Amblyopia in children

Amblyopia is a functional reduction in visual acuity caused by the non-use of the eye during visual development. In the affected eye, blindness may develop if amblyopia is not diagnosed and treated prior to the age of 8 years. The diagnosis is based on finding the difference in visual acuity between the two eyes. Treatment of amblyopia in children depends on the cause.

While there is no definitive definition of amblyopia. This term means a reduction in visual acuity that occurs when the normal development of the visual system is disturbed in the so-called "sensitive" period. With the timely detection of this pathology, while the "sensitive" period has not yet ended, the defect has a reversible character. However, the diagnosis at a later date reduces the effectiveness of treatment. It is universally accepted that amblyopia accompanying monocular congenital cataracts does not lend itself to treatment initiated after the first few months of life.

Amblyopia is usually regarded as a unilateral decline in vision, but under certain circumstances, the disorder can have a two-way character. There are at least five separate forms of amblyopia, differing in the etiology of visual deprivation and the bilateral or unilateral nature of the process.

1. One-sided:
   • form of deprivation;
   • strabismus;
   • anisometropia.
2. Two-sided:
   • ametropic (including meridional);
   • form of deprivation.

It is believed that each of these forms has an individual duration of a "sensitive" period. Thus, the possibilities of treatment and its prospects directly depend on the etiology of the disease. So, for example, to obtain an effect in the treatment of anisometropic amblyopia and amblyopia, which arose against the background of strabismus, several years of hard work are necessary, while amblyopia, which has appeared against the background of occlusion, is curable for several months.

[1], [2], [3], [4], [5], [6]

The causes of amblyopia in children

Amblyopia occurs in about 2-3% of children and almost always develops until the age of two.

The brain must simultaneously receive a clear image from each eye. Amblyopia develops if there is a persistent distortion of the visual image from one of the eyes, while the second image has a clear image. The visual area of the cerebral cortex suppresses the visual image from the affected eye.

There are 3 reasons for amblyopia. Strabismus can cause amblyopia, because due to disruption of the location of the eyeballs, various impulses from the retina are sent to the visual cortex of the brain. Similarly, anisometropia (unequal refraction of the two eyes, most often with astigmatism, myopia, hyperopia) leads to a different image on the retina, while the visual image from the eye with a greater error of refraction is less focused. Impaired transparency of the visual axis anywhere between the surface of the eye and the retina (for example, in cataracts) worsen or completely interrupt the formation of the image on the retina of the affected eye.

Symptoms of amblyopia in children

Children rarely complain of a deterioration in the eyesight of one eye. Very small children either do not notice, or can not understand, that their eyes see not the same. Some older children may report a visual impairment on one side or demonstrate a low depth of sensory perception. If the cause is strabismus, the deviation of the eyeball may be noticeable to others. Cataract, which prevents the passage of a light beam through the environment of the eye, can go unnoticed.

Diagnosis of amblyopia in children

Screening for the detection of amblyopia (and strabismus) is shown to all children before admission to school, optimally at the age of 3 years. Photo scoring is one of the methods of screening in very young children and children with developmental delay who are unable to undergo subjective tests. Photo scoring includes the use of a camera to record the image of pupillary reflexes during fixation on the visual object and red reflexes in response to light; the images are then compared, evaluating their symmetry. Screening of older children consists of determining visual acuity using drawing tables (for example, tables with a rotating letter E, Allen table or HOTV table) or Snellen tables.

To identify a specific cause, an additional examination is necessary. Strabismus can be confirmed with eye-closed tests or eye-closing test. Anisometropia can be confirmed by performing a refraction test to assess the refractive power of each eye. Obstruction of the visual axis of the eye can be confirmed with ophthalmoscopy or examination with a slit lamp.

It is desirable to conduct the diagnosis of amblyopia based on the results of a study of visual acuity. In cases where visual acuity is not possible (in young children), the diagnosis is established by the presence of causal factors. For example, monocular congenital cataracts are necessarily accompanied by amblyopia. Therefore, screening for amblyopia is aimed at finding potential amblyogenic factors.

