Amblyopia is a childhood condition (also referred to as ‘lazy eye’) where one eye (or less frequently both eyes) fails to work in harmony with the brain, leading to decreased vision. It affects approximately 2% of children. As they may not notice an issue with their vision, it is important for parents to be aware of any indications a child’s vision may be impaired and to ensure they receive regular eye tests.
With Amblyopia, a child can develop a greater reliance on the better-functioning eye and neglect the eye which has not formed as strong a connection with the brain. As a child’s vision develops from birth through to seven or eight years of age, it is important to seek treatment to correct the condition as early as possible and before a child’s vision has fully developed.
Amblyopia causes poorer quality vision by the nature of the weaker connection made between the affected eye(s) and the brain (often as a result of blurred or double vision). Depending on the severity of the underlying problem, some indiviudals may experience a partial loss of vision, whereas other individuals may only be able to recognise motion. The eye which is not affected by the condition often attempts to make up for the difficulties leading to a greater reliance on this eye, leaving the other eye to become ‘lazy’. As the child may not notice that there is a problem with their vision, it is important for parents to be aware of any behaviour which may signal an issue. This may include:
• Squinting or closing one eye while reading or watching television
• Having a crossed or turned eye (known as strabismus)
• Turning or tilting the head when looking at an object
• Having problems reading, writing or drawing
Individuals living with amblyopia lack binocular vision, or stereopsis – the ability to blend the images of both eyes together. Stereopsis is what allows us to appreciate depth. Without it, the ability to judge distance is impaired.
There can be a number of reasons why Amblyopia develops.
A condition known as Strabismus most commonly gives rise to Amblyopia. Strabismus is defined by a squint in one eye, with both eyes commonly observed as looking in different directions. In such cases, the brain will ignore the signals from the affected eye and only use the information from the “good eye”. Strabismus may be inherited, arise after short or long-sightedness develops or after a virus or injury.
Amblyopia may also be caused by a refractive error (or poor focusing of light into the eye) as a result of short-sightedness (myopia), long-sightedness (hypermetropia) or astigmatism (uneven focus in the eye). It develops where a difference occurs in the degree of short-sightedness, long-sightedness or astigmatism between eyes. This difference causes the brain to ignore the eye with the most significant refractive error, giving rise to amblyopia. This is known as Anisometropic Amblyopia.
If a child has significant refractive errors (poor focusing of light into the eye), on account of long-sightedness (hypermetropia) or astigmatism (uneven focus in the eye) which might not have been detected, this can cause Ametropic Amblyopia. In such cases, the child has poor vision in both eyes.
Another cause of Amblyopia can be as a result of one or both eyes being prevented from seeing, known as Stimulus Deprivation Amblyopia. It is often regarded as the most severe forms of Amblyopia and can be caused by a scar or eye disease, a congenital cataract, a drooping eyelid (from ptosis or blepharoptosis) or glaucoma. Surgery or injury to the eye may also cause this form of Amblyopia.
Amblyopia is diagnosed through a number of tests which are important for providing the correct diagnosis. Importantly, young children should have a routine eye exam performed by the age of two to three to check for any potential problems associated with their vision. It is important that Amblyopia is identified as early as possible- ideally before 6 years of age where treatment can be most beneficial.
The eye doctor will ask about an individual’s medical history, including any family history of eye conditions. Individuals will receive an eye examination where they may be asked to read letters off a chart (Snellen chart). If possible, they may check intraocular pressure and examine visual field and visual acuity. The degree of refractive error (i.e. myopia, hypermetropia or astigmatism) will be measured. Tests for colour vision may also be performed.
When amblyopia is suspected, the eye doctor will evaluate the following: eye alignment, eye movements, and fusion (the brain’s ability to blend two images into a single image).
There are treatments available for Amblyopia. It is important to note that early detection and treatment (before 6 years of age) will yield the best chances of improvement – before the child’s brain learns to permanently suppress or ignore the weaker eye.
There are two avenues for treatment of amblyopia. These include actions which will force the weaker eye to work such that vision can develop correctly and options to target underlying eye conditions.
