What Is Meridional Amblyopia?

The common nonmedical term "lazy eye" is used for the condition ambylopia because the eye with poor vision seems to be not working properly. The Free Dictionary defines ambylopia as “an uncorrectable decrease in vision in one or both eyes with no apparent structural abnormality seen to explain it.” It is a diagnosis of exclusion, meaning that when a decrease in vision is detected, other causes must be ruled out.

Condition

• Amblyopia is a common medical condition of the eye, responsible for reduced vision in around two to four percent of the population. Good vision requires visual acuity, or clarity of images, at the eye and the processing of these images by the brain. If the image formed by both eyes is significantly different, the brain can get confused during image processing and may not be able to correctly fuse the image from each eye into one image. In this situation the brain will suppress the less clear image; the function of that eye seems to be decreased.

Causes of Amblyopia

• Amblyopia usually occurs during the development stage of visual acuity in early childhood. Strabismus, a misalignment of the eyes (the two eyes are looking in two different directions at the same time), is the most common cause of functional amblyopia.

Anisometropia and Astigmatism

• Anisometropia is a result of a difference of refractive states between the two eyes; the brain cannot fuse the two dissimilar images. Astigmatism is a refractive error in a particular plane of vision, and results in meridional amblyopia.

Complications

• Ptosis, the drooping of the eyelid, may cause improper image formation by that eye. Opacification of the lens of the eye may occur in children suffering from some medical syndromes; this hampers the growth process of vision development.

Meridional Ambylopia

• Meridional amblyopia is caused due to an uncorrected large astigmatism during the amblyogenic period of visual development. Children born with a high degree of astigmatism, who are unable to see an image in a particular plane of vision, retain permanent abnormality of vision in that plane even if treated at a later date with astigmatism-correcting cylindrical lenses. Vision in other meridians will remain normal, and will affect only the meridian initially having the astigmatic defect.