Strabismus (sometimes also called ‘squint’ or ‘lazy eye’) is a condition where the eyes do not line up together. This means that when one eye is looking at something, the other one turns in, out, up or down. It can be present all the time or just every now and then. Strabismus usually appears in early childhood and may present from birth.
What are the causes?
Strabismus affects approximately five in every 100 children. There are a number of causes.
In children who are born with strabismus, it can be due to muscles or nerves not developing correctly, but if it appears in the first few months of life, it is usually due to the brain not controlling eye alignment correctly.
Children who have a problem with the focus of their eyes, especially those who are longsighted, can develop strabismus.
Strabismus can also appear after head injuries or illnesses that cause weakness in eye muscles.
How is vision affected?
When the eyes are not straight and working together, each eye sends a different image to the brain. To stop confusion, the brain will sometimes ignore part of the image from one eye.
If one eye becomes dominant, it can lead to a decrease of vision in the turned eye (amblyopia). When the turned eye swaps from one side to the other frequently, then the vision is usually equal.
Strabismus also affects a child’s ability to judge distance which may result in clumsiness and poor hand-eye coordination.
Signs and symptoms
Common signs can include closing one eye, clumsiness, an unusual head position and eyes that look misaligned.
In some children, the strabismus may only be obvious when looking in a particular direction, or when the child is tired or unwell.
However, some symptoms may not be discovered until child is old enough to describe the problem. These can include double or blurred vision and difficulty reading.
How is the condition diagnosed?
It is normal for a baby’s eyes to look misaligned for short periods of time up to the age of four months. Strabismus that is present always, or is becoming increasingly obvious, is not normal and needs to be seen as soon as is practical.
Strabismus can sometimes be a sign of serious eye and health conditions. Early investigation, diagnosis and treatment of strabismus is important in getting the best outcome for the child.
Eye professionals, including ophthalmologists (eye doctors), orthoptists and optometrists, use an assortment of tests to see if a child’s eyes are straight and working together. The eye professional will almost always need to put eye drops into the child’s eyes as part of the complete first examination.
What is the treatment?
Treatment aims to improve the alignment of the eyes and to bring back, or protect, normal vision. Treatment can include glasses, patching, eye drops, eye muscle surgery and eye exercises.
Eye professionals work together to design a treatment plan for each child. In many cases, it will require a combination of treatments.
Last updated: October 2023