To understand how lenses work, you must first understand a little about the eye. Retina is filled with things that are called rods and cones, and take the light to convert it into electrical impulses that are sent to the brain for processing.
When you get blurry vision, this is due to something called 'refractive errors'. So to fix the mistakes, we use a small plastic lens that corrects them by creating a film that makes contact with the eye. There are many types of contact lenses such as one-day lenses or diurnal lenses (which is also called as dognlinser in Norwegian language).
They help to focus light on the retina and allow the eye to function properly. They work in the same way as glasses work. There are a number of types of errors that lead to different problems and require different recipes for repair.
Myopia or near-sightedness is where distant objects appear blurred while close objects appear clear. It occurs when light entering the eye is not properly focused and is caused by the shape of the eye. It is one of the most common conditions and there are a variety of contact lenses that correct it.
Hyperopia or farsightedness is the opposite, where the items are close are blurry but they are more vivid. Again, this is relatively common and there are many lenses to fix it.
Presbyopia is a condition that is associated with the same ages with hyperopia where near the item to be blurred, but coming from a different cause. While derived from the shape of the eye hyperopia, presbyopia comes from the eye lens hardening with age. To correct the condition, multifocal lenses are often used because they can clean both near and far blurred.