Researchers soon found that, as well as the material, the thickness of the inlay and the depth at which it was implanted were important, as well as permeability and centration.
There was a delay in the general introduction of the treatment while considerable research was done to find safe and reliable combinations of these factors.
[3] By 2020, there are five corneal inlays in use and under development: The KAMRAinlay (AcuFocus, Inc.) is a biocompatible ring that increases the visual depth of field using the physical principle of a small aperture.
[9] The Raindrop Near Vision Inlay, formerly known as the PresbyLens or Vue+ lens (ReVision Optics, Inc) is a thin transparent biocompatible hydrogel implant.
It is implanted under a femtosecond laser flap onto the stromal bed of the cornea, centered over a light-constricted pupil.
The Raindrop Near Vision Inlay reshapes the central region of the cornea to provide a zone of increased power for focusing on near objects.
[12] It was developed by de Diffractive Optics Group (DiOG, Spain) and its working principle combines the pinhole and photon sieve effects.