A soft contact lens.
Made of various kinds of plastic, contact lenses come in a number of varieties, including hard and soft (although soft is by far more common now), and disposable and extended-wear. The specific dioptre needed to treat the patient's condition can be prescribed by an optometrist and provided by an oculist[?].
Tinted contacts, which may or may not be prescription but are tinted to change the colour of the iris, are used for cosmetic reasons.