What is the flatter curve referred to on a toric surface?

The term "flatter curve" in relation to a toric surface refers to the toric base curve. In this context, the base curve is crucial because it determines the overall shape and optical properties of the lens. The toric base curve is designed to correct for astigmatism, which requires two distinct curvatures in the lens.

In a toric lens, the flatter curve specifically refers to one of these two curvatures. Typically, one curvature is more pronounced (steeper), while the other is less so (flatter). This combination allows the lens to effectively address the varying refractive power needed for different meridians of the eye. Correctly identifying the flatter curve as the toric base curve is essential for optimal lens fitting, ensuring that the lens aligns appropriately with the corneal topography.

Understanding this concept is vital for opticians as they design and fit lenses that cater to the specific needs of patients with astigmatism, ensuring both comfort and visual clarity.