The natural lens inside the human eye has the ability to adjust focus from distant to near objects, a process known as accommodation. This is accomplished by contraction and relaxation of the ciliary muscle inside the eye. The natural lens becomes thinner or thicker and this allows it to focus at different distances. Unfortunately, humans start losing this ability to change focus in their 40s. This results in difficulty focusing on near objects and in practical terms it translates to difficulty reading small print. The simple solution to this problem is reading glasses, however two new technologies, KAMRA and Raindrop, offer the ability to focus on near objects without glasses.
KAMRA and Raindrop are corneal inlays which are surgically implanted into the cornea. The KAMRA inlay is implanted in the cornea of the non-dominant eye only, and increases its depth of focus. It is a thin opaque ring with a central opening and can be thought of as a contact lens permanently implanted inbetween the layers of the cornea. It is similar to the aperture in a photo camera or a pinhole. As a result, the amount of light entering the eye is reduced, but the depth of focus is increased which results in distant, intermediate, and near objects to all be in focus at the same time. The dominant eye remains unaltered and retains distance vision only. The side effects of the KAMRA inlay may include difficulties with contrast sensitivity, problems with night vision, double vision, ghost images, glare, halos, and color disturbances.
The Raindrop Inlay
The Raindrop inlay is implanted in the cornea and changes the shape of the center of the cornea. This allows for near and intermediate vision. Unlike KAMRA, Raindrop is small disc, about the size of a pinhead. It is made of a clear hydrogel material which is mostly water, and is similar to the material used to manufacture contact lenses. Similarly to KAMRA, Raindrop is implanted into the non-dominant eye only, leaving the dominant eye untouched. The side effects of the Raindrop inlay may include difficulties with contrast sensitivity, problems with the cornea, such as clouding, thinning, scarring, and inflammation, eye infection, and increased eye pressure.