Amblyopia (Lazy eye)

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Amblyopia (Lazy eye) : During the visual development period, the best corrected visual acuity of one or both eyes due to abnormal visual experience such as monocular strabismus, anisometropia, high refractive error, and form deprivation is lower than that of normal children of the corresponding age, and there are no organic lesions in the eye examination Called amblyopia. The lower limit of the normal value of vision for children of different ages: the lower limit of the normal value of vision for children aged 3 to 5 years is 0.5, and the lower limit of the normal value of vision for children 6 years and over is 0.7. Amblyopia is an eye disease that seriously harms children’s visual function. If not treated in time, it can cause amblyopia to worsen and even blindness.

1. What is cause or etiology of Amblyopia?

Strabismus amblyopia

Occurs in the monocular, and the child has strabismus or has had strabismus. It is commonly seen in children with monocular and constant strabismus that develops under the age of four. Because the cerebral cortex actively inhibits the visual impulse of strabismus, long-term inhibition forms amblyopia. The difference is generally that the suppression can be released when the squint is injected, while the amblyopia is continuous vision loss. The earlier the age at which strabismus occurs, the faster the inhibition and the greater the degree of amblyopia.

Astigmatic amblyopia

Due to the different vision of the two eyes, the retinal imaging size and resolution of the two eyes are different, and the macular part of the one eye with high diopter is large and blurred, causing insufficient fusion reflex stimulation of the two eyes, which cannot form a single vision of both eyes, resulting in passive suppression, two eyes are flexed If the optical phase is more than 300 degrees, the higher diopters often form amblyopia and strabismus. Even passive and active suppression coexist. The depth of amblyopia is not necessarily related to the degree of anisometropia, but it is related to the nature of gaze. The side and center gaze are more amblyopic. The nature of this type of amblyopia is similar to strabismus amblyopia and is functional and reversible. It is sometimes difficult to distinguish clinically whether amblyopia originates from anisometropia or secondary to strabismus. If this type can be detected early, wearing glasses in time can prevent it.

Refractive amblyopia

It is mostly binocular. It occurs in children or adults with high myopia, myopia and astigmatism without corrective glasses. Most of them have myopia above 600 degrees, hyperopia above 500 degrees, astigmatism ≥200 degrees or both. Binocular vision is equal or similar, and there is no binocular object-image fusion dysfunction, so it does not cause macular functional inhibition. If appropriate glasses are worn in time, vision can gradually improve.

Abolished amblyopia (form deprivation amblyopia)

In infancy, due to ptosis, corneal opacity, congenital cataract, or because the eyelid surgery is too long to cover, the photostimulation cannot enter the eyeball, hindering or blocking the macula from receiving form stimulation, thus causing amblyopia, so Also called blocking visual irritating amblyopia.

Congenital amblyopia or organic amblyopia

Due to macular hemorrhage at birth, the arrangement of cone cells is irregular and occurs before the formation of the eyes of the baby after birth, so the prognosis is not good. Although some of the retina and central nervous system can not detect obvious lesions, they are still considered to be organic lesions, which cannot be found because of existing examination methods. This type is constant amblyopia and the treatment is ineffective.

 

What is Clinical manifestations of Amblyopia ?

Abnormal vision and refraction

The visual acuity between amblyopic eyes and normal eyes is not very clear. Some patients complained of decreased vision, but objective examination showed that the vision was still 1.0 or 1.2. This may be due to the patient’s reduced vision compared to their previous vision. In addition, there may be some obstacles in the visual cells of the central fossa or the subsequent conduction system, there is a very small central dark spot, and there are visual impairments consciously, which cannot be objectively detected.

If there is no organic change in the amblyopic eye, and the visual acuity is above 0.01 and below 0.2, it is often accompanied by abnormal fixation.

The relationship between amblyopia and refractive errors, farsightedness accounts for a large proportion, and myopia has mild amblyopia, so amblyopia is closely related to those with a high degree of hyperopia.

In severe amblyopia of strabismic amblyopia, esotropia is more common than exotropia, which may be due to the earlier onset of esotropia than exotropia.

Difficulty reading

Or crowded phenomenon. When checking vision with the same sight mark, illumination and distance, the distance between the sight marks is different and the measured values ​​are different. Difficulty reading is a characteristic of amblyopia.

The difficulty in reading is that the amblyopic eye is better at recognizing individual optotypes than it is at collecting sets or dense optotypes. That is, the resolution of single-open fonts (such as E) on the eye chart is stronger than that of lines.

Amblyopia only occurs in young children

Binocular amblyopia develops gradually from birth to 9 years old. During this period of development, amblyopia or strabismus can cause amblyopia. After 9 years old, even with the above reasons, amblyopia will not occur.

Amblyopia only occurs in monocular patients

If the two eyes are used alternately, no amblyopia will occur.

Abnormal fixation

People with deep amblyopia often have macular fixation due to poor macular fixation, and often use the omentum next to the macula to fix the macula. Eccentric fixation refers to fixation outside the central fossa. There are many doctrines, but its performance includes parafocal fixation, peripheral fixation, paramacular fixation, and roaming fixation.

What is an examination of amblyopia ?

  1. Visual inspection.
  2. External eye and fundus examination.
  3. Refractive examination.
  4. Check for strabismus.
  5. Fixed nature inspection.
  6. Binocular monocular examination.
  7. Retinal corresponding examination.
  8. Fusion function check.
  9. Stereoscopic inspection.

What is treatment of amblyopia?

Eliminate inhibition, improve vision, correct eye position, and train macular fixation and fusion functions to restore binocular vision. The treatment effect of amblyopia is related to the age and the nature of fixation. It is better for 5-6 years old and worse after 8 years old; center fixation is better, and side center fixation is worse.

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