The surgical correction of presbyopia has been an important area of investigation for decades. Both corneal and lenticular methods have been developed with varying degrees of success. Presently, the most promising procedure appears to be corneal inlays. These devices (KAMRA Inlay, Flexivue Microlens, and Raindrop Near Vision Inlay) are implanted in the cornea through a pocket or under a flap in an emmetropic presbyopic patient’s non-dominant eye.
All three inlays have been found to improve near and intermediate vision, but all cause some degree of night glare and distance visual acuity can be affected. An important advantage of the procedure is reversibility.
Here is a summary of the current technologies and the visual results (uncorrected in the operated eye from published papers in the peer-reviewed literature):
KAMRA Inlay from AcuFocus
Principle: Increase depth of field with pinhole effect
Material: Polyvinylidene fluoride
Design: Opaque disc 3.8 mm outer diameter with 1.6 mm central opening, 5 microns thick, and 8400 micro-perforations (5-11 microns in size; allows nutrient flow through the implant)
Results: Improved near vision (mean J1) and intermediate vision (mean 20/25), minimal change in distance vision (mean 20/20).
Availability: 49 countries outside the United States
Flexivue Microlens from Presbia
Principle: Create multifocal cornea by changing corneal power to create slight myopia and monovision
Material: Hydrophilic acrylic
Design: Central plano zone and ring of peripheral refractive power ranging from +1.25 to +3.5D, 3 mm diameter, 15 microns thick, and 0.15 mm central opening (allows nutrient flow through lens)
Results: Improved near vision (mean 20/25), decreased distance vision (mean 20/50).
Availability: CE Mark
Raindrop Near Vision Inlay from ReVision Optics
Principle: Create multifocal cornea by changing corneal shape (central steepening)
Material: Hydrogel (allows direct passage of nutrients through lens)
Design: Clear hyperprolate shaped inlay with no refractive power, 2 mm diameter, 32 microns thick centrally
Results: Improved near vision (mean J1) and intermediate vision (mean 20/25), some decreased distance vision (mean 20/25).
Availability: CE Mark