Which of the following is NOT one of the 3 major types of refractive amblyopia?

• A. Anisometropic amblyopia
• B. Isometropic amblyopia
• C. Torsional amblyopia
• D. Meridional amblyopia

Answer: (C)

Refractive amblyopia is driven by how the eye’s refractive error creates unequal or orientation-specific blur that the brain can’t properly fuse. The three classic patterns reflect how that blur presents between the eyes or across meridians.

Anisometropic amblyopia happens when the two eyes have notably different refractive powers. That disparity makes one eye consistently blurrier, so the brain favors the clearer eye and suppresses the poorer one, leading to amblyopia in the eye with the greater blur.

Isometropic amblyopia occurs when both eyes have high refractive errors that are similar in amount. Because both eyes are blurred equally, the brain has trouble fusing the images and may develop bilateral amblyopia despite the lack of a glaring interocular difference.

Meridional amblyopia is tied to astigmatism, where blur is oriented along a specific meridian. This orientation-specific blur means the brain learns to rely less on information from the blurred meridian, producing reduced acuity for lines in that orientation.

Torsional amblyopia, on the other hand, describes a problem with eye rotation rather than a pattern of refractive blur. It doesn’t fit the framework of major refractive amblyopia types, so it’s not considered one of the three.