Poor vision or amblyopia

Amblyopia (also called poor vision or impaired vision) means that the vision of an eye does not fully develop in childhood.

Although visual impairment usually affects only one eye, it can also occur bilaterally.
Amblyopia is the most common cause of weak eyesight in children.

If someone has poor vision, it does not always have to have a recognizable abnormality of the eye.

Amblyopia develops when the nerve pathways between the brain and eyes are not stimulated appropriately.
As a result, the brain favors one eye, as the vision of the other eye is reduced.
Over time, the brain can ignore the signals received from the weaker eye.


What are the causes of amblyopia?

Strabismus amblyopiaStrabismus is the most common cause of amblyopia. To avoid double vision through the unevenly aligned eyes, the brain ignores the visual input of the misaligned eye and creates amblyopia in this eye (“weak-sighted eye”).

Refractive or anisometric amblyopia. Sometimes amblyopia is caused by refractive errors of the eyes, even if the alignment is perfect.

Amblyopia is caused by the following:

  1. myopia,
  2. Astigmatism
  3. Farsightedness

These refractive errors cause a blurred image, the blurred images are transmitted to the brain.
Over time, the brain begins to ignore or suppress the less clear images, resulting in amblyopia in one or both eyes.

In these cases, the brain relies on the eye, which has a lower refractive error and excludes the blurred vision of the other eye by causing amblyopia in this eye by not using it.

Deprivation amblyopia (or compression amblyopia). Here, the weak eyesight of the eye is caused by something that hinders light entry into the child’s eye, for example, a congenital cataract.
Rapid treatment of congenital cataracts is essential for normal visual development.

Ptosis. This is a drooping eyelid. Therefore, if the light cannot penetrate the eye, the eye is not used. This can lead to amblyopia.

Toxic (or dietary) amblyopia. A type of organic amblyopia in which the lack of nutrients or certain toxic substances can cause amblyopia.
Alcohol, tobacco, or a vitamin B deficiency can lead to toxic amblyopia.

Heredity. Genetics also play a role.
Amblyopia is an inherited disease.
It is more common in premature babies or children suffering from developmental disorders.

Symptoms of weak vision

If treatment for amblyopia is not initiated as early as possible, various problems can develop that can seriously affect vision:

  1. The defective eye can develop a serious and permanent visual defect.
  2. Depth perception (seeing in three dimensions) can be lost because both eyes have to see well.

Examination and diagnosis of visual impairment

The doctor diagnoses a weak-sighted eye during a thorough eye examination. The doctor states:

  • whether one eye is squinting;
  • there is a difference between the vision of both eyes;
  • there is a visual impairment of both eyes.

Depending on the age of the child, the following tests are performed:

  • Newborns. The red reflex test, which uses an illuminated magnifying device (ophthalmoscope) to look for a cataract, pupillary and corneal reflexes, eye movements.
  • Infants. Test of the ability to fix the gaze and follow a moving object (examination of eye movements).

Control of strabismus 

  • Infants. Red reflex test and examination of spatial vision (stereopsis): Long stereo test.
  • Preschoolers and older children. Perform tests using images or letters to determine if there are any refractive defects. One eye is covered for examination of the other.

What is the therapy for amblyopia?

  1. Correction of eye defects (such as strabismus) or refractive errors (for example, nearsightedness or farsightedness). Refractive anomalies such as nearsightedness or farsightedness can be corrected by glasses.
    A cataract can be treated surgically.
  2. Rehabilitative treatment: exercises for the weak-sighted eye to improve function, so that vision can develop correctly.

Early treatment is important.

When is it too late to treat weak eyesight?
A recent study by the National Institutes of Health (NIH) has confirmed that therapy can also improve vision as an adolescent (around 14 years old).

Penalization or eye patches

In order to achieve better results in amblyopia treatment, it is recommended to exclude the better seeing eye from seeing (occlusion).
For this reason, the eye patch attached to the skin is an effective therapy.
Eye patches and bandages attached to the glasses are less effective and are rarely recommended.

If the child does not tolerate the eye patch treatment, atropine eye drops may be useful under certain circumstances.
The eye drops can be used if the child refuses the eye patch.
Atropine is dripped into the dominant eye and leads to temporary blurred vision, forcing the child to use the visually impaired eye.

From an aesthetic point of view, eye drops are less noticeable than an eye bandage.

Side effects of atropine include:

The pediatric ophthalmologist prescribes the appropriate number of hours in which the eye bandage should be worn daily.
During treatment with an eye bandage or atropine eye drops, it is important that the child is cared for by the ophthalmologist to prevent the development of amblyopia of the bandaged eye.
After the age of eight or nine, the effect of treatment with a bandage or atropine eye drops is greatly reduced.