The main treatment for Amblyopia is correcting refractive error by wearing prescription glasses. In addition to this, the amblyopic eye is encouraged to work by occluding the better-seeing eye for several hours per day.
The exact length of time the patch will be required each day will depend on the severity of the condition, how old the individual is and if the individual follows the recommendations closely. Generally, benefits from wearing a patch are best when an individual is less than 7 or 8 years of age.
Eye drops are another option which may be used, particularly in cases where the child isn’t able to wear a patch. These drops (known as atropine) are used to blur the vision in the good eye, prompting the weaker eye to work. The eye drops are given once a day and are typically as effective as wearing a patch. Some side effects which may accompany this treatment include irritation of the eye, a reddening of the skin around the eye, heart palpitations and headaches. However, these effects are relatively rare.
Strabismus surgery is possible in strabismic amblyopia. It is performed once glasses and occlusion treatment have been used to their maximum effect. Strabismus surgery is not a cure for glasses, and these must still be worn after surgery if present beforehand.
Problems that impair vision such as cataracts, a squint or droopy eyelids (ptosis) can often require surgery. This surgery can be carried out very readily, usually under a general anaesthetic. This may require an overnight hospital stay for monitoring purposes and the individual may be required to use eye drops or wear an eye patch for a time after surgery.
Vision therapy is an option being employed to help promote the development of a child’s vision. This type of therapy works by using games and exercises to prompt the use of a child’s weaker eye. It can often be used alongside other therapeutic options such as glasses or occlusion.
General eye check-ups are important for people with Amblyopia, as these individuals may still be at risk of developing other kinds of eye problems that affect the general population, some of which may be treatable.
No matter what level of vision a person may have, it is important to look after the eyes. To find out more about what can be done to take care of the eyes on a daily basis, please visit our Tips for Good Eye Health.
Research for amblyopia has gathered pace in recent times. With that, better diagnostic practices, improved treatment options and new vision therapies are being investigated to improve vision.
There are efforts underway to find improved ways of diagnosing amblyopia. One such study is investigating how the assessment of “crowding” may identify cases of amblyopia more readily. Crowding is known as the negative effect of surrounding features on how a target is seen by a person. Researchers are examining ways by which this can be better presented in diagnostic tests to identify amblyopia more readily.
Researchers are examining current treatment approaches with an aim to improving the quality of those treatments. Researchers are also looking to new treatment options. One such example is a drug treatment called Donepezil. This treatment has been shown to improve vision and reduce amblyopia in animal models and is now being investigated in a small clinical trial.
There are other therapeutic avenues being explored for amblyopia. One such example includes transcorneal electrical stimulation. This technique currently being examined in a clinical trial investigates whether non-invasive stimulation of the retina can provide benefit in improving visual function.
Researchers are also actively assessing new and updated vision therapies. One such vision therapy being examined is a binocular game played 5 days a week whilst wearing glasses. Researchers are examining whether this therapy is a way of effectively treating amblyopia. Vision therapies using various technologies such as tablet applications and video games are also being evaluated in clinical trials.
Further information about clinical trials can be found on their website and can be searched by condition and trial location.
Receiving a diagnosis can be overwhelming for anyone, but this is not a journey that you have to make alone. There are many groups and resources available to provide support for people living with Amblyopia.
Fighting Blindness offers a free and confidential counselling service (Insight Counselling). For further information please contact firstname.lastname@example.org or call 01 6746496.
A mindfulness group is also available on every Wednesday at the Fighting Blindness office at 11am.
For technology support and guidance, the Dublin-based Technology Exchange Club meets every Monday at the Fighting Blindness office at 11am. Another Technology Exchange Club, based in Cork, meet every Saturday in the Cork City Library, Grand Parade, Cork City at 11am. The Cork-based club do not meet on Bank Holiday weekends or on the second Saturday of the month. For further information please contact email@example.com or call 01 6746496.
Féach provides support for parents of children living with sight loss in Ireland.
ChildVision is the national education centre for children with sight loss in Ireland.
NCBI (National Council for the Blind in Ireland) provides support and services for people living with sight loss in Ireland.
Irish Guide Dogs for the blind helps individuals and their families to achieve improved mobility and independence.