Baby has one eye smaller than the other: what should you do?

While you are in your own little bubble of happiness, exchanging loving glances with your "mini-me", you notice that your baby has one eye smaller than the other. The questions start flooding in: why? what should you do? is it permanent? and many more besides. Let's stay calm and look for answers together.

A closer look at vision in babies

First of all, let us recap a little on how vision develops in children. Visual development is estimated to take place from birth until around the age of 6. As you know, visual acuity in newborns is very low.

All they can distinguish are contrasts, but barely any faces. However, visual development is very rapid. Very quickly, your baby will begin to see images that become increasingly sharp as the days go by.

It is at around 4 months that your baby will be able to follow faster movements. They will start to distinguish colours. Then, at around 18 months, they will have reached half of their full acuity: that is, 5/10.

Finally, from the age of 6, the child will have reached a visual acuity of 10/10 in each eye. They will have good colour vision and excellent coordination, and therefore very good 3D vision.

It is no coincidence that the acquisition of reading tends to begin at that age.

What if your baby has one eye smaller than the other?

And here comes the parental worry galloping back. But rest assured that in most cases this disappears with age. Often linked to pupillary immaturity and to the fact that maximum development has not yet been reached, this difference will eventually stop existing as your child grows. But what is it linked to? Let us run through the possible scenarios.

Several possible explanations

The most frequent cause is anisocoria. We quite agree that this term does not mean much to most people. Put plainly, anisocoria refers to a person whose two pupils are of different sizes.

This may therefore be at the root of your baby's smaller eye. Another possible cause is what is known as amblyopia, or a "lazy eye".

To put it simply, if your baby has a visual disorder such as a squint, short-sightedness, or indeed long-sightedness or astigmatism, the brain suppresses the image from the most out-of-focus eye.

The child thus gets used to seeing only with the eye that functions best, and neglects the other one, which will not develop its muscles at the same rate.

It should also be noted that hereditary factors may play a role. In all cases, it is best to address this as quickly as possible.

What should you do if you notice that your baby has one eye smaller than the other?

We won't be very original here, as you might expect, but of course you will need to consult your paediatrician. They will assess the situation at their level and, if necessary, refer you to an ophthalmologist to carry out tests on your child — a fundus examination to begin with, for instance.

What does the future hold for your baby's vision?

While it goes without saying that we should keep you informed of these few brief facts about a baby having one eye smaller than the other, we do want to reassure you on this subject: bear in mind that in many cases, as your child grows, the visual issue has every chance of resolving itself.

Looking into it and seeking advice is perfectly logical, but not giving in to panic is better. Stay confident — you are doing the right things, and being here to find out more is very much to your credit!

And as you know, nature is remarkably well designed, and everything will very likely sort itself out.