Microtropia (slightly inward or outward turning eye)

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Orthoptic Department

What is this information about?

This information is about microtropia. It explains: 

• what microtropia is 
• what causes microtropia 
• why it may not be obvious that a person has microtropia 
• how microtropia may affect your child’s vision 
• what treatment we may give your child if they have microtropia 
• things that may cause your child’s microtropia to worsen and what to do if you think this has happened. 

Why have I been given this information?

You have been given this information because your child has been diagnosed with microtropia.  

Reading this information will help you to know what to expect from the condition and any treatment your child may have for it.

What is microtropia?

A microtropia is a very small strabismus. When someone has a strabismus, it means that their eyes are not pointing in the same direction and are not working together. 

In microtropia a person’s eye usually turns very slightly inwards (towards their nose). In some people the eye may turn outwards (away from their nose) but this is rare. 

What causes microtropia?

Some people have microtropia which is present at birth (congenital microtropia). Other people may get it as a side effect of treatment (such as glasses or an operation) for a larger strabismus. 

Your orthoptist will talk with you about what they think may have caused your child’s microtropia. 

My child’s eyes appear to be straight. Does this mean that they do not have microtropia?

People’s eyes are only very slightly mis-aligned if they have microtropia. It’s not usually possible to tell that they have microtropia just by looking at them. 

An orthoptist or optician does special tests which allow them to tell if someone has microtropia (diagnose microtropia). 

Will microtropia affect my child’s ability to see?

People who have microtropia will often have slightly worse vision in the affected eye. Usually this is only by between one and two lines on the letter chart.   

This happens because the light coming into the eye falls slightly away from the most sensitive part (the fovea) of the back of the eye (the retina). When the light falls on this less sensitive area a person’s vision is slightly reduced. 

How much a person with microtropia’s vision is affected is different for everybody. 

Does microtropia affect 3D vision?

Patients with microtropia often do not have such good 3D vision as those without the condition. The amount of 3D vision that may be affected is also different for everybody. 

Will my child need to wear glasses?

People with microtropia often need a different glasses prescription (they have a different refractive error) in one eye compared to the other. This is called anisometropia. 

If the orthoptist thinks your child has microtropia, they will arrange for them to have a refraction test (glasses test). If this test shows that your child does have anisometropia which is likely to affect them much we will prescribe glasses for them. These will correct their anisometropia. 

Might my child need treatment for any other conditions related to their microtropia?

Your child may have reduced vision (amblyopia) in their affected eye.  

We can usually treat this effectively in children up to the age of 8. If your child is older than this the treatment may not work as well. Your ophthalmologist will advise you about this. 

In people who we think will benefit from treatment we may treat amblyopia by giving them an eye-patch or putting eye-drops into their better seeing eye. This is called occlusion treatment and can improve the vision in the weaker eye. 

Both treatments aim to improve overall vision, but they are not a cure for microtropia.  

Children with microtropia are likely to always have some difference in vision between the two eyes even after treatment.  

The orthoptist will: 

• guide you about the aim of treatment for your child 
• suggest when treatment should stop because there is unlikely to be further benefit from having it.  

Will my child need an operation for their microtropia?

No. Microtropia makes such a small difference to how the eyes are aligned that there is no need to operate. An operation would not improve your child’s vision, including their 3D vision.

Are there any tings which might cause microtropia to get worse?

For most people their microtropia and symptoms stay the same (they remain stable). Sometimes microtropia may get bigger in size (decompensate). This usually happens after a person has been ill or stressed.  

• In adults and children over 5 years this can result in symptoms such as double vision (diplopia). 
• In younger children their vision may get worse quickly. 

If you feel your child’s strabismus has changed, please contact your ophthalmologist.

My older child’s eyes appear to have misaligned recently. The orthoptist tells me the problem has been there for a long time. How is this possible?

Sometimes older children are sent to the eye clinic with what seems to be strabismus which has only recently appeared. When we do tests and checks, we may find that a child has had microtropia for a long time but that it has recently decompensated. This makes it easier to notice. 

People may have microtropia for many years without it being diagnosed. They may have microtropia without any symptoms that are easy to notice. The symptoms may only be found when they have an eye test. 

Who I can contact if I need further information or support after I have read this information?