In a "plus cylinder" design lens, what is referred to as the base curve?

In a "plus cylinder" design lens, the base curve is defined as the flattest curve on the front side of the lens. This is a crucial element in lens design, particularly for lenses that correct for hyperopia (farsightedness), as the base curve significantly influences the lens's optical performance, fitting, and overall comfort.

The base curve creates a surface that aids in proper light refraction, allowing the lens to accurately focus light onto the retina. Using the flattest curve as a base ensures that the lens provides adequate optical properties while also harmonizing with the natural contours of the wearer's cornea. This alignment is essential for achieving optimal vision correction and comfort.

In a plus cylinder lens, where there are both a spherical and cylindrical component, the distinction between the base curve and other curves becomes particularly important. The base curve typically provides the necessary support needed for the lens's cylindrical component while maintaining proper fit to the eye.