All headlights are made of plastic which deteriorate over time.
Each time you wash the car, apply a plastic protectant to the headlights and tail lights. Spray it on and buff it off. I use this brand.
My car is almost 5 years old and these are the headlights due to always using the protectant after I wash the car.
The Plexus product is not a UV block. Instead, it keeps plastic from deteriorating by keeping the plastic clean, conditioned and polished. The key to success is to start when plastic is new.
Before and after photos were requested which is impossible. This is a guide for prevention which is why this car has not had damaged headlights. This type of product will not work on damaged lights.