Keep an Eye on Children's Visual Problems

Dr. Agnes TSE

Honorary Consultant in Ophthalmology

Specialist in Ophthalmology

The first 8 years after birth is a crucial period for the development of children’s vision. Visual problems in children are difficult to detect from mere appearance and small children are often unable to verbalise their visual difficulties. Therefore we recommend children to undergo a comprehensive eye assessment at 4 years old. For children younger than 4, if there is any suspicion of eye abnormality, they should be brought to see an eye doctor as soon as possible. This ensures that problem is promptly treated before the condition deteriorates.

Strabismus (Squint): More than about Appearance

Strabismus, also called squint, is a condition in which two eyes look at different directions. One eye looks ahead while the other either turns in (convergent squint), turns out (divergent squint), or up or down (vertical squint). The child will only use the eye which is looking ahead and suppress the other eye. This will lead to loss of stereoscopic vision (3-D vision) and even lazy eye (amblyopia).  Strabismus also affects the appearance of a child and has an impact on his social life.

Strabismus is mostly due to  poor coordination of the brain and eyeball muscles. In a minority of cases, it is secondary to serious eye conditions, such as tumour, cataract, etc. Children with squint should be treated as soon as possible.    

Convergent squint, or crossed eye, occurs when only one eye is pointed at the target and the other looks inwards and therefore suppressed. The most common convergent squints are infantile convergent squint and accommodative convergent squint. Children with infantile convergent squint are usually born with defective brain-eye coordination, and squint is noticeable when they are a few months old. Surgery is recommended before the age of 2. Accommodative convergent squint may arise from long-sightedness, and usually occurs at around 2 to 3 years old.  It can be improved by wearing glasses.

Divergent squint refers to a condition when one eye looks at the target while the other eye looks out. The condition is often intermittent and can be treated by eye exercises or surgery.

Amblyopia may Become Irreversible if Neglected

Vision develops rapidly in the first 8 years after birth. Amblyopia, or lazy eye, may occur if visual development is hindered during this crucial period, resulting in blurred vision which is not correctable by glasses. Risk factors for developing lazy eye include droopy eyelids, congenital cataract, huge difference in refractive errors between the eyes, squint, etc.

For most cases, lazy eye is found in one eye only. There is often no noticeable sign. Therefore parents may not be aware of their children relying only on the better eye to see things. If detected early, lazy eye can be corrected by patching the normal eye. Correction is far less likely if the condition remains undetected until 7 or 8 years old.

Atropine Eye Drops Slow Down Myopia Progression in Children

Another common eye problem in children is myopia or shortsightedness. It is especially prevalent in Asia. Around 40% of primary school children in Hong Kong have myopia, and the progression is most significant in 6 to 12 years olds. Myopia occurs due to elongated eyeballs, which makes the object being focused in front of the retina and causes blurry vision when seeing distant objects. It is considered “high” if in excess of 600 degrees, and is often associated with many serious eye problems, e.g. retinal detachment, macula haemorrhage, cataract, glaucoma, etc.

Atropine is a non-selective muscarinic acetylcholine antagonist extracted from plants. It was first introduced in the 1970s to slow down myopia progression. In the past, atropine eye drops were used in high concentration. It causes pupil dilation and ciliary muscle relaxation, which in turn led to photophobia and blurred near vision. Recent studies show that low-concentration atropine eye drops are more effective at hindering myopia progression with far fewer side effects: 0.5% and 1% atropine eye drops are shown to be able to slow down myopia progression by 75% and 80% respectively. The use of eye drops has to be individualised according to each child’s condition. The treatment has to be monitored by regular eye checks.

The effect of progressive lens in myopia progression remains inconclusive. Introduced in the 1970s, Ortho-K/OK lenses are flat and rigid contact lenses that can decrease the curvature and refractive power of cornea. The downside is that children need to wear retainer lenses at night to preserve the modifications. This carries risk of corneal abrasion, ulcer, infection and even permanent loss of vision.

Viewing Distance and Eye Health

With school suspension during the COVID-19 pandemic, children are now spending most of the time with electronic products at home. For eye protection, parents should make sure that children use the electronic devices properly in terms of screen time and viewing distance:

There is no evidence to prove that blue light-blocking glasses or health supplements can slow down myopia progression. In fact, a healthy, balanced diet is far more important than taking health supplements. Ensure adequate lighting when using electronic products, which should be set at optimal brightness and font size. Also remind your children to blink often to increase tear production, and rest for 20 to 30 seconds after every 20 to 30 minutes of screen time.