Parents frequently notice that their baby's eyes do not always appear to move together in the first weeks of life. Understanding when intermittent eye crossing is a normal feature of early visual development and when a squint requires prompt professional assessment is important, because the consequences of a missed or late-treated squint — amblyopia (lazy eye) — are preventable with early intervention but become increasingly difficult to treat as the child gets older.
Healthbooq supports parents with guidance on normal visual development in infancy and the signs that warrant referral for ophthalmological assessment.
Normal Visual Development in the First Weeks
The visual system of a newborn is immature in ways that include limited acuity, restricted range of focus (optimal focal distance is approximately twenty centimetres — the distance to a carer's face during feeding), and incompletely coordinated eye movements. In the first six to eight weeks of life, brief, intermittent crossing or wandering of the eyes is common and reflects the immaturity of the ocular motor control system rather than a fixed squint.
This transient newborn eye crossing typically involves brief episodes where the eyes drift inward or outward momentarily before realigning. It is not constant, does not persist when the baby is alert and focused, and resolves as the visual system matures. Parents often notice it in the first two to four weeks and may be alarmed, but it is a normal feature of early infancy.
What a Squint Is
A squint (strabismus) is a persistent or consistent misalignment of the visual axes of the two eyes. One eye may deviate inward (esotropia — the most common type in children), outward (exotropia), upward (hypertropia), or downward. The deviation may be present all the time (constant squint) or intermittently, or it may alternate between the two eyes.
True squint is distinct from pseudosquint — the appearance of a squint due to prominent epicanthal folds (the skin folds at the inner corners of the eyes that are normal in some ethnicities) causing the whites of the eyes to be less visible on the nasal side. Parents often worry about pseudosquint; the corneal light reflex test (shining a light at the face and observing whether the reflection is centred symmetrically in both pupils) helps distinguish true squint from pseudosquint.
Why Squint Requires Early Treatment
The visual system develops through a "critical period" in early childhood, during which the brain requires balanced, high-quality visual input from both eyes simultaneously to develop normal binocular vision and optimal acuity. A squint interrupts this process because the brain receives conflicting images from the two eyes (one looking straight, one deviated) and resolves the conflict by suppressing the input from the deviated eye. If suppression is sustained, the visual cortex fails to develop normal sensitivity to input from the suppressed eye — this is amblyopia (lazy eye).
Amblyopia, once established, causes persistent reduced vision in the affected eye even when the mechanical cause (the squint) is treated. The degree of amblyopia that develops and its treatability depend strongly on the age at which treatment begins: before the age of approximately seven to eight years (the end of the critical visual development period), amblyopia is substantially treatable; after this age, treatment becomes less effective.
Assessment and Treatment
Any squint that persists consistently after eight weeks of age should be referred for ophthalmological assessment — this can be initiated by a GP or health visitor. The UK newborn and infant physical examination (NIPE) includes eye examination at birth and at six to eight weeks specifically to identify squint and other ocular pathology.
Assessment involves testing visual acuity (in young children, using preferential looking tests), the corneal light reflex test, cover testing (occluding each eye in turn to identify deviation), and fundal examination. Treatment depends on the cause and type of squint. Refractive errors (short-sightedness, long-sightedness, or astigmatism) causing squint are treated with glasses, which may resolve the squint entirely or prepare the visual system for further treatment. Amblyopia is treated by patching the stronger eye or using eye drops to blur it, forcing the brain to use the weaker eye and develop its visual cortex. Surgical correction of the muscle misalignment is performed when residual squint persists after optical treatment.
Key Takeaways
A squint (strabismus) — misalignment of the eyes — in a young child requires prompt assessment to prevent amblyopia (lazy eye), which develops when the brain suppresses the visual input from the misaligned eye. Intermittent, brief eye crossing is common and normal in the first six to eight weeks of life as the visual system matures. Persistent or consistent squint after eight weeks should be assessed by a GP. Squint is treatable, and the treatment — glasses, patching of the stronger eye, and sometimes surgery — is most effective when started early, before the critical period of visual development closes at around seven to eight years.
