Amblyopia is a disorder of the eye where the eyes and the brain do not work in proper coordination. This results in decreased vision in one eye while the other eye works perfectly. This disorder is commonly known as lazy eye. Amblyopia persists even with prescribed contact lenses and eye-glasses. The eye looks normal but does not work as it is intended to work. The condition affects more than 1 million people in India itself. Amblyopia takes onset before five years of age and in most cases, only one eye is affected. Eventually, the brain stars ignoring signals from the weaker eye.
Symptoms in the lazy eye are hard to notice during childhood. It is only when once the symptoms get worse, they become noticeable. If the defect is not treated the brain will start ignoring the images from one eye. This means that the brain tends to move the image that both the eyes see to just one side.
Being cross-eyed or having the eyes move inwards and being wall-eyed or having the eyes move outwards are also the symptoms of amblyopia. This wandering of eyes or the misalignment of eyes is also known as strabismus.
There is a difference in the level of focus in both the eyes. This means that one eye shows a blurry image, while the other shows a perfect one. Diplopia or Double vision may also occur due to amblyopia. Double vision is a problem with the eyes that causes a person to see two objects when only one is present. Constant squinting of eyes may also take place.
Causes of Amblyopia:
Amblyopia is caused when the brain uses one eye more than the other. It is related to the development of the brain. In this particular case, the nerves that control functions related to sight and vision. The most common cause of amblyopia is the inability of one eye to focus as well as the other.
There are three main types or causes for amblyopia:
Strabismus is a condition where eyes are misaligned. This results in the person being cross-eyed (strabismus) or wall-eyed (divergent strabismus). Strabismus also means the constant movement of eyes inwards or outwards. The constant movement of one eye can also result in amblyopia. People who have strabismus cannot focus both the eyes on an image at once. This leads to the person experiencing Diplopia or seeing double of an image. In adults, this problem may persist, but kids are more neuroplastic in this regard. Therefore, in kids, the brain may start ignoring the image or visual signals from one eye to eliminate the double image and thus developing amblyopia. Constant elimination of the image from one eye may result in the vision of that eye to get worse. People with strabismus have a hard time reading small texts and have a slow reading time than a person with normal eyesight.
Refractive Amblyopia is the result of an imbalance in refractive error of the two eyes. It takes place due to a difference in the power levels of both the eyes. This is known as anisometropia. The eye that provides a much clear image plays the role of the dominant eye. The resulting image in other eye is blurred which causes the unusual development of the visual system. Refractive amblyopia is easy to miss by the physicians due to its lack of physical manifestation or appearance. Refractive Amblyopia is caused by the person being Near-sighted (Myopia), meaning that the person sees closer objects clearly as compared to the further objects or Far-sighted (Hyperopia) which means that the person can see the objects far away clearer than the ones closest to them. Astigmatism in the eye at an early age can also cause amblyopia. A higher degree of astigmatism may cause eye strain, fatigue or headaches. Many researchers link astigmatism to also be the cause for migraine headaches. Refractive Amblyopia is the easiest to correct.
Some people cannot see properly in one eye because of something blocking the light from entering in. This results in the parts of the eyes to go opaque, this could be due to congenital cataract, corneal haziness or blood clots or a minor tumour caused by the collection of blood vessels (Haemangioma) in the eye. This opacity stops the image input to the eyes and disrupts the visual development. The amblyopia might still persist after the reason for the opacity is taken away from the eye. Deprivation Amblyopia may also be caused by drooping eyelids (Ptosis) or any other problem causing the upper eyelid to block the light from entering the eye. Deprivation Amblyopia is very rare as it occurs in just 3% of the people out of all the cases of amblyopia.
Diagnosis of Amblyopia:
When Amblyopia first occurs, it is hard for the children and their parents to notice the symptoms. It is important that the child gets proper eye check-ups and exams from infancy, even if they don’t show any outward symptoms.
