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Refractive Inlays

David I. Geffen, OD, FAAO

The latest surgical option for presbyopia, corneal inlay implantation, has been available since 2015 in the United States.¹ Corneal inlays have several advantages over other refractive procedures. The inlays are an additive technology that can be removed in the event of patient dissatisfaction, a complication, or onset of other conditions. These procedures do not remove any tissue, so patients potentially can be candidates for future surgical solutions. Compared to lens surgery, the insertion procedure is less invasive. Depending on the inlay, near correction often remains effective as presbyopia advances.

The 3 styles of corneal inlays, all designed for monocular implantation in the nondominant eye, are corneal reshaping inlays, refractive inlays, and small-aperture inlays. Refractive inlays incorporate power into the inlay, and include the Flexivue Microlens (Presbia) and the Icolens (Neoptics AG). The other inlays are reviewed elsewhere in this text.

FLEXIVUE MICROLENS

Currently in phase III Food and Drug Administration trials in the United States, this hydrophilic acrylic, variable-power inlay has a 3.2-mm diameter, with a 0.015-mm/15-μm edge thickness. The inlay’s central 0.15-mm opening allows for nutrient flow (Figure 6-1).

This inlay has a plano central zone for distance vision and a peripheral zone with increasing rings of higher power for reading vision. Functioning like a multifocal contact lens, the inlay comes in a range of powers. It is inserted under a flap or in a pocket in the nondominant eye, and the surgeon can remove the lens and replace it with a higher power inlay as the patient becomes more presbyopic. The inlay is offered in powers ranging from +1.5 to +3.5 diopters (D), in 0.25-D increments.

A side pocket is created using a femtosecond laser at a depth of 250 μm (Figure 6-2). The inlay is placed using a proprietary inserter (Figure 6-3). Once inserted, the inlay is nearly invisible (Figure 6-4).

Study results found that 12 months after implantation, uncorrected near visual acuity (UNVA) reportedly was 20/32 or better in 75% of operated eyes, whereas the mean uncorrected distance visual acuity (UDVA) of operated eyes decreased from 0.06 ± 0.09 logMAR (20/20), a statistically significant difference.² Overall, higher order aberrations increased, and contrast sensitivity decreased in the operated eye. No tissue alterations were found on corneal confocal microscopy, and no intra- or postoperative complications occurred.² Researchers concluded that the inlay appeared to be an effective method to address the corneal compensation of presbyopia in emmetropic presbyopes between the ages of 45 and 60 years.²

Another study of 81 eyes found the mean UDVA in treated eyes was 0.16 ± 0.08 logMAR after 36 months, which is better than reported monovision outcomes.3 Binocular UDVA of 0.10 logMAR was achieved at 12 months, showing that stereoacuity was maintained after implantation. There was a loss of more than 1 line of UDVA in the treated eye in 62% of the eyes. The study determined no loss of contrast between the treated and untreated eyes.³

Stojanovic et al⁴ investigated the best technique for combining cataract surgery with Flexivue implantation using different combinations of surgical steps: intrastromal pocket creation, inlay implantation, and cataract surgery. Fifteen patients with bilateral cataracts were treated. In Group A (3-step group), the intracorneal pocket was created in the nondominant eye, bilateral cataract surgery was performed 3 months later, and the intracorneal inlay was implanted 6 months after pocket creation. In Group B, bilateral cataract surgery was performed 3 days after pocket creation and inlay implantation in the nondominant eye. In Group C, the pocket creation and the inlay implantation were performed in the nondominant eye 3 months after bilateral cataract surgery.⁴

Twelve months after the inlay implantation, mean monocular UDVA was 20/32 in the 3-step Group A, 20/32 in Group B, and 20/25 in Group C. Achieved mean monocular UNVA was similar in the 3 groups (20/25). No intra- or postoperative complications were observed, and they reported high patient satisfaction and a high spectacle independence rate after cataract surgery.

