What is the total diameter of a bicurve lens with an 8.5 mm base curve and a 1.2 mm peripheral curve?

To determine the total diameter of a bicurve lens, you add the measurements of the base curve and the peripheral curve. The base curve, which in this case is 8.5 mm, forms the central part of the lens, while the peripheral curve, at 1.2 mm, represents an additional portion that will extend outward from the base curve.

When calculating the total diameter, it is essential to consider that the diameter is a total measurement across the widest part of the lens. In this instance, the calculation involves adding the base curve and the peripheral curve directly to each other:

8.5 mm (base curve) + 1.2 mm (peripheral curve) = 9.7 mm.

However, for a bicurve lens, this adds additional width to each side of the lens. Thus, the full diameter is 8.5 mm + 1.2 mm + 1.2 mm (to account for both sides of the lens). This results in a total diameter of 11 mm. Therefore, the correct choice reflects this measurement.

Understanding this principle is crucial for lens fitting as it helps practitioners determine appropriate lens sizes based on the curvature and overall design of the lens.