Volk University: Lenses, Lenses and More Lenses

Welcome to “Volk University” where we invite you to learn more about the selection, use and care of your favorite Volk products.






Today’s lesson – Lenses. What’s special about Volk lenses and what’s the difference between the more than 180+ lens options we offer.


Volk Lens Basics

  • Volk lenses are aspheric on both sides of the lens-many other lenses are only aspheric on one side. An aspheric surface delivers a crisper image to eliminate distortion. Volk’s double-aspheric lenses eliminate more distortion for better overall imaging.
  • The Diopter value of a lens is a unit of refractive power of an optical lens, and is denoted by the inverse of the focal length of the lens.
    • A lens with a higher Diopter power provides a wider field of view, lower magnification, and the best performance through small pupils.
    • Lenses with a lower Diopter power have a narrower field of view, higher magnification, and do not perform well through a small pupil.


  • Lens orientation makes a difference.
    • Double aspheric lenses are not always symmetric on both sides. A lens with asymmetric aspheres will produce different optical results depending on which side of the lens you look through. Therefore, proper orientation is required for peak performance.
    • The Volk “V” is like an arrow and is designed to point towards the patient. Orient your lens with the point of the V pointing at the patient.
    • Some lenses have a silver rim on one side of the ring – the silver rim is another indicator of orientation. The silver rim should always be on the side of the lens closest to the patient.


  • “Working distance” (distance of the lens to the patient’s eye) varies by lens. Ensuring the lens is at the right focal length will ensure the finest clarity, depth of focus, and field of view. Refer to your lens’ instruction manual, Volk’s website, or a Volk catalog for listings of working distances.
  • Most lenses are optimized for use at lower slit lamp magnification settings. Increasing the slit lamp magnification may introduce image distortion and aberrations.
    • Suggested slit lamp magnification power for Volk lenses is 6x– 16x, where 10x is the optimal mag. 25x and 40x are too high and will likely cause distortion in the image.