• In early childhood: a bright red reflex from the fundus in both eyes excludes the presence of deprivation amblyopia, accompanying such defects as cataract and opacity of the cornea.
• At the age of 1 to 2 years: evaluation of the symmetry of the brightness of reflexes from the fundus, a test with sequential closure of the right and left eyes, a study of refraction to eliminate strabismus and refractive disorders.
• At the age of 3 to 6 years: the definition of visual acuity, screening for the detection of anisometropic amblyopia, as well as amblyopia against the background of strabismus.

[7], [8], [9], [10]

Treatment of amblyopia in children

The main obstacle to achieving high visual acuity in children with congenital monocular and binocular cataracts is deprivation amblyopia. To achieve a good functional effect, surgical intervention should be performed in the first months of the child's life, and the optic center should remain clean throughout the postoperative period. Periodic examinations are necessary for the purpose of revealing refractive disorders and selecting the appropriate contact lens.

Nevertheless, in a significant number of patients with monocular congenital cataracts treated with this technique, it is not possible to obtain a high visual acuity. Much better results in cases of binocular cataracts, but many patients never achieve normal visual acuity.

For the successful treatment of amblyopia, elimination of the pathology of the organ of vision is required. In most cases, it becomes necessary to occlude the best (fixing) eye. Accordingly, in the treatment of any form of amblyopia, the following objectives are pursued:

1. deprivation form of amblyopia - the release of the optical axis by surgical methods;
2. amblyopia against the background of strabismus - restoration of the correct position of the eye;
3. anisometropic amblyopia - correction of refractive disorders.

The occlusion mode is usually established after checking the visual acuity of both the fixing and amblyopic eyes. Excessive occlusion of the fixing eye can provoke the development of obscurative amblyopia. An alternative to occlusion is the penalization of the fixing eye: this applies cycloplegia of the fixing eye. To increase the effectiveness of pleoptical treatment on the fixing eye, hypermetropic refraction is created. In some cases, this method is preferable, especially in the treatment of amblyopia, developed against a background of strabismus and nystagmus. Conduction of occlusion as an attempt to increase the function is recommended even with the combination of amblyopia with anatomical disorders of the affected eye.

Application of occlusion

The greater the loss of vision in amblyopia, the more difficult it is to treat with occlusion. The inconsistency of therapy through occlusion is the main reason for the low effectiveness of amblyopia treatment, occurring with a frequency of 30-40%. Although there are no reliable techniques for occlusive treatment, in the treatment of children whose occlusion has not produced results, the following rules must be adhered to.

1. Make sure that parents fully understand the purpose and importance of assigning occlusion. Without their sincere involvement, treatment is doomed to failure.
2. If the child is old enough, explain to him the need for prescribed treatment.
3. Wipe the skin before applying the occludor. To protect the skin, colloidal preparations can be used.
4. Occludor is best applied during the sleep of the child.
5. The outer surface of the occludor should be strengthened with an additional layer of adhesive plaster.
6. Use soft cotton gloves with ribbons on your wrists so that the child does not tear off the occluder.
7. Use soft clips for the child's elbows. They can be made of cardboard or other non-traumatic materials.
8. Praise your child and encourage him in other ways when there is a positive occlusion.
9. Do not forget to emphasize the need for occlusion every time a child is examined.

[11], [12], [13], [14], [15], [16]

Monocular form of deprivation

Most researchers recommend surgical intervention in the first 2-3 months of life for obtaining high visual acuity. In the postoperative period, optical correction and occlusion should be prescribed without delay. Partial occlusions (50-70% of the entire waking time) is prescribed to avoid the risk of developing obturation amblyopia of the fixing eye and, more importantly, the induction of nystagmus on the fixing eye.

The binocular form of deprivation

If surgical intervention and rehabilitation measures are performed in a patient with bilateral congenital cataracts in the absence of nystagmus, the risk of developing deprivational bilateral amblyopia is practically absent. However, with the appearance of nystagmus, visual acuity is greatly reduced, even against intensive treatment. In many cases of binocular deprivation there is also a monocular form and, to equalize the visual acuity, it becomes necessary to conduct occlusion of the leading fixing eye. Complications of cataract surgery in children are very important and are often incomparable with the complications that arise in adult patients. These complications include the following.

