Lazy eye is also known as amblyopia, which refers to poor vision due to incomplete visual development within the brain. The expression “lazy eye” is therefore inaccurate – the eye is not working less hard, but rather the image that it captures is not being used by the brain.
Overtime, the brain will ignore the images received from the “lazy eye” and become increasingly reliant on the other eye.
Amblyopia affects about 1 in 30 children and can be difficult for parents to notice. Most cases are actually alerted during eye screening tests conducted in preschool. At home, a parent may be able to spot if there’s lazy eye is if there’s squinting, or the child fusses over one eye, or the child cannot see, or very resistant when you ask him to see with one of his eyes only.
Causes of Amblyopia
Broadly speaking, anything that interferes with clear vision in the eye between birth and 8 years of age can cause amblyopia. This is the period where visual pathways are being developed. The common causes are:
1. High myopia, hyperopia or astigmatism in one eye – if the high myopia (short-sightedness), hyperopia (long-sightedness) or astigmatism in one eye is not corrected, the image from this eye is blurred. Overtime, the brain will ignore the blurred image from this eye.
2. Strabismus, also known as squint – this refers to misalignment of one eye where one eye is off to the left, right, up or down. The turned (squinting) eye becomes less dominant overtime.
3. Blockage in one eye – this can be due to droopy eye lid or childhood cataract. It may also be a blood clot or scar that blocks the vision of one eye.
A family history of amblyopia is also a risk factor.
Symptoms of Amblyopia
Depth vision is affected by amblyopia, thus one symptom is poorer hand-eye coordination for fine tasks like threading a needle or when judging distance during a ball game. Another symptom is a smaller peripheral vision as both eyes are not working together. Blurred vision, double vision and squint are also symptoms.
Treatment of Amblyopia
Amblyoia is treated by first tackling the cause of it. If it is abnormal spectacle power, spectacles have to be prescribed to correct the myopia, hyperopia or astigmatism. These spectacles have to be worn at all times. For children with strabismus, the squint can be corrected by surgery. Similarly, there are surgery options for cataracts and droopy eye lid.
After treating the cause, the brain needs to be encouraged to use the image from the lazy eye. This is done by having the child wear a patch to cover the good eye. The hours to wear per day and duration to do so is prescribed by the doctor, and instructions have to be followed diligently. It is also often advised to do close-up activities while wearing the patch. Often, several hours per day is prescribed and the treatment is more effective when started earlier. Recent studies have shown that lazy eye can still be improved when treated during early adulthood or teen years.
An alternative to wearing an eye patch is putting atropine eye drops. These eye drops dilate the pupil of the good eye so that the vision captured from it will be blurred. The brain may then choose to use the image from the lazy eye. However these eye drops may not work for every child, and can cause eye irritation and headache.
An alternative and less conventional treatment is optometric vision therapy where specific exercises are prescribed to train the lazy eye. Acupuncture may also work (based on a study from a Chinese university) although the mechanism is not clear. It is possible that acupuncture increases the blood flow to the brain and the eye, and stimulate nerve growth.
Detecting amblyopia early is critical as long periods of the brain ignoring the images captured by the “lazy eye” can become permanent. The first few years of childhood are also critical years when visual pathways are developed and thus most effective to treat amblyopia. If you notice any of the symptoms or have been advised by the nurse to follow-up with eye consultation, it is important to consult an eye doctor promptly.
