The critical period of visual development is before 2 years of age (before 3 years of age) and the sensitive period of visual development is before 8 years of age (5 years of age, 13 years of age). During this stage, the visual environment influences the development of the visual system, which shows an extraordinary sensitivity to abnormal stimuli. A poor visual environment predisposes to amblyopia, especially during the critical period of visual development, but it is also the best age to treat amblyopia.
In April 1996, the National Amblyopia and Strabismus Control Group of the Chinese Academy of Ophthalmology defined amblyopia as a condition in which there is no obvious organic lesion in the eye, but functional factors are the main cause of hyperopia <0.9 and cannot be corrected.
Classification of amblyopia
(A) Classification according to the degree of amblyopia
1, mild amblyopia: corrected visual acuity of 0.8 to 0.6.
2, moderate amblyopia: corrected visual acuity of 0.5 to 0.2.
3.Severe amblyopia: corrected visual acuity <=0.1.
Here, visual acuity refers to corrected distance visual acuity.
(B) Etiological classification
They are form deprivation amblyopia, strabismic amblyopia, refractive error amblyopia, refractive error amblyopia and others.
1. Form vision deprivation amblyopia
In infancy, due to refractive interstitial clouding, severe ptosis, and inappropriate masking, light stimuli cannot enter the eye normally, depriving the macula of the opportunity to receive clear image stimulation and causing serious impairment of visual function development. Three factors influence the degree of form deprivation amblyopia: (1) the age at which form deprivation begins; (2) the duration of form deprivation; and (3) the mode and degree of form deprivation (complete or partial, monocular or binocular). This type of amblyopia is mostly severe, difficult to treat, and has a poor prognosis. Early detection of possible causes and early treatment (etiology, amblyopia). For example: early surgery for congenital cataract; timely optical correction; avoidance of medically induced form deprivation; effective visual acuity monitoring after etiologic treatment.
2.Strabismic amblyopia (strabismic amblyopia)
The patient has strabismus or has had strabismus. The strabismus causes double vision and visual confusion that makes the patient extremely uncomfortable. The visual cortex of the brain actively inhibits the visual impulses transmitted from the macula of the strabismic eye, and the macular function of the strabismic eye is suppressed for a long time, and amblyopia is formed. Amblyopia occurs in the strabismic eye with monocular amblyopia. The clinical characteristics of strabismic amblyopia are.
(1) early onset (<2 years old), long duration, constancy, and monocular strabismus predispose to amblyopia with a high degree of severity; the size of the strabismic eye is not related to the degree of amblyopia. < p="">
(2) Internal strabismus is more frequent than external strabismus, and the degree of amblyopia is more severe.
(3) Eccentric gaze and abnormal retinal correspondence are the difficulties in the treatment of strabismic amblyopia.
3.Refractive amblyopia (anisometropic amblyopia)
Even if the refractive error is corrected, the image size caused by the refractive error is still unequal, which makes it difficult or impossible to fuse the two eyes into one, and the visual cortex inhibits the function of the heavier side of the refractive error, resulting in amblyopia. Monocular amblyopia. The clinical characteristics of refractive error amblyopia are
(1) hyperopia and astigmatism are easy to form amblyopia, the two account for about 97%; the degree of amblyopia is related to the degree of refractive parallax; moderate and low myopic refractive parallax is not easy to cause amblyopia, high myopia has pathological changes, low vision is not amblyopia.
(2) Positive eye position.
(3) Central or paracentral concave gaze.
(4) Better prognosis, more peripheral fusion and rough stereopsis.
(5) If no screening is performed, it is mostly detected late.
(6) Treatment: optical correction, suppression of the dominant eye.
4.Refractive amblyopia (ametropic amblyopia)
It occurs in patients with high refractive error who have not worn corrective glasses. It is mostly seen in hyperopic and astigmatic eyes, and the broad form of deprivation prevents the normal development of visual function and forms amblyopia. Refractive errors are mostly: hyperopia > 3.00 D, myopia > 6.00 D, astigmatism > 2.00 D. The clinical characteristics are
(1) Bilateral: visual acuity (sc, cc) of both eyes are equal or close; no significant refractive aberration.
(2) Positive eye position: there is no competition between the two eyes, so it does not cause macular function inhibition.
(3) Treatment is based on optical correction, and the prognosis is good.
Prevention and treatment of amblyopia
We should pay attention to prevention and create a good visual environment for infants and children. Early detection and treatment of eye diseases affecting visual development, such as congenital cataract, severe ptosis, strabismus, etc. Early monitoring and early intervention. That is, early detection and early treatment. Screening for amblyopia: the target population is children; a large sample or overall screening should be performed; and professionals are required to screen for amblyopia in a correct and uniform manner. The prognosis of amblyopia is closely related to the age of treatment; the younger the age, the better the outcome, which is often affected by too late detection. The principle of amblyopia prevention and treatment is early detection, early treatment, and should not wait.
(A) Evaluation criteria for the efficacy of amblyopia treatment
According to the evaluation criteria of the National Amblyopia and Strabismus Prevention and Treatment Group of the Chinese Academy of Ophthalmology in 1996.
1, ineffective: regression, unchanged or only 1 line improvement in visual acuity.
2.Progress: visual acuity improvement of 2 lines or more.
3.Basic cure: visual acuity improved to 0.9 or more.
4.Cure: after 3 years of follow-up, the vision remains normal.
If available, surgically correct the eye position and receive monocular function training in both eyes in order to achieve the ideal cure and establish monocular function in both eyes. The International Standard Visual Acuity Scale is recommended. Visual acuity refers to corrected distance vision.
(ii) Establishment of stereopsis
Stereopsis is the highest form of binocular monovision, and the establishment of stereopsis is the ideal goal of amblyopia treatment. However, the establishment of stereopsis is influenced by many factors.
(1) Degree of amblyopia: severe amblyopia has the worst prognosis, while there is no significant difference in the percentage of stereopsis obtained in moderate and mild amblyopia.
(2) Type of amblyopia: refractive amblyopia has the best prognosis; form-deprived amblyopia has the worst prognosis; strabismic amblyopia is likely to have less stereopsis and is related to the age of onset and treatment.