Amblyopia: what lazy eye syndrome consists of

By Cristiano Antonino On Feb 4, 2023

Amblyopia, also known as ‘lazy eye syndrome’, is a visual disorder that is very common in early childhood

It refers to a more or less marked reduction in the ability to see in one eye (unilateral amblyopia) or both eyes (bilateral amblyopia).

Specifically, the ability of one eye to correctly pick up light stimulus and send it back to the brain for interpretation is impaired.

Although the eyes appear structurally normal, the visual capacity is not fully developed and the brain preferentially uses information from the healthier, dominant eye, gradually reducing the use of the serving eye.

In numbers, amblyopia is diagnosed when the quality of vision is less than or equal to 7-8 tenths or when the weaker eye has 2-3 tenths less than the dominant one.

Today, amblyopia affects around 3-4% of the world’s population, 5% of whom are children

It is the leading cause of visual impairment in children.

Although its prognosis is almost entirely positive, it is essential not to neglect it and to intervene from an early age with regular eye examinations.

If left untreated, the disease can have more serious effects as the affected eye will no longer have normal visual capacity in youth and adulthood.

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How does sight work?

The eye is our visual organ.

The visual process is made up of small steps: even if only one of them is missing, vision is impaired.

In general, all light stimuli coming from outside are collected by the retina and sent to the brain, which processes them within a few nanoseconds.

Without this process, the eye would not be able to absorb and see images and their three dimensions.

The channels that connect the eyes and brain are called optical pathways and have a fundamental function.

On a brain level, the two eyes, although able to pick up stimuli in the same way, are not seen as identical.

There is always a dominant eye, and one that acts as a support to the principal one and ensures successful vision in three dimensions.

It may happen that the optic pathways are the victim of some pathology or lesion, or that there is an incorrect refractive defect. In both cases, the result will then be amblyopia.

With a lazy eye, in fact, the image will arrive deficient to the optic pathways and therefore the nervous system will preferentially use the healthier eye, condemning the weaker one to low vision, even in the absence of obvious structural damage.

Both eyes remain capable of each picking up its external stimulus and providing its image, but these are so different that the brain only keeps one.

In this way, the eye that is considered weaker progressively atrophies its visual capacity until it almost loses it.

It is important to intervene on amblyopia by the age of 7, the age indicated for full ocular development.

By this age the defect can be corrected with growth.

As adults, the condition persists and double vision or blindness is risked.

Types of amblyopia

Depending on its location, amblyopia can be unilateral if the deficit affects only one eye, bilateral if it affects both.

Bilateral amblyopia is very rare.

A further classification is made according to the extent of the lesion and the ocular area affected.

Functional amblyopia sees externally intact and healthy eye structures with abnormalities residing in the optic pathways.

The brain does not allow the eye to grasp three-dimensionality and slowly a visual deficit is generated.

Functional amblyopia is a consequence of other eye diseases such as strabismus, anisometropia and all refractive defects such as myopia, hypermetropia and astigmatism, where the separation between the dominant and weak eye is already clear.

Finally, amblyopia is said to be organic if eye defects and alterations are physically present, e.g. congenital cataracts, corneal opacities, retinal dystrophies and haemorrhages (real alterations to the retina and optic nerve).

Amblyopia is a condition that is difficult to detect with the naked eye

It mainly affects children who, in most cases, are unable to feel the discomfort or notice that something is wrong but do not see it as a problem.

It is precisely in order to remove any doubts that doctors always recommend regular eye examinations for the little one from the age of one.

A non-exhaustive list of the main symptoms of amblyopia includes:

Vision problems. With older children, amblyopia is less of an issue because they may complain of vision problems, especially in school with reading and writing.
Blurred vision. Usually the main symptom of amblyopia is blurred vision in one or both eyes. The child squints or covers his eyes because he cannot see well.
Inability to suddenly grasp stimuli and reflexes such as movements and depth of things.
Frequent eye fatigue, general tiredness and headaches.

