Amblyopia (Lazy Eye)

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Overview

The normal eyesight develops at the same time with the regular, equal use of both eyes. Amblyopia, also called “lazy eye”, usually begins when one eye is not used enough in order for the visual system of the brain to develop properly. The brain ignores (neutralizes) the images of the strabic eye and uses only those formed in the healthy eye, causing a poor eyesight. Amblyopia usually affects only one eye, but it can also occur in both eyes. Children can develop amblyopia since their birth until the age of 7 years.
A child with amblyopia may not realize that he is using only one eye. Ignoring the image of the affected eye is an unconscious reaction over which the child has no control.

 

Causes

Any condition which alienates the child’s eyes from forming a clear, focused image or disturbs the normal use of one or both eyes, may cause amblyopia.
In most cases amblyopia can occur in the eyes that look at two different points in space simultaneously, projecting two different images in the brain. This condition is called strabismus. In young children with strabismus the brain learns to avoid the confusion of two images, neutralizing (ignoring) the image received from one eye. Amblyopia can occur also if the child is nearsighted or farsighted in one eye than in the other. If the eyesight of an eye is clearer than the other, the brain learns to ignore the blurry image formed by the ill eye. The conditions that prevent light from entering the eye for a long time, can cause amblyopia. A damage of the lens (as cataract) or of the transparent front layer of the eyeball (cornea) may cause amblyopia. Amblyopia caused by these diseases is rare, but serious. Without early treatment of the affected eye it is possible that the normal eyesight will not be restored again.

Symptoms

Some children with amblyopia may have a deviated eye or an eye that does not move at the same time with the other eye. This is sometimes called “lazy eye”. In most children, amblyopia is hard to be found.
The signs that may indicate amblyopia or a condition that increases the risk for amblyopia are:
- Eyes do not move simultaneously in the same direction
- Eyes do not fix the same point
- Crying or pain when one eye is covered
- Lifting and lowering movements or lateral movements in order to look at something
- An opaque lesion in the cornea (the transparent layer in front of the eye such as cataracts)
- A lid that falls and covers almost the entire eye (ptosis).
Parents may not notice if their child has eyesight problems. Worrying signs may often not appear and children may not complain about eyesight problems. An eye examination is recommended for children before the beginning of school.

Investigation

A doctor may diagnose amblyopia after detecting a reduced visual acuity in one eye, during an examination and after the exclusion of other causes of low vision. Tests that discover non-convergent eyes (strabismus), the difference in diopters between the eyes or any other condition that causes amblyopia, may help in giving the diagnosis. Before the doctor should examine the child’s eyes, an anamnesis is required, which includes questions about:
- The child’s symptoms
- The family history of eyesight problems (many people in the family who have an impaired eyesight)
- Other possible risk factors such as low birth weight or premature birth
- If teachers have noticed that the child has problems in seeing the board or has difficulties in reading.

The doctor first checks the child’s eyes to see whether they both look in the same direction at the same time. A child with amblyopia may have an eye that deviates or lags behind the other eye’s movement. In the case of children aged 2 years and over 2 years, the doctor asks the child to identify or fix pictures or letters on the wall or from a collection of diagrams. The tests estimate how well the child sees the outlines and details near and far. Thus, it can be demonstrated that the child has dioptric difference between the eyes (anisometropia). Other tests, including eye pupil dilation, can be used to determine if it is necessary to use lenses to correct the eyesight and check the structure and functioning of the eye. Your doctor can perform various tests to detect cataracts and strabismus, both conditions increasing the risk for amblyopia.
The screening for eyesight problems can be made by the family doctor, pediatrician, nurse. If any disease is detected, the child will be guided towards an ophthalmologist or optometrist for a complete examination of the visual acuity.
Doctors may have difficulty in making an eyesight screening in some small children. In these cases, a method called photoscreening can be used. Photoscreening uses a special camera or a video system to get the pictures formed and reflected in the eye, requiring a minimal cooperation with the child. Although photoscreeningul does not replace an usual investigation of the eyesight, it can obtain information about the diseases that threaten the eyesight.

