A visual defect in which the unequal curvature of one or more refractive surfaces of the eye, usually the cornea, prevents light rays from focusing clearly at one point on the retina, resulting in blurred vision.

• 乱视，像散一种视力缺陷，眼球表示面一点或多点折射时屈光不均，通常为角膜，使光线不能清晰地在视网膜上聚为一个焦点，从而导致视力模糊不清