Without seeing anything we really can’t tell you what needs work but a few basic suggestions:
-Make sure you are using the refractive glass material
-Make sure the lenses you’ve modeled actually consist of multiple elements that are similar to an actual camera lens, most of the depth found on a camera lens happens as the light bends through the many elements.
-Make sure your ray bounces are cranked up, it will take a lot of bounces + CPU time to get light from the outside world inside. Also make sure you’ve checked the global illumination and caustic boxes in the settings.
-Make sure you are using an environment that has something to reflect. Studio environments won’t have much to reflect, so the reflections in your lens will be lifeless and boring. If you are trying to render the outside of a lens and need studio quality lighting, use two different passes with two different lighting environments to get reflections on the lens.
Give all that a shot then post what you’re actually trying to achieve.