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Amblyopia (Lazy eye)

What is amblyopia?

Amblyopia or lazy eye is an eye condition in which the vision is poor where the best-corrected visual acuity is less than 6/6 to poorer than 6/60 in the absence of any ocular structural abnormalities or disease. Generally, this condition affects one eye and rarely affects both eyes. It happens due to abnormal vision development in the early life (infancy or childhood) from the interruption of normal cortical visual pathway development in the brain. Amblyopia is the leading cause of decreased vision among children, which usually present from birth up to age 7 years.

Prevalence

The prevalence of amblyopia worldwide is approximately 1%–5%.The World Health Organization (WHO) estimates 19 million children less than 15 years of age are visually impaired; of those, 12 million are impaired due to uncorrected refractive errors and amblyopia. Based on a recent study of pre-school children in Malaysia, the prevalence of amblyopia was 7.53%, and 66% of the pre-school children had bilateral amblyopia.

Risk factor & Causes

Certain children are born with amblyopia and others may develop in later childhood. The sensitive period of developing amblyopia is from birth to 6-8 years of age where the most rapid development of the visual pathway. A couple of the risk of having amblyopia is higher in children who were born prematurely, low birth weight than average, developmental disabilities, cerebral palsy, mental retardation, congenital cataract, retinopathy of prematurity, and family history of amblyopia, strabismus (crossed eyes), anisometropia, or isometropia. Smoking, consuming alcohol and drugs during pregnancy increases the risk of a child having amblyopia and strabismus. The common cause of amblyopia or lazy eye includes uncorrected high refractive errors, strabismus, and central visual axis obstruction as well.

Common Signs & Symptoms

Symptoms of amblyopia may be difficult to notice in children. Amblyopia of one eye typically in anisometropic and strabismic amblyopia commonly produces fewer symptoms and mild disability where the patient usually has good visual acuity in the normal eye. The most significant problem in children with amblyopia is having difficulty to tell how near or far the object/something is. This is due to poor depth perception (stereopsis), which reduces the efficient visual performance in their learning process on certain tasks such as cycling and eye-hand coordination during near activities. Besides, parents may notice their child struggling to see clearly and present signs like squinting, closing one eye or tilting their head to see things. Amblyopic children who favour one eye sometimes may have a tendency to bump into objects particularly on one side as well. In addition, children with amblyopia may contribute to the chance of having strabismus on a later onset. An additional problem with amblyopia children is the potential of visual loss in their better eye.

Diagnosis

In most cases, parents don’t know their child has amblyopia until diagnosed by a doctor during an eye examination. This is why it’s crucial for children to have an eye screening at least once as early as the ages of 3 to 5. Early diagnosis increases the peak of a complete recovery. It is recommended for children to have a comprehensive eye examination by the age of 6 months and again at the age of 3. The lazy eyes will not go away on their own and if left undiagnosed until the years of preadolescence, teenager, or adult, the treatment is usually less effective and takes longer.

Treatment

Amblyopia or lazy eye treatment varies including the prescription of lenses, prisms, eye patching, and vision therapy. In vision therapy, patients are encouraged to learn how to use both of their eyes working together, which helps to prevent lazy eye from recurrent.

Prevention

A comprehensive eye examination by the age of 6 months and again at the age of 3 is crucial for a child for early detection of amblyopia or any other ocular disorder.