What condition is characterized by irregular focus of light rays on the retina?

Astigmatism is indeed characterized by the irregular focus of light rays on the retina. This condition arises when the cornea or lens has an uneven curvature, leading to distorted or blurred vision. In astigmatism, light rays entering the eye do not converge at a single focal point, causing difficulty in seeing fine details both at various distances and angles.

Understanding astigmatism's impact on vision is crucial, as it can affect various aspects of daily life, necessitating corrective measures such as glasses or contact lenses specifically designed to compensate for the irregular curvature.

In contrast, monochromatism is a condition related to color vision deficiency, cataracts lead to clouding of the lens which affects clarity of vision but not directly involved with the focus of light rays, and hyperopia (farsightedness) means light focuses behind the retina, typically due to an eyeball that is too short or a lens that is too weak. Each of these conditions affects vision differently from how astigmatism uniquely impacts the focusing of light on the retina.