Microtropia

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This leaflet is intended to answer some of the questions of patients or carers of patients diagnosed with Microtropia under the care of University Hospitals Sussex NHS Foundation Trust.

What is microtropia?

A microtropia is a very small strabismus. Strabismus is the term used to describe eyes that are not pointing in the same direction and not working together.
In microtropia the eye usually turns very slightly inwards (towards the nose) or in some rarer cases very slightly outwards (away from the nose).

What causes microtropia?

In most cases it is a congenital condition meaning it is present at birth. In some patients, microtropia may be present as a result of other treatment for a larger strabismus, i.e. glasses or surgery. The orthoptist can explain how this relates to you.

Why do my child’s eyes look straight?

A microtropia is such a small deviation that it is usually impossible to see just by looking at a person. Only specialist tests which are done by your orthoptist or optician can determine if a microtropia is present.

Will it 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 fovea. This is the most sensitive part of the retina (back of the eye). Because the light falls on a slightly less sensitive area of the retina the vision is slightly reduced. How much vision is affected will vary from person to person.

Will it effect 3D vision?

Quite often patients with microtropia will have poorer 3D vision than those without the condition. As with vision, the amount of 3D vision which is affected will vary from person to person.

Does my child need to wear glasses?

There is evidence to suggest that people with microtropia often have anisometropia.
This means that the refractive error (glasses prescription) is different in one eye compared to the other.
If the orthoptist suspects a diagnosis of microtropia they will arrange for your child to have a refraction (glasses) test. If significant anisometropia is found it will be corrected by prescribing glasses.

Is there any other treatment?

If vision is affected in a child under 8 years of age with microtropia then occlusion therapy can be prescribed to try and improve the vision in the weaker eye. The orthoptist will discuss this option with you if it is necessary.
Children with microtropia are likely to always have some difference in vision between the two eyes even after occlusion therapy but the orthoptist will guide you as to the aim of treatment and suggest when you should stop.
In children over 8 years occlusion may or may not be considered as it can have some risk factor. The orthoptist will decide if it is safe to offer the treatment. In children, surgery is usually delayed until 6 or 7 years of age when results are likely to be better. Any reduced vision should be treated before surgery is considered.

Will my child need an operation?

No. Microtropia is such a small deviation that there is no need to operate. Operating would not improve vision or 3D vision.

Will it change?

Usually microtropia remains stable but in some cases, usually following a period of illness or stress, the microtropia can “decompensate” which means it can increase significantly in size.
This can result in symptoms such as double vision in children over 5 years or adults.
In younger children the vision may deteriorate rapidly.
If you feel your child’s strabismus has changed please contact the orthoptist.

My older child’s eyes have recently misaligned but the orthoptist tells me the problem is longstanding. How is this possible?

Sometimes older children are referred to the eye clinic with what appears to be a new onset of a strabismus. When investigated thoroughly it may become evident it is in fact a longstanding microtropia which has decompensated. It is not uncommon for microtropia to go undiagnosed for many years since there are often no noticeable symptoms unless your child has an eye test.