The area between the two focal points of a spherocylindrical lens is called the conoid of?

The area between the two focal points of a spherocylindrical lens is known as the conoid of Sturm. This term describes a geometrical shape that arises in optics due to the varying focal points of the lens, which has both spherical and cylindrical components, typically used to correct astigmatism.

In a spherocylindrical lens, there are two principal meridians with distinct focal points. The conoid of Sturm represents the area where light rays converge between these two focal points, illustrating how the lens creates different levels of convergence depending on the orientation of incoming light. Understanding this concept is crucial when fitting lenses, as it helps describe the behavior of light as it passes through the lens and the resultant visual effects for the patient.

The other choices represent terms related to optics but do not specifically describe the unique behavior of a spherocylindrical lens's focal area. Aberration refers to defects in image formation, focus relates to the convergence of light without specific mention of cylindrical lenses, and diopter is a unit of measurement for optical power, none of which capture the specific relationship between the focal points in a spherocylindrical lens setup.