Paediatric hyperopia, accommodative esotropia and refractive amblyopia

Amblyopia is the most common cause of reduced vision in children and young people, affecting approximately two to three per cent of the population. Amblyopia is the consequence of disruption of the normal neurological development of the visual system and can occur with varying levels of severity. Clinically, amblyopia is diagnosed when there is a difference in visual acuity between the eyes of two or more logMAR lines and there is no sign of ocular or visual pathway disease. Careful examination using best practice techniques of the anterior segment and adnexa and of the posterior segment through dilated pupils is required to seek signs of other underlying ocular pathology. Amblyopia is usually classified according to the underlying cause. The most common causes are strabismus (misalignment of the eyes), anisometropia (significant difference in refractive error between eyes) and form deprivation (presence of medial opacity, such as cataract). Unilateral or bilateral amblyopia can arise secondary to a significant bilateral refractive error, while meridional amblyopia can arise from a significant astigmatic refractive error. These conditions create monocular blur or ocular misalignment, which if present during the critical period of visual development (up to about seven years of age)1 can lead to a loss or rearrangement of neural connections within the visual cortex. The relationship between strabismus and amblyopia is complex in that, as well as being a cause of amblyopia, strabismus and anisometropia can also both arise as a result of amblyopia