In older individuals, vision may be double.

Amblyopia is usually congenital or a consequence of the presence of other eye diseases.

One of its main causes is strabismus.

An incorrect alignment of the eye muscles, hence of the eyes, already predisposes the brain to the detection of a dominant and a weak eye.

Congenital and childhood cataracts are another main reason.

Opacity of the crystalline lens creates deficits in the retina and cornea.

The light stimulus enters the eye in a distorted manner and the image on the retina is not sharp.

Refractive defects such as nearsightedness, farsightedness and astigmatism or the disorder of drooping eyelid (ptosis) can increase the possibility of developing lazy eye.

As with strabismus, the eyes already see differently and the brain identifies a healthy, dominant one and a weak one by itself.

Finally, amblyopia can be a consequence of serious eye diseases such as a corneal ulcer or glaucoma.

Rare but still present are cases in which it is triggered by retino-corode tumour pathologies, such as retinoblastoma and choroid haemangioma, a benign vascular tumour that generally affects this anatomical area.

The diagnosis of amblyopia is based on the result of the eye examination

Doctors also recommend check-ups in the first few days of a newborn child’s life if there are any noticeable changes, such as an altered reflex within the pupil, to rule out the presence of congenital pathologies that need to be treated.

In general, check-ups must be periodic, in the absence of evident alterations, the first one is scheduled around the age of 3 and then more or less every two years, also because the child is not always able to perceive and interpret the discomfort, with the risk of underestimating the problem and only catching it when it is already in an advanced stage and more difficult to treat.

During the specialist examination, the ophthalmologist (specialised in the diagnosis and treatment of eye diseases) will take care of drawing up a careful anamnesis based on the collection of symptoms and the clinical history of the little patient.

He will then carry out an objective test to search for any visual deficits and prescribe the most suitable therapy and visual rehabilitation plan in the case of amblyopia.

In visual rehabilitation, the figure of the orthoptist is fundamental, a professional figure who implements and verifies the patient’s progress in the therapy programme by proposing customised exercises according to the severity of the disorder, the patient’s age and needs.

Through orthoptic assessment, eye alignment, colour perception, ocular motility and contrast sensitivity can be determined.

Lazy eye must be diagnosed and treated as early as possible because it can still resolve properly during growth.

After the age of 7, when the visual organ is fully developed, the prognosis is hardly as good as in earlier years.

Treatment and prevention

The best treatments for amblyopia are those carried out in childhood, when the child’s eyes are still developing and therefore easier to correct.

Starting treatment early means preventing damage from worsening.

The most common treatment for amblyopia involves patching, i.e. a patch that is literally stuck on the eye that is considered dominant or less effective on the lens of the glasses.

Penalising the stronger eye means stimulating the vision of the weaker one, so as to bring them back into parity.

The treatment time varies depending on the severity of the amblyopia and how cooperative the child is.

It is usually recommended that the blindfold be applied between 3 – 6 hours daily for a period of several months.

Performing daily activities with the eye bandaged affects the speed of healing.

Unfortunately, this technique does not work in adulthood, where vision is already fully developed.

The effect of the patch can be replicated by the administration of atropine-based eye drops.

This is a special eye drops with an active ingredient that is inserted directly into the dominant eye with the result of temporarily blurring its vision, thus stimulating that of the weaker eye.

It can have some side effects such as irritation, reddening of the eyes and headaches, but these are very rare

When amblyopia is a direct consequence of the presence of other conditions such as strabismus, cataracts and refractive defects, treatment is based on the direct elimination of the cause.

While cataracts always require surgery to restore the crystalline lens, strabismus can be alleviated through the use of neuro-stimulation exercises and in severe cases by resorting to surgery.

For refractive defects, glasses or contact lenses are made to be worn.

The recommendation remains that of careful prevention with constant screening visits.

This is because, once visual loss consolidates, it remains for life without being able to resolve itself.

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