A sterile implantable device inserted into the natural cornea to treat presbyopia [age-related hyperopia (far sightedness)] based on aperture reduction. It is typically made of plastic material and is shaped as a thin annulus (disc) formed to fit the curvature of the cornea; it includes a central opening that restricts the optical aperture of the eye to increase depth of field. It is intended for long-term implantation and is surgically inserted in an intrastromal pocket or flap made by a keratome or an appropriate laser.