pupils sometimes different sizes but dr. couldn't find it!

I happened to notice the other day that my pupils sometimes are different sizes, (my eyes were irritating me so I was examining them) in the dark or in a darkened room. In the light they are usually the same.  I don't know how long I have had this, so I have no idea if it's a new thing or I have always had it.
I don't have any other symptoms. I am a woman, 35.  I am 6 months pregnant, if that makes any difference.

I went to an opthamologist today and he couldn't find it or see it! He did an hour long exam, with drops, turned on and off the lights etc.  I don't understand why he couldn't see it.  I made the mistake of asking him what could cause this and there are a lot of scary things that could or it could be "just the way I am!"  I looked it up on the internet and it could be a brain tumor.

I am very concerned about a lesion or neurological problem. He has referred me to a neuro, I will see him in three days.

[John C Hagan]

Since your pupil dilates "sometimes" you may not have had the problem when you were in to see the neurologist. Please use the search feature on this page and search pupil problems. You are on the right track seeing the neurologist. Most of the times the cause of this pupil problem is not a brain tumor, often it is a completely normal reaction for some people. Up to 10% of people have unequal pupils some always some at times this is called anisocoria.

JCH MD Eye Physician and Surgeon

[Cthycarlson]

I have not yet seen the neuro. I saw the opthamologist and he said my exam was normal. Would this have ruled out something like Horner's syndrome?  I read that that can be a cause of unequal pupils. My left pupil does not dilate as fast as the right and doesn't get as big. Also, I swear my upper eyelid droops a bit though my husband tells me my eyes have always been like that.

[Di878]

The past four days my right eye felt irritated like something was in it.  Upon closer look I noticed that the pupil in the right eye was bigger than the left eye. I have a feeling of  some pressure in that eye and slight pain in the temple area but no other symptoms.  Should I  be concerned

[John C Hagan III, MD, FACS, FAAO]

Yes, sudden onselt of dilated pupil is potentially serious.

JCH MD