Corneal Inlays for Presbyopia Correction
Corneal Inlays for Presbyopia Correction
Some corneal inlays are designed to change the eye's refractive index. Similar to some multifocal contact lens or IOL designs, these microlenses provide distance vision through a plano central zone that is surrounded by one or more rings of varying add power for near vision. They are intended for implantation in the nondominant eye.
The Flexivue Microlens (Presbia, Los Angeles, California, USA), based on a precursor known as the InVue lens, is a transparent, 3.0-mm diameter hydrogel implant containing an ultraviolet blocker. It has a 0.15 mm opening in the center to facilitate fluid and nutrient flow. This is surrounded by a plano central zone and a refractive peripheral zone with add power from +1.25 to +3.5 D, in 0.25-D steps. The lens thickness varies between 15 and 20 μm depending on add power. It is intended for implantation in a corneal pocket at a depth of 280–300 μm.
The Presbia Flexivue is currently in Food and Drug Administration clinical trials. Although this lens is commercially available in a number of countries outside the USA and the company says that more than 500 have been implanted, the published literature is limited. With the current design, there is one case report in the literature of a 56-year-old emmetrope, whose uncorrected near visual acuity (UCNVA) improved from 20/50 to 20/20 at the first postoperative week.
A prospective study of 47 presbyopic emmetropes implanted in the nondominant eye with the Flexivue Microlens in a femtosecond laser-created corneal pocket found that uncorrected near visual acuity (UCNVA) was 20/32 or better in 75% of implanted eyes at 12 months (mean 20/25). Mean uncorrected distance visual acuity (UCDVA) decreased three lines, from 20/20 to 20/50, although binocular UCDVA was not statistically affected. Thirty-seven percent of patients lost one line of best-corrected distance visual acuity (BCDVA) in the operated eye, but no patient lost two lines. There was a statistically significant decrease in mesopic and photopic contrast sensitivity at a number of spatial frequencies and an increase in higher-order aberrations (HOAs) in the implanted eyes. Overall patient satisfaction and spectacle independence was high, but 12.5% of patients experienced halos and glare at 1 year postoperatively.
These results are not as good as those reported in a prospective study of 45 emmetropes implanted with the earlier version of the inlay (InVue lens) inserted in a corneal pocket created with a microkeratome. One year after surgery, 98% of those patients had UCNVA of 20/32 or better in the operated eye. UCDVA was 20/40 or better in 93% of implanted eyes. Three patients lost one line of BCDVA in the operated eyes.
Several studies at professional meetings have shown positive results in small cohorts. Surgeons have also anecdotally reported successfully recentering, exchanging, and explanting this device, supporting the idea that it is easily removable.
The Icolens (Neoptics AG, Hunenberg, Switzerland), is based on a similar design to the Flexivue inlay. There have been promising early reports at professional meetings from clinical trials underway in Europe, but no details have yet been published in the peer-reviewed literature. The Icolens is currently under consideration for a US investigational device exemption in anticipation of embarking upon a clinical trial.
Refractive Optic Inlays
Some corneal inlays are designed to change the eye's refractive index. Similar to some multifocal contact lens or IOL designs, these microlenses provide distance vision through a plano central zone that is surrounded by one or more rings of varying add power for near vision. They are intended for implantation in the nondominant eye.
Flexivue Microlens
The Flexivue Microlens (Presbia, Los Angeles, California, USA), based on a precursor known as the InVue lens, is a transparent, 3.0-mm diameter hydrogel implant containing an ultraviolet blocker. It has a 0.15 mm opening in the center to facilitate fluid and nutrient flow. This is surrounded by a plano central zone and a refractive peripheral zone with add power from +1.25 to +3.5 D, in 0.25-D steps. The lens thickness varies between 15 and 20 μm depending on add power. It is intended for implantation in a corneal pocket at a depth of 280–300 μm.
The Presbia Flexivue is currently in Food and Drug Administration clinical trials. Although this lens is commercially available in a number of countries outside the USA and the company says that more than 500 have been implanted, the published literature is limited. With the current design, there is one case report in the literature of a 56-year-old emmetrope, whose uncorrected near visual acuity (UCNVA) improved from 20/50 to 20/20 at the first postoperative week.
A prospective study of 47 presbyopic emmetropes implanted in the nondominant eye with the Flexivue Microlens in a femtosecond laser-created corneal pocket found that uncorrected near visual acuity (UCNVA) was 20/32 or better in 75% of implanted eyes at 12 months (mean 20/25). Mean uncorrected distance visual acuity (UCDVA) decreased three lines, from 20/20 to 20/50, although binocular UCDVA was not statistically affected. Thirty-seven percent of patients lost one line of best-corrected distance visual acuity (BCDVA) in the operated eye, but no patient lost two lines. There was a statistically significant decrease in mesopic and photopic contrast sensitivity at a number of spatial frequencies and an increase in higher-order aberrations (HOAs) in the implanted eyes. Overall patient satisfaction and spectacle independence was high, but 12.5% of patients experienced halos and glare at 1 year postoperatively.
These results are not as good as those reported in a prospective study of 45 emmetropes implanted with the earlier version of the inlay (InVue lens) inserted in a corneal pocket created with a microkeratome. One year after surgery, 98% of those patients had UCNVA of 20/32 or better in the operated eye. UCDVA was 20/40 or better in 93% of implanted eyes. Three patients lost one line of BCDVA in the operated eyes.
Several studies at professional meetings have shown positive results in small cohorts. Surgeons have also anecdotally reported successfully recentering, exchanging, and explanting this device, supporting the idea that it is easily removable.
Icolens
The Icolens (Neoptics AG, Hunenberg, Switzerland), is based on a similar design to the Flexivue inlay. There have been promising early reports at professional meetings from clinical trials underway in Europe, but no details have yet been published in the peer-reviewed literature. The Icolens is currently under consideration for a US investigational device exemption in anticipation of embarking upon a clinical trial.
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