Clinical aspects of different types of amblyopia

Amblyopia is a deficit of vision, principally visual acuity, not immediately correctable by glasses, in the absence of ocular pathology, due to interruption of normal visual development during a sensitive period in childhood. Amblyopia occurs before 6–8 years of age. It may be completely or partially treated by modulation of the visual input during a sensitive period of visual development. The duration of this period varies depending on the cause of amblyopia . Amblyopia is the leading cause of visual impairment in children affecting up to 5% of general population 5, . Population prevalence depends upon the fact if there have been any interventions to prevent or treat the condition, or not. Diagnosis is based on a reduction in best corrected visual acuity by testing visual acuity in each eye separately with a line of symbols with appropriate effect of crowding, and after exclusion of ocular pathology . The acuity testing procedure and refraction must be accurate, and the age related norms must be known for the vision test used. Amblyopia is defined in terms of visual acuity, but other visual functions are affected as well. It is important to recognize that a finding of reduced visual acuity in a child is not a diagnosis of amblyopia. Amblyopia is only found in the setting of a causative factor. If no obvious amblyogenic factor is found on examination, then either the reliability of the visual acuity measurement should be questioned or subtle ocular pathology such as optic nerve hypoplasia or macular disease should be considered .