18 answers

Pupil Dilation in One Eye

I noticed tonight that my son's right pupil was dilated. He is almost 6 months old. There has been no difference in behavior, i.e. eating, sleeping, temperament.
Has this happened to you? Should I be concerned? I looked online but they give you the scariest scenarios or worst case scenarios.

1 mom found this helpful

What can I do next?

So What Happened?™

So after his nap, he got up and they were back to normal! I called my dr and will keep an eye on it over the weekend. If it happens again, I will be taking him to the ER. If not, he will be getting a checkup on monday morning. Thank you, thank you to all who took the time to respond. I appreciate all of you!

More Answers

How much different is the dialation in the right eye versus the left eye? If it is severe/fully dialated then you should probably take him in the his doctor. If it is just mildly different this can be normal. Mild dialation of one pupil versus the other can occur in children under one year of age from muscular weakness in that eye. The eye is trying to focus on objects, faces, etc and might not be focusing as well as the other eye is from this muscular weakness. Does your son also tend to lean/tilt his head to one side more than the other?
There are ways to strengthen these eye muscles with exercises. If you go see you regular doctor and find out everything is normal, you should come see me and we can work on creating exercises to help strengthen these muscles.
I am a chiropractor whose daughter has this condition and it is helped by getting her adjusted (removing nerve interference from the spine) and doing exercises to strengthen the weak eye muscles.
My office number is ###-###-####.

It could be Anisocoria which is basically one pupil larger then the other. My son has that. He gets checked once a year by Dr. Stager Jr who I absolutely love! His number is ###-###-####.
Definitely take him to see an Ophthalmologist to have it checked out.

seek immediate medical attention. It is a neurological symptoma dn a red flag in the medical cummunity. On adults it is a sign of a stroke. God bless you and your son.


Definitely take him in to get it checked out. Most likely its neurological in nature and needs to be evaluated. It could be something very simple that needs just to be monitored to something more serious that if caught early the outcome would be much better. If your pedi doesn't have an answer, ask for a referral to a pediatric neurologist for a consult. Don't let this go undiagnosed and/or treated.

I think you need to take your son in asap. It may be nothing but you do not want to wait and see its something that needs immediate care.

I would get that checked out ASAP. good luck

Are you positive that it's different than the other eye? I would call the doctor's afterhours number and ask her what to do. Hopefully it's nothing, but with these things, you can't be too careful. Please call, and feel free to message me with what they say.

For what it's worth, I'm a nursing student, set to graduate in 9 months, and I would call ASAP just to be safe.

Good luck,

Edit to add: Yes, at 6 months old, maybe he fell backwards (still unsteady sitting up) or something and hit his head. I would probably take my son to the ER too, but I don't want to panic you. Just call the doctor right now.

One of my son's eyes would sometimes dilate more than the other. I took him to the dr. Nothing. It would just happen at random times. This went on for about 6 months & then that same eye started to "drift" just barely...so minimal that only I initially noticed it. Took him to an opthamologist and it turns out my child has VERY poor vision in that eye requiring glasses. I WISH I had thought of an opthamologist earlier so that my child could have really SEEN the world he had been in. This dr couldn't explain the dilation either but I thought it was all just more than a coincidence. Hope all turns out well for you.

I would take him immediately to the doctor. If you live near Flower Mound, there is a wonderful pediatric after hours/weekends clinic called A-Cute Care. It is awesome!

Hopefully it's nothing! But since it could be something very, very serious, get it checked out immediately! ER to rule out a head injury, but follow up with pediatrician who would know more about childhood issues than an ER doc who deals with acute trauma and not long term issues.

This is definitely a question for your doctor...ASAP. I'm sure it will turn out to be nothing but why take the chance?

Good luck,


My hubby is a nurse and said you need to take him to the ER right away. It could be something like a mild concussion, but there are many other things that would need to be ruled out as well and could be much more serious. Good luck! Let us know how it goes!

Hi A.! Being an eye doc it is a little unusual to have just one pupil dilated in an infant. I don't want to alarm you but I would sure have it checked out. If the pupils are relatively close in size and both react normally to light then he may just have phsiological anisocoria (normal pupil differnce); however, if it is something new then you definitely want to rule out clotting in the brain or something compressing the pupil fibers (tumor). Get him to ER ASAP if you notice an eye suddenly turning in or out. Best of luck!!

Call your pedi imediately. It is not normal for one of his eyes to be dilated. Does it stay that way? Has he taken a fall at some point? Hit his head in any way? Call the pedi today and describe what's going on.. . if nothing else, he's fine and you've checked. but don't let it go unchecked!

Definitely call your doctor's emergency number or take him to the ER! My son who is now 21 had this happen and it was some sort of concussion although he hadn't jarred his head that we knew of!

Hi A.

That same thing happened to me. I know your baby is 6 months old but it freaked me out. I went to my eye doctor and he said I probably just touched something that got in my eye and caused the pupil to dilate. Said nothing to worry about. I do hope that helps.


My now 14-year-old daughter used to have one eye that was more dilated than the other. I first noticed it when she was a baby, and the doctor said it was nothing to worry about. Until I read your post I hadn't thought about it in years, so it must have become more normal at some point, but I don't know when. Just check with the pediatrician at your son's next visit.

Run, do not walk to a pediatric ophthalmologist, or the nearest emergency room. Pupil dilation in only one eye can mean a brain bleed, serious head injury or even a vision problem. Do not sit on this one!!!! I was an ophthalmic tech for 10+ years. If you shine a bright light in that eye and it doesn't constrict, you have a problem. Either optical or neurological, either way, do not hesitate one more second to get help.

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