How many curves does a front toric lens have?

A front toric lens is designed to correct astigmatism, which is a common refractive error caused by an irregular shape of the cornea or lens. The crucial aspect of a front toric lens is that it includes both spherical and cylindrical components to address the unique visual needs associated with astigmatism.

The correct characterization of a front toric lens is that it has one spherical curve and one cylindrical curve. The spherical curve provides the basic power needed for distance vision correction, while the cylindrical curve targets the specific meridian requiring additional correction due to astigmatism. This combination allows for effective vision correction in individuals with different refractive needs across various lines of sight.

In contrast, other choices do not accurately depict the structure of a front toric lens. While it may seem like two cylindrical curves would also address astigmatism, the essential requirement includes both a spherical and a cylindrical component. The mention of three curves or just one spherical curve fails to capture the complexity and functionality of a front toric lens. Understanding this structure is fundamental for both fitting and assessing the effectiveness of toric lenses in patients with astigmatic errors.