Which of the following is a vision defect?

Astigmatism is indeed classified as a vision defect. It occurs when the cornea or lens of the eye has an irregular shape, causing blurred or distorted vision. This condition affects the eye's ability to focus light properly on the retina, resulting in visual disturbances at various distances.

In contrast, aphasia refers to a language disorder that affects a person's ability to communicate. Caries, commonly known as dental cavities, pertains to tooth decay and oral health rather than visual acuity. Toxemia is a medical condition related to the presence of toxins in the blood, typically associated with pregnancy complications such as preeclampsia. None of these conditions affect vision in the way that astigmatism does. Understanding these differences clarifies why astigmatism is the correct choice for identifying a vision defect.