Diagnosis

Screening is recommended in order to detect amblyopia, strabismus and impaired visual acuity in children below 5 years. However, an expectant attitude must not be adopted, if there are possible signs of amblyopia in younger children. No child is too small to be examined by an ophthalmologist and the examination can be performed whenever there is doubt about the child’s eye health.
The American Society of Ophthalmology recommends that all children should be examined since the age of 6 months by a pediatrician, family doctor or ophthalmologist. Newborns and children should be investigated for eye diseases like cataracts, which prevent light from entering the eye and causes amblyopia. Amblyopia, because of these causes, is rare but serious. Without early treatment, the child may not develop a normal eyesight in the affected eye.

Treatment – Overview

The treatment of amblyopia is established as soon as possible after the diagnosis. The early treatment usually can compensate for the condition and should be started before the baby’s eyesight is fully developed (before the age of 9 or 10 years). The smaller the child is, the better his chances for developing a normal eyesight, when treatment is administered. Amblyopia is difficult to correct after the age of 9 years. However, recent studies argue that treatment in this age can still correct amblyopia.
Amblyopia is usually treated by an ophthalmologist. In order to be successful, the treatment must be for both amblyopia and root causes. The optical correction or contact lenses improve some conditions, as dioptric difference (anisometropia). Other diseases, like cataracts and some forms of strabismus, requiring surgical intervention. A baby born with cataracts or other conditions that prevent light from entering the eye, urgently needs treatment because amblyopia may become permanent in a few months. Amblyopia, which is the results of the misalignment of the eyes (strabismus) or unequal vision (anisometropia), develops more slowly.
The treatment corrects amblyopia, training the brain to use the signals from the eye with poor vision, building a stronger connection between the brain and the affected eye and allowing eyesight to develop normally in that eye. There are several ways to force the strabic eye to become stronger. These methods include wearing an eye patch or dark lenses (occlusion) and using eye drops or eyeglasses (relaxation).

Occlusion
When covering the stronger eye, the brain is forced to use and develop a better view in the weak eye.
Wearing the eye patch.
Covering the healthy eye with an adhesive eye-patch or a dark patch made of an elastic band is the most common method of treatment. If the child wears glasses, the doctor may put a patch on one lens. The child must wear the patch all the time or only during the day for several weeks or months. Severe cases may take a longer period of time. A recent study shows that wearing a patch during activities that require the close eyesight, for 2 hours per day, is similar to wearing a patch 6 hours a day.
Wearing opaque contact lenses.
Amblyopia can also be treated by placing a dark contact lens in the normal eye. This can be useful when your toddler refuses to wear a patch or looks over the patch or glasses. Learning to remove and reintegrate the contact lenses is necessary.

Relaxation
This treatment fades or darkens the eyesight of the dominant eye of the child, rather than prevent it completely. This causes the brain to rely on the eye with poor vision. Relaxation is less used than occlusion. It is beneficial for mild cases of amblyopia; in severe cases, it is difficult to dim and darken enough the normal eye, so that the brain prefers using the affected eye.
Ophthalmic solution (eye drops)
The most common treatment method of relaxation is represented by the use of ophthalmic solutions to blur vision in the healthy eye and force the brain to use the strabic eye.

Eyeglasses
Eyeglasses with the opaque lens in front of the healthy eye, forces the brain to use the weak eye. The doctor will prescribe certain breaks during the treatment in order to allow the child to use the healthy eye and protect it from damage or weakness.
Amblyopia may reappear after a successful treatment, so that visual examination is recommended for children up to age 9 or 10 years.
Home treatment
Treatment of amblyopia is made every day, both at home and at school. Everything possible is tried in order for the treatment to be successful. If eye drops are used, it must be observed if the child uses them as the doctor prescribed. The teacher is told about the child’s situation, so that he should support the child during treatment.
In order to be effective, the eye patch should be worn as long as it is recommended. It is important for the child to be helped to comply with the treatment so as to develop a better eyesight. The major cause of the shortcomings of amblyopia treatment is not using eye patches at the doctor’s recommendation.
If the child underwent a treatment for amblyopia, it is recommended to follow the medical advice of going to future periodic examinations. Amblyopia can recur even after a successful treatment.
The younger the child, the better the results of amblyopia treatment. If it is suspected that a child has amblyopia and other eye conditions, consulting a specialist is necessary. Amblyopia treatment should begin immediately after the disease was discovered.
Amblyopia is difficult to correct after age 9 years. However, recent studies argue that certain forms of treatment for amblyopia can improve even in older children and adults.

 

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