• Amblyopia. As already mentioned, amblyopia is the main obstacle to achieving high visual acuity with monocular and binocular congenital cataracts. The cause is, caused by cataracts, the occlusion of the optical axis. In addition, additional factors provoking the development of amblyopia, may be anisometropia and strabismus.
• Turbidity of the capsule. Oppression of the posterior capsule in young children occurs in almost 100% of cases and occurs during the first few weeks or months after surgery. That is why, in order to avoid the need for a posterior capsulectomy in the postoperative period, the technique of lenvitretomy was introduced.

With the use of aspiration techniques in the postoperative period, there is often a need for laser-assisted posterior capsuleectomy.

• Edema of the cornea. Immediately after cataract surgery in children, especially when using an intrastromal infusion cannula, corneal edema may mild. In most cases, edema does not persist for long and disappears spontaneously.
• Cystic macular edema. Reports of its occurrence in children are rare.
• Endophthalmitis. Endophthalmitis, although rare, is encountered in pediatric cataract surgery. Surgical intervention against the background of obstruction of the nasolacrimal canal, respiratory infection of the upper respiratory tract or pathology of the periorbital skin predispose to the development of complications. The functional result in these patients is usually poor. Glaucoma. The main complication in patients of childhood with aphakia. Its prevalence in congenital cataracts can reach 20-30%. The risk of complications increases with combined microphthalmia, PGPS and nuclear cataract. May not manifest itself within a few years after the operation. For the early detection of glaucoma, regular measurements of intraocular pressure, examination of the optic nerve disk and examination of refractive error are recommended. A rapid decrease in hypermetropic refraction of the aphakic eye suggests the possibility of the appearance of glaucoma. The results of treatment of aphakic glaucoma in children remain unsatisfactory.
• Irregular pupil shape. Disturbance of the pupil shape is a frequent consequence of cataract surgery in children, but it does not have much significance for the functional result of the operation. In a number of cases, with interference with CGPP, damage to the iris can occur at the time of removal of the rigid membrane tissue and the associated traction of the ciliary processes.
• Nystagmus. Bilateral nystagmus is observed in a significant number of children with bilateral congenital cataracts. Supposes the presence of binocular deprivation amblyopia. Nystagmus is also found in patients with monocular congenital cataracts. It can be either unilateral or bilateral, but in both cases, the presence of nystagmus worsens the prognosis.
• Retinal disinsertion. The prevalence of retinal detachment in children with aphakia decreased after two decades ago the technique of lenvitretomy appeared. However, it is necessary to recall the results of previous studies with other types of surgical technique for lens removal, which emphasize that detachment of the retina may not manifest itself for three or even four decades. Thus, the conclusion about a low risk of retinal detachment during lenсwetectomy in patients with congenital cataracts can only be made after a long observation.
• Strabismus (usually convergent) is often present in children with monocular congenital cataracts. Can occur after removal of the lens. Although strabismus is rare before the operation for a bilateral congenital cataract, it can manifest itself in the postoperative period. Strabismus is an additional amblyogenic factor in the problem of visual rehabilitation of these patients.

Functional Results

Over the past two decades, functional results have significantly increased with congenital and progressive cataracts. This is due to a combination of several factors - an emphasis on early detection of cataracts, improvement of surgical technique, improved quality and greater accessibility of contact lenses, and, in some cases, implantation of intraocular lenses. In congenital cataracts, a special and most important factor determining the visual effect of an operation is the early detection of the disease, which emphasizes the need for a special examination by a direct ophthalmoscope or retinoscope of all newborns to eliminate opacity in the lens. Despite the fact that presently with bilateral congenital cataracts a good visual effect is achieved, and blindness and serious visual disorders as a result of surgery are rare, bilateral congenital cataract is still a significant problem.

The results of treatment of patients with monocular congenital cataract are worse, but they also provide hope. The most important postoperative complication leading to a reduction in the initially high visual acuity is glaucoma.

Amblyopia in children can become irreversible if it is not detected and untreated before the child reaches the age of 8, the time when the vision system ripens. For most children with amblyopia, when it is detected and treated before the age of 5, there is a slight improvement in vision. Early treatment increases the likelihood of complete recovery of vision. Relapse is possible in certain cases until the time when the vision system ripens.