Amblyopia (Lazy Eye)

Amblyopia is the main cause of visual impairment in children starting at early childhood. It is the result of poor vision in an otherwise perfectly healthy eye. Reason for this is because of reduced visual input in one eye during visual development throughout infancy to early childhood. The reduced visual input in one eye is because the eyes and brain are not communicating with each other and the brain
starts to favour one eye over the other, this is known as ‘lazy eye’.

A child’s vision starts developing form birth. At first, a new born’s vision is quite poor but as a child grows and visual stimulus continues to enter their eyes, their vision improves significantly. By age 5, a child should be able to visibly focus at all distances. From this age, the visual system starts to develop by associating visual stimulus from life events. Complex neural networks between the eyes and the brain are being formed to create the child’s sense of reality.

This process is carried out until 9 years old. A consequence of this is that it is tough to treat and improve the vision in any child over the age of 9 with diagnosed amblyopia.
 For that reason, it is critical that if you suspect your child has poor vision that they should be seen, observed and treated before 9 years of age by an eye care professional.

Cause(s) of Amblyopia

Glasses prescription for one or both eyes (nearsighted, farsighted or astigmatism)
Strabismus (eye turn)
Nystagmus (shaky eyes)
Ptosis (droopy eye lid)
Congenital cataracts (born with a cloudy lens)

Amblyopia is difficult to detect, mainly because your child will not complain of blurry vision. The best way to detect the presence of amblyopia is to get your child screened regularly at an early age by an eye care professional. Symptoms may include the following:

Continually shuts/squints/rubs one eye
Complain they ‘can’t see’ when one eye is covered
An eye is turned (in/out/up/down)
A white pupil (easily spotted in flash photography)
An eye(s) that shake constantly
Tilted head posture
Poor depth perception

Risk Factors
Small size & low weight at birth
Premature birth
Family history of lazy eye
Developmental disabilities

Treatment of amblyopia involves making the child use their weaker eye (lazy eye) more frequently. This is carried out by making the child wear a patch over the stronger eye up to 2 hours a day (this could be more depending on severity of amblyopia). 

Different approaches to the patch involve the use of eye drops, wearing filtered glasses and changing the glasses prescription. All these methods are used to stimulate vision in the weaker eye and help the brain’s visual centres develop more completely.

Strabismus is a visual condition where both eyes are misaligned and point in different directions. Amongst children, strabismus is a quite a common condition that affects about 4% of all children in Australia. This condition is also known to appear in adults, which can result in double vision. 

Misaligned eyes, present as one eye fixating on a target while the other eye turns either, in, out, up or down. When this happens, two different images are sent to the brain, resulting in short-lived double vision, in response the brain starts to reject the image from the misaligned eye to eliminate this double vision. Consequence of this clever process is that visual development of the misaligned eye is halted and the child’s ability to participate in normal recreational and school activities is compromised.

It is known that the eye turn can switch between both eyes, where either eye can fixate on a target. Strabismus presents itself typically between 3-4 years old but can also occur from as young as 6 months old. 

Strabismus Classification: 

Esotropia – one eye turns inwards

Exotropia – one eye turns outwards

Hypertropia – one eye turns up

Hypotropia – one eye turns down

Causes of Strabismus

Nerve Palsy
There are six important muscles around the eye that control the eye’s movement. These muscles are supplied by numerous nerves. If ever, these nerves become damaged, it blocks the signal to activate a specific eye muscle to move into its full range of motion. Typical causes of nerve damage are in new borns that have experienced a traumatic birth and or have developmental issues with the brain centre that controls eye movements.

Eye Muscle Restriction
Occasionally, one of the six muscles around the eye can become trapped or damaged. This limits the amount movement the eye can make and could result in the good eye to look misaligned in certain positions to compensate for the bad eye’s muscle restriction. While muscle restrictions can be acquired form birth, it is more commonly present in people with injury(s) to the eye or an over-active thyroid.

Developmental Issues
A child with developmental delay from common conditions such as Down’s syndrome or cerebral palsy has established numerous affects associated with strabismus. These widely known conditions specifically affect the eyes development of muscle and nerve features. Being diagnosed with these conditions requires the child should undertake routine ophthalmic examinations. 

Over Accommodation
It is documented; a majority of children aged 3-4 years old tend to develop an inward eye turn perform this action because they are now capable of focusing at objects up close. This type of strabismus is strongly associated long-sighted children, especially at this age because they require more focus for close activities than a normal eye would, as a result this additional focusing causes the eye to turn in. This type of strabismus is easily treated with a suitable and fitting pair of prescription glasses from the ophthalmologist. 

Poor Binocular Control
There is a visual centre in our brain that guides our eyes to observe objects together. This provides detailed, sharp and single vision but for some children, this requires more effort and may encourage the brain to shut off an eye and causing it to drift out. Strabismus, such as these, can be improved with patching, eye exercises and glasses to facilitate the relationship between the eyes and the brain to see well together and reduce the rate of the eye drifting out.

It is important to note that if there is any amblyopia present in combination with the strabismus in any child that the amblyopia is treated first and foremost. Sole treatment of amblyopia can facilitate realigning the eyes. Once the amblyopia is managed, then treatment of strabismus can commence, this typically involves an assortment of treatments including; eye exercises, glasses and eye muscle surgery.

Strabismus Surgery
The aim of this type of surgery is to correct a child’s squint by operating on the eye muscles to straighten the eyes. This is achieved by either shortening the muscle or changing the position of the muscle to make it stronger. Unfortunately, strabismus surgery cannot correct all strabismus types. It is often noted a high chance that a second procedure will be required some stage in the future.
Benefits of Strabismus Surgery
Better appearance
Lower occurrence of double vision
Improved depth perception
Better binocular control

Tear Duct Obstruction & Watery Eye
Tear ducts are structures located inside the upper and lower corner of the eye. These ducts drain tears from the eyes down to the back of the nose. All new born babies are born with tiny ducts but some babies’ ducts are not yet completely open. A commonly reported symptom is constant watering of the eye, where tears run down the babies’ cheek. Babies with this condition are more prone to contracting conjunctivitis where antibiotic eye drops/syrups will be use to eliminate the infection. Luckily, 9 out of 10 babies with an obstructed tear duct tend to naturally open before their 1 year old.

Firstly, a non-invasive approach is preferred for treatment including; tear duct massage with warm compresses to help open up the obstructed tear duct and as required, your eye doctor will prescribe antibiotics for any associated conjunctivitis. If the previously mentioned treatments are unsuccessful, a final option would be surgery to manually open the tear duct. Currently, there is little evidence documenting the long term effects of general anaesthetic on paediatrics but all surgery carries risks and these will be thoroughly explained by your child’s eye surgeon and will answer any of your questions and considerations before undergoing surgery.