Enlarged pupil in one eye

Hi,

I've recently noticed that one of my pupils (that of my right eye) is at times larger than the pupil in my left eye.  I've had 'issues' with this eye for approximately 5 years, whereby I see flashes of white light in the peripheral some days its all the time other days its non existent.  I've seen my doctor about this and I've had a full examination of the eye (albeit a few years ago now) and there was nothing untoward, I've also had an MRI scan of the brain to check there is nothing the matter here either and thankfully it came back clear (that was mid 2005).  

You can see a very slight difference in the size of the pupil when in a brightly lit room, but it is most noticable when you are in a dimly lit or dark room.  I would say it is approximately 2-3mm larger than the other eye.  The eye does react to a change in light also, so it seems normal but there is just a significant difference in the size of the pupils.

I was happy to just 'plod along' as I was until I've noticed this change in my pupil.  I cannot say when it's changed but I first noticed it a couple of weeks ago.  I am a worrier so this is playing on my mind alot at the moment any suggestions would be appreciated.

Thanks

[Michael J Kutryb, MD]

Could be physiologic anisocoria, adies tonic pupil, horner's syndrome or third nerve palsy.  Look for associated symptoms like droopy eyelid, or eye turned out and not moving properly.  Physiologic anisorcoria fits  your stated symtoms (symptoms) best (worse in dim light, nearly normal in regular light, no droopy lid or loss of eye movement.)  I cannot, of course, make your diagnosis without seeing you.  Watch out for associated abnormally large pupil, droopy eyelid and loss of eye movement or eye turning out - possible signs of very serious third nerve palsy.  I recommend you see neuro-ophthalmologist.  He/She can make your diagnosis without difficulty.  Good Luck.

MJK MD