Surface coatings improve your vision quality and lenses durability. Hard coating enables plastic lenses to endure scratches better. Antireflection coating decreases the glare of the glass surface and reflections that tire the eyes. It also adds to the light strength of the spectacle lenses i.e. eyes get a clearer image of the object. The smudge-resistant surface helps to keep the lenses clean as soil and smudges do not leave traces so easily so you see more clearly.