Amblyopia – Lazy eye
Does your child have a "lazy" eye? A crossed eye? Are they showing signs of poor vision? A white pupil? Or a drooping eyelid? They may have amblyopia, a condition affecting 4 to 6% of the population. Amblyopia is a decrease in vision in one eye, or more rarely in both eyes, even with corrective lenses. Most often, it's due to a difference in prescription between the two eyes (one eye seeing more blurry than the other), but it can also indicate an underlying eye condition that requires treatment. Generally, amblyopia is reversible when treated before the age of 6.
What is amblyopia?
Amblyopia refers to an eye that has not seen properly since birth (congenital disease) because the eye-brain connections have not developed correctly.
This abnormal development is linked to a lack of visual stimulus on the affected eye during childhood.
The absence of visual stimulus can be caused by a refractive error (most often hyperopia) or an organic abnormality (congenital cataract, ptosis, retinal disease).
In short, the eye and the eye-brain connection never become powerful enough to see, even with the best pair of glasses.
Who is affected?
Amblyopia is a childhood disease that will remain for life if it is not treated and corrected before the age of approximately 8 years.
The limit of 8 years is set because this is the age from which eye-brain connections cease to develop.
What are the causes of amblyopia?
Amblyopia results from an early alteration (in childhood) of visual experience, either by deprivation of an image (one of the two eyes does not see or sees very poorly), or by disruption of the binocular link (the two eyes perceive an image of very different quality, so that the brain cannot superimpose them).
The fact that this disturbance takes place during the maturation period of the visual system (from 0 to 10 years) will favor normal development of vision in the eye that "sees best", at the expense of the penalized eye which therefore becomes amblyopic.
The different types of amblyopia
Amblyopia can be classified into two categories:
Organic amblyopia is secondary to a pathology of the eye or visual pathways, which alters the quality of the image perceived by that eye (for example congenital cataract), or deprives it of an image (for example ptosis: upper eyelid that droops and obscures vision).
Functional amblyopia is the most common type and is not related to any eye or visual pathway disease. It is caused by a refractive error (a difference in vision between the two eyes) or strabismus, which disrupts binocular vision.
Some rarer forms of amblyopia are described as mixed because they combine both organic and functional amblyopia.
The diagnosis of amblyopia
Amblyopia is diagnosed using a visual acuity test. An eye is considered amblyopic when there is a difference in visual acuity of at least 2/10 between the two eyes.
For example, if the right eye is 9/10 and the left eye is 6/10, the left eye is amblyopic.
Visual acuity is determined after instilling cycloplegic eye drops into the child's eyes (5 to 7 days before the examination for Atropine, and 60 to 45 minutes before the examination for Skiacol), in order to obtain the most accurate correction possible.
Degrees of amblyopia
There are several levels of amblyopia:
Severe amblyopia: the visual acuity of the amblyopic eye is less than or equal to 1/10.
Moderate amblyopia: the visual acuity of the amblyopic eye is between 2/10 and 5/10.
Mild amblyopia: the visual acuity of the amblyopic eye is greater than or equal to 6/10.
Diagnosing amblyopia is not easy in children because they do not realize it, since they only have one affected eye (the non-amblyopic eye "compensates" for the amblyopic one).
Amblyopia is primarily diagnosed during a visual screening. However, certain signs are suggestive of amblyopia, such as the presence of strabismus, which is associated with it in 50 to 70% of cases.
Visual acuity cannot be measured in preverbal children (before the age of 2). Amblyopia is diagnosed through examinations that assess the child's visual behavior.
Finally, in order to determine whether the amblyopia is organic or functional, the ophthalmologist performs a fundus examination (often at the same time as the cycloplegic examination), which could reveal the presence of a congenital cataract or a retinal anomaly, for example.
Management of amblyopia
It is important to note that amblyopia is reversible if treated early, typically before the age of 6, a period during which visual experience influences the maturation of the visual system (this is known as brain plasticity).
Medical treatment takes place in several stages. In the case of organic amblyopia, the underlying eye disease must first be treated (for example , surgery for a congenital cataract ).
Full optical correction – Glasses for permanent wear
Regardless of the type of amblyopia (organic, functional or mixed), a visual examination under cycloplegic eye drops (Skiacol or Atropine) is systematic.
Prescribed glasses must be worn continuously to be effective.
