Which refractive error is characterized by two focal points in different meridians?

Which refractive error is characterized by two focal points in different meridians?

• A. Astigmatism
• B. Myopia
• C. Ametropia
• D. Emmetropia

Answer: (A)

Astigmatism is characterized by differing focusing power in different meridians due to an unevenly curved cornea (or lens). Because one meridian has a different focal length than the perpendicular meridian, light from a single point on an object does not converge to one retinal point but to two separate focal points along perpendicular axes. This creates blur and distortion in vision at all distances since only one meridian can be in sharp focus at a time. In contrast, myopia has a single focal point in front of the retina for all meridians, emmetropia means correct focusing with no refractive error, and ametropia is a general term for any refractive error but doesn’t specify two distinct focal points in different meridians.

Astigmatism is characterized by differing focusing power in different meridians due to an unevenly curved cornea (or lens). Because one meridian has a different focal length than the perpendicular meridian, light from a single point on an object does not converge to one retinal point but to two separate focal points along perpendicular axes. This creates blur and distortion in vision at all distances since only one meridian can be in sharp focus at a time.

In contrast, myopia has a single focal point in front of the retina for all meridians, emmetropia means correct focusing with no refractive error, and ametropia is a general term for any refractive error but doesn’t specify two distinct focal points in different meridians.