Amblyopia is caused by abnormal visual experience (monocular strabismus, refractive aberration, high refractive error, form deprivation) during the visual developmental period when the best corrected visual acuity in one or both eyes is lower than that of a normal child of the same age, with no organic pathology on ocular examination. Yongliang Li, Studio Ophthalmology
Features.
1. Poor visual acuity: best corrected visual acuity in one or both eyes is lower than that of normal children of the same age (the level of visual acuity development varies according to the age of the child, the lower reference value of normal visual acuity: 0.5 for 3 years old, 0.6 for 4-5 years old, 0.7 for 6-7 years old, and 0.8 for 7 years old and above.) The difference between the best corrected visual acuity of both eyes should not exceed two lines, otherwise the worse one is amblyopic.
2. Crowding phenomenon: the amblyopic eye’s ability to discriminate between rows of visual markers is worse than the ability to discriminate between individual visual markers due to contour interference, i.e., the visual acuity of a single visual marker is higher than the visual acuity of rows (the visual acuity examination of amblyopia is based on the standard of row visual acuity).
3. Paracentral gaze: Some patients with severe amblyopia lose the ability to focus on the central macular sulcus due to severe vision loss, forming paracentral gaze. (Treatment of amblyopia is different for central gaze and paracentral gaze)
4. visual evoked potentials: manifested by prolonged PVEPP latency and decreased amplitude, which is significant with increasing spatial frequency.
5. Abnormalities in contrast sensitivity.
The understanding of amblyopia includes at least the following.
1. onset during visual development, amblyopia is a developmental rather than a congenital disorder, and the possibility of cure exists during the developmental period when it occurs.
2. caused by abnormal visual experience, with a clear etiology: monocular strabismus, refractive error, high refractive error, and form deprivation
3. the best corrected visual acuity is lower than that of a normal child of the same age
4. no vision-related organic pathology is present
5. the characteristics of amblyopia are present
Therefore, the diagnosis of amblyopia should be made carefully, and a complete and systematic examination and comprehensive analysis are indispensable for the acquisition of medical history, the search of etiology, the exclusion of organic pathology, and the matching of amblyopic features; the diagnostic examination of amblyopia should include external eye examination, refractive interstitial examination, fundus examination, visual acuity and intraocular pressure examination, eye position and eye movement examination, stereopsis and synoptic examination, refractive state examination, PVEP examination, contrast sensitivity examination, and contrast sensitivity examination. PVEP examination, contrast sensitivity examination, etc. Amblyopia should not be rashly diagnosed based on visual acuity and simple eye examinations alone.