there is an operable tumor - which is certainly not the case with the familial condition I suffer, so it is just a case of managing it.

The thing you have to watch for is any change in temperament when the nystagmus happens, I don't know too much about it but I understand that if the dog becomes aggressive with the nystagmus this should be checked out with your vet. 

Should have added that the nystagmus after exercise, stress etc only happens if the individual is susceptible to the problem, it is also seen in people who are the worse for drink.  I am really cheap to take on an evening out as only one small glass of anything sets my eyes off LOL!

Many thanks for the extra info...
I too am very cheap to take on a night out but have no excuse whatsoever other than being a complete lightweight! :D