Alternating occlusion – Eye patch
The standard treatment for amblyopia is occlusion of the dominant eye (non-amblyopic eye) with an adhesive patch in order to stimulate visual development of the amblyopic eye (the "lazy" eye).
The first phase is the attack treatment: during this phase, the eye is permanently closed (total closure = 24 hours a day).
The duration of the attack treatment depends on the child's age: it lasts as many weeks as the child's years of life (3 weeks for a 3-year-old child, for example).
The child is then gradually weaned off the patch, while ensuring that both eyes remain at the same vision.
Encourage your child to wear the patch
Children may not want to wear an eye patch. To help them, you need to explain how important this treatment is for their ability to see properly.
Reassure your child by telling them that many children wear an eye patch for the same reason.
You can ask him to practice putting an eye patch on a doll. Or let him decorate his eye patch with crayons or markers.
Also explain the amblyopia treatment to his teacher so they can monitor him during the day. Ask the teacher to encourage your child and watch for any inappropriate teasing.
Factors to consider when treating with an eye patch:
In very rare cases, it is possible to use the patch too intensely. This can affect the vision of the stronger eye, which in turn becomes amblyopic.
Keep your child's appointments with the ophthalmologist so that the vision in both eyes can be closely monitored.
The skin stuck to the eye patch can become irritated. To help, try a different size or brand. Also, adjust its position each day.
At first, your child may be clumsy while wearing a patch because their field of vision is narrowed. Try to keep an eye on them when they are going down stairs or playing on high play structures.
Monitoring and development
Prescribed glasses are often poorly tolerated at first by the child, due to the strong correction: there is an adaptation period, which is all the shorter if the doctor and then the parents reassure the child.
Similarly, covering up "the eye that sees" can cause some anxiety in the child (especially before the age of 2), but it remains transient.
Visual acuity is assessed for the first time after the initial attack phase. The objective of this phase is to achieve isoacuity, that is, equal visual acuity between both eyes.
Once this is achieved, maintenance treatment is put in place. This consists of a progressive reduction of occlusion time (16 hours per day, then 12 hours, then 8 hours…) over several months, or the placement of a Ryser filter (semi-opaque filter) on the corrective lens of the dominant eye.
In parallel, an examination under cycloplegic eye drops (Skiacol or Atropine) should ideally be carried out every 6 months in order to adapt the child's optical correction.
The total duration of treatment cannot be known at the outset, as it varies depending on the progress of each patient.
Prognosis
When amblyopia is treated early, the prognosis is most often excellent!
The earlier amblyopia is diagnosed, the better the vision will be.
Similarly, the more diligent the parents and child are in rehabilitation, the better the visual outcome will be.
Conclusion
Amblyopia is a common condition in pediatric ophthalmology. The earlier it is detected and treated, the better the visual prognosis.
Its treatment is simple and effective if followed correctly. It consists of occlusion of the non-amblyopic eye, initially total and then progressively reduced.
The difficulty of this issue lies in the fact that it can go unnoticed (the child does not complain), while hiding an eye disease (cataract): for these reasons, an ophthalmological screening must be essential for all children under 6 years of age.
Frequently Asked Questions
How does an amblyopic eye see?
It all depends on the degree of amblyopia! It is possible to simulate amblyopia with a pair of glasses:
– Mild amblyopia – Vision at 7-8/10 – Vision after putting fingers on the lenses.
– Moderate amblyopia – Vision at 5-6/10 – Vision after putting glasses under water.
– Severe ablopia – Vision at 3-4/10 – Vision after fogging up glasses.
Up to what age can amblyophia be treated?
Amblyopia can be effectively treated up to the age of 6 or 7. From age 8 onwards, results are often partial, and very disappointing after age 9 or 10. However, trying a few weeks of treatment can lead to some improvement in vision.
How long does amblyopia treatment take?
The duration of treatment varies. Generally, equal visual acuity (the ability to see 20/20 in both eyes) is achieved after 2 to 4 months. Maintenance treatment with alternating patches is then necessary for a period approximately equivalent to achieving equal visual acuity.
Whatever happens, regular monitoring (annually or biannually) is necessary until the age of 10.
Can a lazy eye in an adult be treated?
Unfortunately not. Adults do not possess the brain plasticity necessary to develop eye-brain connections. After the age of 10, any vision not yet acquired cannot be recovered.