The brain and eyes work together to produce vision.
The eye focuses light on the back of the eye known as the retina.
Cells in the retina then activate nerve signals that travel along the optic nerves to the brain .
Amblyopathy called amblyopia, is a medical term that describes a decrease in visual acuity or vision in one or both eyes, which occurs because the brain cells responsible for the vision of the affected organ do not develop due to failure in stimulation.
The eye looks intact, but is not being used normally because the brain is favoring the other eye. This condition also known as lazy eye or lazy eye is the most common cause of visual impairment during childhood.
What Causes Amblyopia?
Amblyopia can be due to any condition that prevents the eye from focusing clearly. Amblyopia can be caused by misalignment of the two eyes, a condition called strabismus .
With strabismus, the eyes can enter (esotropia) or turn (exotropia). Occasionally, amblyopia is caused by a clouding of the front of the eye, a condition called cataract.
A common cause of amblyopia is the inability of one eye to focus, as well as the other. Amblyopia can occur when an eye is more myopic, more foresighted, or has more astigmatism . These terms refer to the eye’s ability to focus light on the retina.
Farsightedness occurs when the distance from the front to the back of the eye is too short. Future-sighted eyes tend to focus better at a distance, but have more difficulty focusing on close objects.
Nearsightedness, or myopia, occurs when the eye is too long from front to back. Nearsighted eyes tend to focus better on nearby objects. Eyes with astigmatism have difficulty focusing on far and near objects due to their irregular shape.
Although there are many types of amblyopathy, their basic mechanisms are believed to be the same, although each factor may contribute different amounts for each specific type of amblyopia.
In general, amblyopathy is believed to be the result of disuse of inadequate foveal or peripheral retinal stimulation and / or abnormal binocular interaction causing different visual input from the foveas.
Three critical periods in the development of human visual acuity have been determined. During these time periods, vision can be affected by the various mechanisms to cause or reverse amblyopathy.
These periods are as follows:
The development of visual acuity from the range 20/200 to 20/20, which occurs from birth to 3-5 years.
The period of greatest risk of deprivation amblyopia, from a few months to 7 or 8 years.
Period during which recovery from amblyopia can be obtained, from the moment of deprivation until adolescence or sometimes even adulthood.
It is unknown whether different visual functions (eg, contrast sensitivity, stereopsis) have different critical periods. In the future, determining these time frames can help modify the treatment of amblyopia.
Signs and symptoms of amblyopathy
Symptoms typically include:
- Squinting or closing one eye.
- Impaired depth perception.
- Poor hand-eye coordination.
- Stumbling and / or accident prone.
- Problems with the movement of the micro eyes.
- Slower reading and comprehension speed.
Another clue that your child may have amblyopia is if he or she cries or complains when covering one eye.
You can try this simple home screening test by simply covering and uncovering your child’s eyes (one eye at a time) when they are doing a visual task, such as watching television.
If your child does not mind having one eye covered, but opposes it when they do, this may suggest that the covered eye is the “good” eye and that the uncovered eye has amblyopia and causes blurred vision.
But a simple screening test is not a substitute for a comprehensive eye exam.
Have your child’s eyes examined as recommended to make sure they have normal vision in both eyes and that the eyes work together as a team.
Diagnosis of amblyopathy
Imaging studies that may be helpful when the eye exam is normal and there is a suspicion of an organic cause include the following:
- Magnetic resonance.
- Fluorescein angiography (to evaluate the retina).
Other tests that may be helpful in diagnosis include the following:
- Electrophysiological studies.
Treatment and management of amblyopathy
Treatment tends to be more effective the younger the child is.
After the child is 8 years old, the chance of improving vision decreases significantly, but it can still be effective.
There are two approaches to treating lazy eye:
- Treat an underlying eye problem.
- Make the affected eye work so that vision develops.
Treatment for underlying eye problems
Many children who have uneven vision, or anisometropia, do not know they have an eye problem because the stronger eye and brain make up for the deficit. The weaker eye progressively worsens and amblyopia develops.
Glasses: Children with short vision, farsightedness, or astigmatism will be prescribed glasses. The child will have to wear them all the time so that the specialist can monitor their effectiveness in improving vision problems in the lazy eye.
Glasses can also correct an eye roll. Sometimes glasses can resolve amblyopia and no further treatment is required.
It is not uncommon for children to complain that their vision is better when they are not wearing glasses. They should be encouraged to use them for the treatment to be effective.
Cataract surgery, or phacoemulsification : If a cataract is the cause of amblyopia, it can be surgically removed under local or general anesthesia.
Droopy Eyelid Correction: For some people, amblyopia is caused by an eyelid blocking the vision of the weaker eye. In this case, the usual treatment is surgery to lift the eyelid.
Get the lazy eye to work
Once vision is corrected and underlying medical problems are resolved, other steps can be taken to help improve vision.
Occlusion or use of a patch: A patch is placed over the “good” eye so that the lazy eye has to function. Since the brain only receives information from that eye, it will not ignore it. A patch will not get rid of an eye twist, but it will improve vision in the lazy eye.
The length of treatment depends on many factors, including the age of the child, the severity of their problem, and the extent to which they adhere to the specialist’s instructions. The patch is usually worn for a few hours each day.
A child should be encouraged to do close-up activities while wearing the patch, such as reading, coloring, or doing homework.
Atropine Eye Drops: May be used to blur the vision of the unaffected eye. Atropine dilates the pupil, which produces a blurry image when you look at things closely. This makes the lazy eye work more.
Atropine is usually less conspicuous and uncomfortable for the child, compared to a patch, and it can be just as effective. Children who cannot tolerate the use of a patch may be prescribed eye drops.
Vision exercises: This involves different exercises and games aimed at improving the development of vision in the affected eye of the child. Experts say this is helpful for older children. Vision exercises can be done in combination with other treatments.
Surgery: Sometimes eye surgery is done to improve the appearance of an eye twist, resulting in better eye alignment. This may or may not improve vision.
After 1 year, approximately 73% of patients show success after their first trial of occlusion therapy.
Studies have shown that the number of patients who retain their visual acuity level decreases over time to 53% after 3 years.
Risk factors for failure to treat amblyopathy include the following:
- Type of amblyopia: patients with high anisometropia and patients with organic pathology have the worst prognosis. Patients with strabismic amblyopia have the best outcome.
- Age at which therapy began: Younger patients seem to improve.
- Depth of amblyopia at the start of therapy : the better the initial visual acuity in the amblyopic eye, the better the prognosis.
Complications associated with amblyopathy
Blindness: If left untreated, the patient may lose sight in the affected eye. This vision loss is usually permanent.
Turn of the eye: Strabismus, where the eyes are not properly aligned, can become permanent.
Central vision: If amblyopia is not treated during childhood, the patient’s central vision may not develop properly. The problem can affect your ability to perform certain tasks.
Parents should be educated about the importance of treatment and compliance, as well as the visual implications, because the treatment of amblyopia is often in the hands of the parents.