Glasses and contact lenses for weak eyesight

Another therapeutic option is glasses that prevent seeing clearly with the healthy eye.
Usually, a lens is made opaque so that the child cannot see with it.
Rarely, special contact lenses are used to prevent good vision.
Contact lenses can be difficult to use in young children and extreme
care is needed when cleaning the lenses to avoid eye infections.

Do eye drops work for all visually impaired children?
Not all children have advantages in therapy with eye drops.
Atropine eye drops do not work well if the stronger eye is nearsighted.

How many hours a day does the bandage have to be worn?
The mainstay of the treatment of amblyopia is covering the dominant eye for the whole or half day during the waking state.
Recent studies suggest that you should not wear the bandage as long as possible, but that shorter periods of time bring similar results in a not severely impaired eye.

How long does it take for the success of the therapy to become apparent?
Although vision improvement usually occurs within a few weeks of starting therapy with the bandage, optimal results take many months to achieve.
Once vision is improved, temporary wearing of the bandage or atropine eye drops can help prevent relapse.
This maintenance therapy may be recommended for a few months or years on the advice of the ophthalmologist.

What happens if a child refuses to wear the bandage?
Not infrequently, children with amblyopia refuse to wear the bandage and take it off when they are alone.
The use of the bandage should begin at a time when one can devote full attention to the child (for example, on weekends).
As a rule, the first days are the most difficult.
One should occupy the child with games or television if the bandage is worn.
If the child removes the bandage, it should be put back on as soon as possible.
Sometimes it is recommended for smaller children to put their hands in the stocking so that they cannot remove the bandage.

Exercises against weak eyesight

Adults and children can correct amblyopia by performing exercises, using lenses or having a laser procedure.

There are software programs like RevitalVision® that bring excellent and lasting results:

  1. Improvement of at least 2/10
  2. Optimization of contrast vision to 100%

This program was approved by the FDA (Food and Drug Administration) in 2001:

Vision depends on the input received from the eye and the processing by the brain cells. The theory of these eye training programs is based on:

  • visual stimulation,
  • Improving the neural connections and interactions in the brain responsible for vision.

The software creates individual exercises based on so-called Gabor patches and:

  • improve contrast vision,
  • ensure a clear visual acuity.

The software modifies the exercises based on the results obtained in the previous session.
The exercises are carried out on a PC connected to the Internet, so they can be done from home.

The practice session lasts about 30 minutes.
It is advisable to carry out this therapy at the same time every day, such as after lunch or dinner, in this way the patient does not miss an exercise session.

Does Tetris correct poor vision in adults?
If a child has weak vision, the normal treatment is the bandage on one eye.
Adults usually do not respond to this type of therapy.
In the case of impaired vision in adults, there is special software (computer program) that can stimulate neuronal changes that improve vision.
Recently, scientists have tested the video game Tetris as a pleasurable tool for this type of therapy.
The game scene changes quickly, forcing both eyes to work together.
This eye exercise expands the plasticity level of the visual cortex, the area in the brain that processes visual input.
In a study of Tetris, 18 adults performed the test over two weeks, half of whom wore glasses covering one eye.
In the group that played with two uncovered eyes, a significant improvement in vision was found.
A report on the study appeared in the April 2013 issue of Current Biology. — L.S.

Method according to Bates
The method according to Bates is an exercise program for the eyes, which was developed by Doctor William Bates in
the 20-ies.
The exercises are designed to treat the majority of eye disorders, including amblyopia, by improving the functioning of the eye muscles while relaxing them.
The Bates method aims to train the eye muscles so that the eyes
can align themselves.
Some new techniques are based on the application of the Gabor filter and visual neurostimulation.

Surgery for amblyopia

Eye lasers
After a surgically performed PRKLASEK or LASIK, the patient has the same vision as contact lenses.
If the impaired eyesight is caused by a refractive error, the laser can also correct this disorder in adults, as vision is improved.
In case of refractive errors, laser surgery is contraindicated if the patient is still a minor; consequently, this therapy must not be used in children either.

The operation of the eye muscles is a treatment for strabismus, misaligned eyes can be corrected.
On its own, however, surgery does not completely solve the problems of weak vision.
The operation makes it possible to direct the eyes straight ahead and allows a coordinated function.
In strabismus children with amblyopia, the visual impairment must be treated before strabismus surgery.
Children born with a cataract may need surgery to remove the cataract.
After the operation, the children need vision correction using glasses or contact lenses and must wear an eye bandage.

Expectations or prognosis for patients with amblyopia

Children who were treated before the age of 5 recover almost completely, although there may still be problems with depth perception.
If treatment is delayed, it can lead to permanent vision problems.
After 10 years, only partial restoration of vision can be expected.

Consequences of amblyopia

  1. In case of muscle problems of the eye, various surgeries can help, which can bring some complications.
  2. Permanent loss of vision in the diseased eye and consequently a loss of binocular perception of space: one cannot perceive the depth and distance of the objects.

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