Most of the times the symptoms are noticed during the regular eye exams in the schools. If the child’s eyes do not meet the proper conditions. The teachers or the school nurse refer the parents to an ophthalmologist or an eye specialist to conduct further assessments. These conditions are:
1. The movement of each eye is normal and no random inward or outward movement of the eyes is detected.
2. Both the eyes see normally and can focus on the image equally.
3. The light entering the eyes is not blocked by anything.
The eye doctor will conduct a normal eye exam to check vision in both of your eyes. This includes tests such as:
1. Identifying alphabets and shapes on a board or a chart.
2. Follow a light source with each eye individually and then both of the eyes together.
3. The doctor looking at your eyes using a magnifying device.
Along with these tests, the doctor will also check the visual clarity, muscle strength of the eyes and the focus of your eyes. The doctor will look for wandering of eyes and the differences between the power level of your eyes. For most amblyopia diagnosis only, a normal eye examination is sufficient.
Treatment of Amblyopia:
Treating underlying eye problems is the most effective way to treat amblyopia. This means that you have to help your weaker eye develop normally. In most cases, the measures taken to treat the lazy eye are simple such as contact lenses and eyeglasses.
Detecting and treating the lazy eye at the earliest is the right thing to do. However, diagnosis and treatment of the lazy eye are still possible at an older age. The measures taken to avoid or treat lazy are as follows:
Glasses and Contact lenses
In the case of near-sightedness, far-sightedness and astigmatism in one or both eyes. The doctors will first correct the refractive error between both the eyes. The doctor will provide you with glasses or contact lenses of certain powers to help your eyes with focusing on the object. Glasses and contact lenses help a person with perceiving the depth of an image correctly.
Children with the lazy eye are given an eye patch to wear over their strong or dominant eye. Wearing an eye patch over the strong eye is done so that your weaker eye gets used by the brain. This is also done to strengthen your weaker eye. Wearing an eye patch can be difficult at first but the vision gets better over time, though it takes weeks or months to show proper effect. The doctors will suggest wearing the eye patch two or three hours a day, depending on the severity of the problem in the eye.
In minor cases of amblyopia, the doctor may suggest the use of eye drops such as atropine. This will blur the vision in your strong eye, forcing the brain to use the weaker eye. This is done as an alternative to wearing an eye patch. These eye drops may be used once or twice each day.
If you have cross eyes or eyes that point at different directions, then the doctors might suggest getting an eye surgery. The eye surgery is done to fix the strabismus. The surgery is performed on the muscles of the eyes.
Prevention from Amblyopia:
The key to prevention of lazy eye is to identify the problem. There are many ways to detect the problem. These include a complete ophthalmic examination, visual screenings and tests of binocular functions and stereopsis. The schools should have regular eye examinations in their health and wellness curriculums. The children should be taken for eye exams when they are 6 months old and 3 years old. They should be taken for routinely eye check-ups after the age of 6 years old till they are 18 years old. Early intervention is the best to ensure that the problem does not get worse.
There aren’t many side effects or complications from the treatment measures taken by the doctors. Eye surgery for strabismus may cause many complications in adult patients such as Diplopia or double vision if the eyes are overcorrected, a change in refraction in the eyes may also occur, unsatisfactory alignment of the eyes due to overcorrection or under-correction and allergic reactions to the material used for the surgery may take place. These complications are very rare though, as the people performing the surgery are trained professionals. But there is still a slight chance for these side effects to happen.
There are many myths involving the disorder. The main myths involving amblyopia are as follows:
Myth #1. Many people believe that patching is the only way to fix the lazy eye. There are many new ways and alternatives to fix the lazy eye. For example, use of eye drops for mild cases of amblyopia.
Myth #2. People think that lazy eye cannot be treated after a certain age. Amblyopia can be diagnosed and treated at any age and measures can be taken to prevent the problem from getting worse.
Myth #3. Many people also believe that once the perfect 20/20 vision is achieved, the problem is permanently cured. This is wrong as the chances of the problem resurfacing are still there if proper care of the eyes is not taken regularly.