Amblyopia (Amblyopia)
Definition
Amblyopia is defined as a person who has no organic lesions on general ophthalmologic examination and whose corrected visual acuity is ≤0.8 after ciliary muscle paralysis examination.
Etiology
The loss of visual acuity in one or both eyes due to congenital or insufficient light stimulation entering the eye during the critical period of visual development, depriving the macula of the opportunity to form clear images and/or competition between clear and blurred images due to unequal visual input from both eyes (abnormal interaction between the two eyes).
Incidence of amblyopia
Military conscription: 1.0~3.2%
Preschool and school students: 0.5~3.5%
Patients with eye diseases: 4.0~5.3%
General population: 2.0~2.5%
Etiology and classification
1.Strabismic amblyopia
2.Refractive parallax amblyopia
3.Refractive error amblyopia
4.Shape deprivation amblyopia
5.Congenital amblyopia
1.Strabismic amblyopia
Due to the double vision and confusion caused by strabismus, the patient feels extremely uncomfortable and the visual cortical center of the brain actively inhibits the visual impulses transmitted from the strabismic eye, so that the macular function is suppressed for a long time and amblyopia is formed.
Internal strabismus
Constant strabismus in one eye
Inability to fixate vision (peeking at vision check)
Non-common strabismus
One eye movement is obviously restricted (amblyopia is not necessarily a paralyzed eye)
2.Refractive parallax amblyopia
The refractive difference between the two eyes is large (more than 2.50D), resulting in unequal size of the retinal image of the two eyes, fusion difficulties, the visual cortical center can only inhibit the refractive error of the heavier one, the formation of amblyopia over time.
3, refractive error amblyopia
Most patients with bilateral refractive error, such as farsightedness and astigmatism, are unable to obtain clear retinal images without corrective lenses, despite adjustment, resulting in bilateral amblyopia, and after wearing suitable corrective glasses, vision can be gradually improved, but it takes longer.
4.Shape deprivation amblyopia
In infancy, especially in the first 3 months after birth, the development of visual function is inhibited due to corneal clouding, congenital or traumatic cataracts, complete ptosis or overshadowing of one eye, which prevents the visual stimulation of external objects, and form deprivation can lead to severe amblyopia, whose visual prognosis is more serious than strabismic or refractive amblyopia. (Monocular cataract, ptosis, medical origin)
5. Congenital amblyopia?
There are organic lesions, such as neonatal retinal or optic pathway hemorrhage; tiny nystagmus, etc.
Clinical manifestations
1, vision loss
After correction of refractive error
Those with distance visual acuity ≤0.1 are considered severe amblyopia.
0.2-0.5 is moderate amblyopia, 0.6-0.8 is moderate amblyopia.
0.6-0.8 is mild amblyopia.
2.Crowding phenomenon
The ability to distinguish rows of visual markers is poorer than that of a single visual marker, which is called crowding.
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3. Normal light perception
The visual function of the amblyopic eye is abnormal in many ways, such as reduced visual acuity, crowding phenomenon, decreased paracentral gaze and contrast sensitivity, but it has normal visual thresholds in the central recess and periphery, and can detect the faintest light.
Repeat patients
Initial diagnosis suspicious: nystagmus, monocular fixation inability, monocular constant strabismus, monocular deprivation factor,)
Treatment
Clinical practice and animal tests have demonstrated that the sensitive period of the human visual system starts later but lasts longer compared to that of cats and monkeys. In infants, the sensitivity period begins before about 2 years of age, may have passed its peak by 2 years of age, declines substantially until 4 years of age, and then declines slowly until 9 years of age. If there is corneal clouding, congenital or traumatic cataract, longer-term masking of one eye, refractive aberration, high hyperopia and strabismus during the sensitive period, all may cause different degrees of amblyopia, and this period is also the best age to treat amblyopia, so treatment of amblyopia should include
1. correction of refractive error
Early treatment of congenital cataract and congenital complete ptosis.
2. Treatment of amblyopia
The effectiveness of amblyopia treatment is related to the age of treatment and the nature of the gaze, the younger the age, the higher the effectiveness of the treatment for those with central gaze, while in adults the cure is basically hopeless. There are two types of amblyopic eyes: central gaze and paracentral gaze. (Cochlear implant, healthy eye accident)
(1) Central gaze amblyopia
The method of covering the healthy eye and forcing the amblyopic eye to gaze is often used. In order to prevent the occurrence of masked amblyopia, the 3:1 rule should be adopted for 1-year-old children, i.e., cover the healthy eye for 3 days and the amblyopic eye for 1 day, with weekly follow-up. 4:1 rule can be adopted for 2-year-old children, with biweekly follow-up. 3-4-year-old children can have their healthy eye covered for a longer period of time, with monthly follow-up.
(2) Paracentral Gaze Amblyopia
Most people advocate the use of masking method, but some people think that covering the healthy eye makes the paracentral gaze point of the amblyopic eye more solid and oppose it.
Other treatments include augmentation therapy, red filter therapy, and suppression therapy.