Corrective lenses
Our eyes can suffer from all sorts of minor abnormalities: an eyeball that is too long or too short, or diminishing elasticity of the eye muscle, etc. These minor abnormalities cause our vision to be blurry. Corrective lenses correct these abnormalities so that we can see clearly again.
You can also choose a specific feature by adding filters, coatings and other materials to the corrective lenses.