For more than ten years, we have been using the diagnosis standard of amblyopia, which was adopted at the working meeting of the National Amblyopia and Strabismus Prevention and Control Group in April 1996, as the diagnosis standard of amblyopia: “All children with amblyopia without obvious organic lesions and with functional factors causing distance visual acuity ≤ 0.8 that cannot be corrected”. Because this diagnostic criterion does not reveal the essence of amblyopia, it has led to the expansion of the diagnosis of amblyopia, which has caused many healthy children to join the ranks of amblyopia and receive long time amblyopia training, not only wasting limited public medical resources, but also causing more or less impact on the young children’s body and mind.
In this paper, we use the five-year medical textbook “Ophthalmology” (7th edition, People’s Health Publishing House) as the main basis to interpret the connotation and changes of amblyopia diagnostic criteria.
I. Comparison of the old and new diagnostic criteria
1. The traditional definition of amblyopia
Amblyopia is defined as amblyopia in which there is no obvious organic lesion in the eye and the distance visual acuity is ≤0.8 and cannot be corrected mainly due to functional factors.
Diagnostic points: (1) no obvious organic eye lesions; (2) corrected visual acuity ≤ 0.8.
2.The latest definition of amblyopia
The best corrected visual acuity of one or both eyes is reduced due to abnormal visual experience (monocular strabismus, refractive aberration, high refractive error and form deprivation) during the visual development period, and there is no organic lesion in the eye examination.
Diagnostic points: (1) occurring during visual development; (2) presence of abnormal visual experience; (3) loss of best-corrected visual acuity; (4) no organic pathology on ocular examination.
3. Changes in the new diagnostic criteria
(1) Focus on the relationship between corrected visual acuity and age
The new criteria pay more attention to the differences in visual development, and fully take into account the existence of underdeveloped or delayed vision in younger children. This can avoid the expansion of amblyopia diagnosis and the resulting over-treatment.
(2) Focus on the role of “abnormal visual experience” in the diagnosis
The term “abnormal visual experience” actually refers to the cause of amblyopia (risk factors for the development of the disease), which includes several common forms such as monocular strabismus, refractive error, high refractive error, and form deprivation. In the new criteria, it is recommended to actively search for abnormal visual experiences (risk factors) that cause amblyopia in cases to be diagnosed as “amblyopia”. In cases where no such “abnormal visual experience” exists, further testing should be done to rule out optic pathology, intracranial pathology, hysteria, or pseudohypopthalmia, rather than making a hasty diagnosis of “amblyopia”.
Some patients with optic pathology or intracranial pathology may have abnormal visual acuity, while the patient’s eyes generally do not have organic pathology, so according to the traditional diagnostic criteria, they are included in the category of “amblyopia”, resulting in the underdiagnosis of important diseases and delayed treatment. In clinical practice, we encounter some cases of low vision in which auxiliary examinations (e.g., ocular electrophysiology, cranial CT, etc.) fail to detect the lesion, which used to be called “congenital amblyopia” or amblyopia of unknown origin. However, in recent years, clinical and research studies have found that these patients may be suffering from hysteria, pseudo-hypopthalmia, or certain diseases that we do not know yet. Therefore, for these patients, many scholars prefer the idea of “close follow-up” rather than including the diagnosis of “amblyopia”.
Amblyopia diagnostic criteria: 1.
1. Period of amblyopia: during the period of visual development (diagnostic condition Ⅰ).
The sensitive period of children’s visual development is 0-12 years old, and the critical period is 0-3 years old, during which (before visual maturity) various abnormal visual experiences can lead to the occurrence of amblyopia. In other words, after the age of 10 to 12 years, the patient’s visual development is generally “mature” and new “abnormal visual experiences” do not lead to “amblyopia”. Therefore, in clinical cases with abnormal corrected visual acuity, if there is evidence of previous normal visual acuity (visual acuity examination records, etc.), the diagnosis of “amblyopia” should not be valid, and other causes of abnormal visual acuity should be actively sought.
2. Abnormal visual experience (diagnostic condition II)
“Abnormal visual experience” refers to the etiology of amblyopia (i.e. risk factors for the development of the disease), mainly including
(1) Monocular strabismus: It is one of the most common causes of amblyopia, which is caused by the suppression of the strabismic eye by the gaze eye. In alternating strabismus, both eyes have equal access to visual information in the macula, which generally does not cause amblyopia.
2) Refractive aberration
Due to the large refractive aberration between the two eyes, the macula forms objects of unequal size and clarity, and the one with larger refractive power has form deprivation, leading to the occurrence of refractive aberration amblyopia. The difference between the two eyes is 1.50D in the spherical lens and 1.00D in the column lens, which can make the higher refractive error form amblyopia.
(3), high refractive error
a: moderate, high hyperopia: hyperopia 4.50DS or more (dominant hyperopia +2.00DS to +3.00DS) may cause amblyopia, and the severity of amblyopia is positively related to the degree of hyperopia.
b: Ultrahigh myopia: Patients with low to moderate myopia generally do not have amblyopia because the affected eye can receive visual information at close distances, but only ultrahigh myopia above -8.00DS to -10.0DS is a risk factor for amblyopia.
c:Astigmatism: Astigmatism above 2.00DC can cause amblyopia.
Amblyopia caused by refractive error is the more common type, among which hyperopic astigmatism is the most common. Common degree: hyperopic astigmatism > high hyperopia > moderate hyperopia > ultra-high myopia.
