Lazy eye

A lazy eye, known medically as amblyopia, is a condition in which one eye – or sometimes both eyes – has reduced visual acuity that cannot be fully corrected with spectacles or contact lenses. It occurs because, during visual development in childhood, the brain fails to process the image from that eye properly or even suppresses it.

The condition usually develops before the age of six, whilst the visual system is still developing. If the brain consistently receives a blurred, double or distorted image from one eye, it may begin to ignore that eye. The eye itself is often anatomically healthy, but the connection between the eye and the brain does not function optimally.

Causes

A lazy eye can have various causes:

• Strabismus: when the eyes are not aligned and the brain suppresses double images by ignoring one eye.
• Refractive error (anisometropia): a significant difference in prescription between the two eyes, causing one eye to provide a much sharper image than the other.
• Visual impairment: for example, caused by a congenital cataract, a drooping eyelid or a clouding of the cornea that obstructs vision in early childhood.
• Uncorrected refractive error: when a child experiences blurred vision for a prolonged period without correction, particularly if both eyes are affected.

Recognition

Parents or carers do not always notice a lazy eye straight away, as young children are not aware that their vision is impaired. Sometimes strabismus is noticeable, or a child may tilt their head, squint or have difficulty with depth perception. Regular eye checks for young children are important for the early detection of amblyopia.

Amblyopia is not caused by a lack of effort or by reading too little, and it does not go away on its own. Early detection and treatment are essential, as the visual system continues to develop until around the age of eight. The younger a child is when treatment begins, the greater the chance that their vision will improve.

Treatment

Treatment for a lazy eye focuses on stimulating the weaker eye and training the brain to use the image from that eye again. Commonly used methods include:

• Glasses or contact lenses: to correct any refractive error or difference in prescription.
• Patching (occlusion): the good eye is covered for a number of hours each day, so that the weaker eye is forced to work.
• Atropine eye drops: sometimes the good eye is temporarily blurred using eye drops, as an alternative to patching.
• Treatment of the underlying cause: for example, surgery for strabismus or cataract removal.

Treatment is supervised by an orthoptist or ophthalmologist, who monitors progress and adjusts the treatment plan.

Prognosis and follow-up

With timely and consistent treatment, the visual acuity of the lazy eye can often improve significantly. Without treatment, the visual impairment usually persists for life and can affect depth perception, reading and, later on, career choices. Even after successful treatment, regular check-ups are advisable, as the weaker eye can sometimes deteriorate again, particularly during puberty.

If you have any symptoms or concerns, please have them assessed by your optician, optometrist or ophthalmologist.