Which type of astigmatism typically requires a toric lens for correction?

Toric lenses are specifically designed to correct astigmatism, which is a refractive error caused by an irregular curvature of the cornea or lens. Astigmatism can be categorized into different types based on the orientation of the steep and flat meridians of the eye.

With-the-rule astigmatism occurs when the vertical meridian is steeper than the horizontal meridian. Against-the-rule astigmatism, on the other hand, has a horizontal meridian that is steeper than the vertical. Mixed astigmatism involves a combination of both with-the-rule and against-the-rule characteristics, where one meridian is hyperopic (farsighted) and the other is myopic (nearsighted).

All types of astigmatism—whether with-the-rule, against-the-rule, or mixed—can benefit from correction with toric lenses. These lenses have different powers in different meridians, which allows them to compensate for the irregularities in the eyes' shape. Thus, toric lenses are versatile in addressing the needs of patients with varying types of astigmatism.