4) Formal deprivation
It mostly occurs in cases of refractive interstitial clouding (e.g., congenital cataract, corneal clouding), ptosis, and medically induced eye shielding. Amblyopia is formed when the macula is deprived of the opportunity to form clear images due to insufficient form stimulation. Studies have found that even 3-7 days of inappropriate monocular masking in infants and children can lead to irreversible amblyopia, which should be brought to the attention of ophthalmologists and related personnel.
3.Corrected visual acuity is lower than normal children of the same age (diagnostic condition III)
1) Corrected visual acuity and correction method: The visual acuity in the amblyopia diagnostic criteria is “corrected visual acuity”, and it is the corrected visual acuity of general optometry (such as the visual acuity of wearing frame glasses), not the visual acuity of unconventional correction methods such as comprehensive optometry or RGP, which do not represent the actual daily visual acuity.
(2), corrected visual acuity non-fixed values: no longer 0.8 as the only criterion for the diagnosis of amblyopia, need to fully take into account the presence of under-parenting or delayed development of visual acuity in younger children, the age of infants and young children and the lower limit of normal visual acuity are as follows
Table I Lower limit of visual acuity reference values for young children
Age
Lower limit of visual acuity reference value
3 years
0.5
4 to 5 years old
0.6
6 to 7 years old
0.7
7 years old and above
0.8
(3), the difference between the two eyes is more than two lines: this is a more special case, less common. If the visual acuity of both eyes is 5.3 and 5.0 respectively, the possibility of amblyopia should also be considered in 5.0 eyes.
4.No organic lesion in the eye (diagnostic condition Ⅳ)
The absence of significant organic pathology in the eye should be understood as the absence of significant organic pathology in the eye, the posterior visual pathway and the intracranial visual center.
The refractive media and fundus examination are relatively simple and are mandatory for the diagnosis of amblyopia, but the presence of lesions in the optic pathway and intracranial area often requires non-conventional ancillary examinations such as VEP, visual field and cranial CT to be clarified. Generally speaking, for those who meet conditions I-III and no abnormalities are seen in the eye examination, the diagnosis is basically clear and no further investigation of cranial CT is needed. For suspicious cases (e.g., no obvious abnormal visual experience), it is necessary to consider whether other relevant examinations are needed according to the specific situation.
Ideas of amblyopia diagnosis
The following table shows the conditions that need to be met for the diagnosis of amblyopia, which is also our clinical diagnosis idea and process: A clear diagnosis of amblyopia requires that all conditions I, III and IV are met, and one or more of II are met. Otherwise, the diagnosis of “amblyopia” should not be made, especially for those with low corrected visual acuity who lack the corresponding “abnormal visual experience”, and other causes should be further investigated.
Diagnosis idea
Diagnosis conditions
Does it meet
I. Period of occurrence: During the period of visual development
Conformity?
Ⅱ. Abnormal visual experience (risk factor)
1 Monocular strabismus
Consistent with?
2 Refractive aberration
3High refractive error
a moderate, high hyperopia
b super high myopia
c moderate or higher astigmatism
4Shape deprivation
Ⅲ. Low corrected visual acuity
Consistent with?
IV. No organic lesions in the eye
Consistent with?
IV. Several factors supporting the diagnosis of amblyopia
1. Crowding phenomenon
Crowding phenomenon refers to the refractive correction of amblyopic patients, the corrected visual acuity of single vision marker is 1-3 lines better than the whole line of vision marker, mainly in the corrected visual acuity of comprehensive optometry (usually with single vision marker) is better than the corrected visual acuity of insert optometry (usually with fixed light box vision table). This is a clinical characteristic of amblyopic patients, in turn, the presence of “crowding phenomenon” is one of the supporting factors for the diagnosis of “amblyopia”.
2. Diagnostic treatment
In some cases of amblyopia (where the diagnosis is unclear and other diagnoses are ruled out, such as amblyopia of unknown origin), diagnostic treatment is generally provided in accordance with the criteria for the treatment of amblyopia, with close follow-up. If the treatment is effective, the diagnosis of amblyopia is supported; otherwise, the diagnostic idea needs to be changed to find other causes of low vision.
V. Considerations for the diagnosis of amblyopia
1. Combination of other pathologies.
Some patients with obvious refractive abnormalities or eye position abnormalities may be combined with congenital fundus lesions, which can generally be clarified by fundoscopic examination. However, because some younger children do not cooperate with fundoscopic examination, other fundus diseases may be missed.
2. Is there a “congenital amblyopia”?
In some books, unexplained amblyopia is categorized as “congenital amblyopia”. The author believes that before making the diagnosis of “congenital amblyopia”, two questions should be clarified: (1) When did the low vision start to occur? (2) How long did the low vision last and did it change? The possibility of “congenital amblyopia” can only be considered if the “low vision” condition has been present since childhood and has not changed significantly over a long period of follow-up. In clinical practice, the diagnosis is confusing because young children are unable to describe the exact time of poor visual acuity. In addition, since these patients do not have the “abnormal visual experience” that causes amblyopia, it is likely that other causes exist that are not yet recognized, and they can be classified as “amblyopic suspects” and followed closely.
Amblyopia is a common childhood eye disease that, if left untreated, will have a great impact on the patient’s learning and employment. With a lot of publicity in recent years, parents, ophthalmologists and related health care doctors are paying more and more attention to amblyopia, but the consequent generalization of diagnosis and overtreatment lead to the waste of public medical resources, increase the financial and mental burden of patients’ families, and even bring physical and mental harm to the affected children. Therefore, as front-line personnel in children’s eye care, we should learn and appreciate the criteria of amblyopia diagnosis, keep our diagnosis “off”, and reduce misdiagnosis and missed diagnosis.