Toddler Squint and Eye Tests: When Eyes Get Checked

What a squint is

The NHS defines it plainly: "a squint, also called strabismus, is where the eyes point in different directions. It's particularly common in young children, but can happen at any age." One eye may turn in, out, up or down while the other looks ahead, and it may be constant or come and go.

The reason it matters is not cosmetic. The NHS says treatment "is usually recommended to correct a squint, as it's unlikely to get better on its own and it could cause further problems if not treated early on."

When to get advice

The NHS gives four triggers:

• your child has a squint all the time;
• your child is older than 3 months and has a squint that comes and goes — in babies younger than this, squints that come and go are common and are not usually a cause for concern;
• you have any concerns about your child's vision, including "regularly turning their head to one side or keeping one eye closed when looking at things";
• a squint or double vision develops later in life.

A GP, health visitor or local optician service can refer to an eye specialist. The NHS adds one further reason not to leave it: a squint can occasionally be a symptom of retinoblastoma, a rare childhood eye cancer, so a child with a squint should be seen to rule that out.

Why waiting matters

The NHS explains what an untreated squint can lead to: persistent blurred or double vision; a lazy eye, "where the brain starts to ignore signals coming from the affected eye, so your child does not develop normal eyesight"; and embarrassment or low self-esteem.

Its most important sentence is about timing: "surgery can help improve the alignment of the eyes even if a squint has been left untreated for a long time, but any vision problems may be permanent if they are not treated at a young age." The window for developing vision in a young eye does not stay open indefinitely.

The American Academy of Pediatrics makes the same case for screening generally: some eye problems have no symptoms at all and are only found by testing, and "some eye problems can cause permanent vision loss if left untreated in childhood."

What causes a squint

The NHS says the exact cause is not always known. Some people are born with a squint, others develop one later, and it sometimes runs in families. In children a squint is often the eye trying to overcome a vision problem — short-sightedness, long-sightedness, or astigmatism, where the front of the eye is unevenly curved. Rarer causes include some infections such as measles, some genetic conditions, developmental delays, cerebral palsy and other problems with the brain or nerves.

How it is treated

The NHS lists four treatments. Glasses, which help if the squint is caused by an eyesight problem such as long-sightedness. Eye exercises for the muscles that control eye movement. Surgery, which moves those muscles so the eyes line up, and may be recommended if glasses alone are not fully effective. And injections into the eye muscles, which weaken them so the eyes line up better, though the effect usually lasts less than three months.

If a child has a lazy eye as a result of the squint, the NHS says that may need treating first, usually with a patch over the unaffected eye to improve vision in the affected one.

When children's eyes are checked anyway

The NHS sets out the routine points:

• Within 72 hours of birth, as part of the newborn physical examination.
• At 6 to 8 weeks, a follow-up examination for anything not picked up earlier.
• Around 1 year, or between 2 and 2 and a half, when you may be asked about any concerns as part of your child's health and development reviews, with eye tests arranged if needed.
• Around 4 or 5 years old, vision screening soon after starting school, which checks for reduced vision in one or both eyes. This does not happen in all areas; if your child's vision is not checked at school, the NHS says to take them to a local optician.

Free NHS sight tests are available for children under 16 and for young people under 19 in full-time education. The NHS is clear that you do not have to wait for a scheduled check: "speak to a GP or go to an opticians if you have any concerns about your child's vision at any stage."

The AAP describes a similar schedule and adds that from around 1 to 2 years, instrument-based screening devices may be used, and that visual acuity screening — matching letters or symbols from a set distance — is recommended at 4 and 5 years and in cooperative three-year-olds.

What the tests involve

Nothing that requires a child to read. The NHS describes the red reflex test, in which light shone into the eyes should reflect back red; the pupil reflex test, checking that pupils shrink in response to light; attention to visual objects, where an interesting object is moved to see whether the eyes follow; picture or symbol charts for children who cannot yet recognise letters; range of movement tests, where attention is drawn to an object moved to eight positions to test the eye muscles; and a refraction test to check whether glasses are needed.

The AAP notes that if a child fails a vision screening they are usually referred to an eye doctor experienced with children, and stresses following that up even if you have not noticed a problem yourself. A full examination usually includes dilating the pupils with drops.

Other eye things worth mentioning

Not every eye worry is a squint. Persistent watering, a sticky or red eye, light sensitivity, an eye that looks different in size or shape, a white rather than red reflection in flash photographs, or a child who sits very close to screens all deserve a look. The HSE has separate advice on sticky eyes in babies and toddlers, which are usually caused by a blocked tear duct or an infection and are generally minor — but the same principle applies: if you are unsure, ask, because eyes are one of the few areas where early is measurably better than late.