Which of the following is not a refractive error?

Amblyopia, also known as lazy eye, is fundamentally different from refractive errors like myopia, hyperopia, and astigmatism. While refractive errors occur due to the eye's inability to focus light accurately on the retina, leading to blurred vision, amblyopia is a condition where the brain ignores input from one eye, often because it is improperly developed during childhood.

In contrast, myopia (nearsightedness) happens when the eye is too long or the cornea has too much curvature, causing distant objects to appear blurry. Hyperopia (farsightedness) occurs when the eye is too short or has insufficient curvature, making nearby objects difficult to see clearly. Astigmatism arises from an irregular shape of the cornea or lens that leads to distorted or blurred vision at all distances. These three conditions can often be corrected with glasses, contacts, or surgery, addressing the specific way light is refracted as it enters the eye.

Understanding the distinction between refractive errors and other eye conditions is essential for recognizing the different treatment approaches and implications for visual development and health.