RecruitingObservational

Investigating the root cause of strabismus in children

Strabismus (also known as squint or crossed eyes) is a common childhood eye disorder where the eyes cannot align to look at the same object. Current treatments, such as surgery or glasses, are not always effective, which suggests that the underlying cause may not be fully addressed. One possible explanation is that some children may have inaccurate oculoproprioception — the sense of eye position provided by the muscles that move the eye. This study aims to test whether oculoproprioception is impaired in children with a specific type of strabismus, Partially Accommodative Esotropia (PAE), compared with children whose strabismus is purely due to visual factors (Fully Accommodative Esotropia, FAE) and healthy children without strabismus. By doing so, we aim to establish whether oculoproprioceptive dysfunction could be a root cause of strabismus. Who can participate? Children with a diagnosis of PAE or FAE (recruited from the NHS) who have not had surgery of the extraocular muscles, as well as 4- to 5-year-old children with longsightedness, and without strabismus.

At a glance

Status

Recruiting

Sponsor

University of St Andrews

Enrolment target

102

Start

13 Aug 2025

Estimated completion

30 Apr 2028

Strabismus (squint or crossed eyes), specifically Partially Accommodative Esotropia (PAE) and Fully Accommodative Esotropia (FAE).

What is this study about?

Imagine your brain has a special sensor that tells it exactly where your eyes are pointing, even when your eyes are closed. This sense is called 'oculoproprioception'. This study is trying to understand if this special sense of eye position might be a problem for children who have a squint, also known as crossed eyes. A squint means the eyes don't look in the same direction at the same time.

We know that squints are common in children, and treatments like glasses or surgery don't always fully fix the issue. This suggests there might be something else going on. Our researchers believe that for some children, their brain's ability to accurately sense eye position might not be working as well as it should. If we can confirm this, it could open the door to completely new and more effective ways to help children with squints.

By comparing children with different types of squint to children with healthy eyes, we hope to find out if this 'eye position sense' is indeed a root cause of the condition. While this study isn't testing a new treatment directly, the information we gather could be really important for developing better treatments for children with squints in the future.

Key takeaways

Researchers are investigating if problems with 'eye position sense' cause squints.
The study involves one visit to the University of St Andrews for about an hour.
Children will take part in two simple eye-based tasks in a dark room.
You, as the parent, will be with your child at all times and can stop at any point.
This research aims to find better treatments for squints in the future.

Who may be eligible?

This study is looking for children aged 4 or 5 years old. The researchers are particularly interested in children who have been diagnosed with a specific type of squint called Partially Accommodative Esotropia (PAE) or Fully Accommodative Esotropia (FAE).

They also need healthy children who don't have a squint to compare against the children with squints. It's important that all children in the study wear glasses if needed to correct long-sightedness, and that they haven't had surgery on their eye muscles before.

Children won't be able to join if they have certain other health conditions affecting their brain or nerves, or if they've had eye muscle surgery in the past. Parents must also be able to give informed consent, and the child should be able to understand and agree to take part.

Could this study suit you?

Answer these quick questions to see if you may be eligible. This is a guide only — the research team makes the final call.

Is your child aged 4 or 5 years old?
Does your child have a specific type of squint called PAE or FAE, or do they have healthy eyes?
Does your child wear glasses for long-sightedness (if needed)?
Has your child *not* had surgery on their eye muscles?
Can your child understand and agree to take part (with your consent)?
Do you speak English?

Answer every question to see your result.

What does participation involve?

If your child takes part, you will come to the University of St Andrews for one session, which will last about one hour. Firstly, the researcher will explain everything about the tasks to you and your child using simple words and videos.

Your child will sit on your lap with their chin resting comfortably while they do two simple tasks in the dark. If your child wears glasses, they will be asked to take them off. In the first task, your child will use buttons to move a picture of a butterfly on a screen so it looks like it's straight in front of their nose. In the second task, they'll look straight ahead at a target that appears and disappears, while a special camera records their eye movements.

During these tasks, you might be asked to gently and briefly press on your child's eyelid near the corner of their eye – never directly on their eyeball. You will be fully trained beforehand to make sure you can do this safely and gently. You will be with your child the entire time, and you can stop participating at any point if you or your child wishes to. After the tasks, your child will be offered a fun lab tour and can choose a book and a science kit as a thank you.

Potential risks and benefits

There are no direct, immediate health benefits for your child from taking part in this study, as it's not testing a new treatment. However, your child's participation will help scientists learn more about squints, which could lead to better treatments for children in the future. As a thank you, children will receive a book and a science kit. The main potential risk is the inconvenience of travelling to the university. Tasks may also cause tiredness, or some children might be uncomfortable in the dark. You can stop the tasks or take breaks at any time. The gentle eye press, done by a parent, could cause discomfort if not done correctly, but parents will be carefully trained, and the process will be monitored to ensure safety. You are free to withdraw your child from the study at any time without giving a reason.

Locations (2)

University of St Andrews
Approximate
St. Andrews, Scotland
Children Orthoptic Unit, NHS Fife
City only
Dunfermline, Scotland

Common questions

What is a 'squint'?

A squint, or crossed eyes, is when someone's eyes don't look in the same direction at the same time.

Why is this research important?

This research could help us understand the root cause of squints, which might lead to better treatments for children in the future.

What will my child have to do?

Your child will play some simple games in the dark, like moving a butterfly on a screen or looking at targets, all during one visit to the university.

Will my child get any medication or new treatment?

No, this study is about understanding squints, not testing new medications or treatments. There are no interventions in this study.

Who is running this study?

The study is led by the University of St Andrews, working with NHS Fife, and funded by the UK Medical Research Council.

How to find out more

Daniela Balslev

eye.research@st-andrews.ac.uk +44 (0)1334 462097 Official trial record

Always speak to your GP or specialist before deciding to take part in a study.