Beer et al⁵ reported 1-year clinical outcomes following implantation of the inlay. The Flexivue Microlens inlay was implanted in the nondominant eye of patients with a preoperative refraction of -0.5 D to 1.0 D following creation of a 300-μm deep stromal femtosecond pocket. One-year results were reported on 31 patients of mean age 50.7 years. The mean UNVA improved to J1 (Jaeger) in 87.1% of treated eyes and all eyes improved 4 lines. The binocular UDVA was 20/20 in all patients. Ninety percent of the patients reported that their near vision was good or excellent. However, 16.1% lost more than 3 lines of corrected distance visual acuity (CDVA). Anterior segment analysis revealed induction of negative corneal spherical aberration.

Malandrini et al³ reported results of Flexivue Microlens inlay implantation in nondominant eyes using a femtosecond laser. They evaluated a total of 81 eyes. In 26 eyes, the mean preoperative UNVA of 0.76 logMAR improved to 0.10 logMAR 36 months postoperatively. In this same group, the UDVA improved from 0.0 logMAR preoperatively to 0.15 logMAR 36 months postoperatively. However, 16 (62%) of 26 treated eyes lost more than 1 line of UDVA, 5 eyes (19%) lost more than 2 lines of UDVA, and 2 eyes (8%) lost more than 1 line of CDVA at 36 months. The mean binocular UDVA was 0.00 logMAR preoperatively and not significantly different at 36 months postoperatively. The mean spherical aberration increased after surgery and explantation was performed in 6 eyes due to complaints of glare, halos, and reduced UDVA.³

Malandrini et al⁶ also evaluated the biocompatibility of the Flexivue Microlens inlay based on healing of corneal wounds and analysis of corneal structural features using in vivo confocal microscopy and anterior segment optical coherence tomography at 1, 6, and 12 months. In vivo confocal microscopy showed intense cellular activity around the inlay in the stroma, including edema, inflammation, and a degenerative material deposition in the first 12 months. At 1 month, hyperreflective areas beneath the inlay and microfolds were observed in 40% of eyes. The interface reflectivity decreased over time. Six patients had inlay removal postoperatively: 3 prior to 6 months, 3 prior to 12 months. Evaluation of these patients after removal showed clear corneas without signs of irregularity.

ICOLENS

The Icolens inlay is in the earlier stages of development. This inlay is similar to the Flexivue Microlens inlay but incorporates a central power. The inlay is of hydrophilic copolymer, with a 3.0-mm diameter and an edge thickness of less than 15 μm (depending on refraction). For presbyopia, the inlay offers powers ranging from +1.5 D to +3.0 D (in 0.5-D steps). With no power in the center and positive refractive power in the periphery, this inlay’s powers can be exchanged as presbyopia progresses. The device is inserted using a preloaded delivery system. The company has been purchased by Presbia, and the future of this device will most likely be merged with the Flexivue Microlens inlay.

Baily et al⁷ reported results of the Icolens inlay 12 months after implantation in the nondominant eye of 52 emmetropic patients. Mean UNVA in the surgical eye improved from N18/N24 (20/200) preoperatively to N8 (20/50) postoperatively (P < .001). Nine (17%) enjoyed a UNVA of N5 (20/30) or better. Binocularly, there was a mean gain of 0.48 lines of UDVA postoperatively, with 22 patients (42%) gaining more than 1 line. The UDVA in the surgical eye improved from 0.05 logMAR preoperatively to 0.22 logMAR postoperatively, which was statistically significant.

There was a mean loss of 1.67 lines of UDVA (P < .001). The mean loss of CDVA postoperatively was 1.78 ± 1.04 lines (P < .001). No significant change in corneal topography or endothelial cell count was found. Ninety percent of patients reported being happy (“yes” or “rather yes”) with their outcome. However, 11 inlays were explanted due to minimal improvement in UNVA. No significant adverse events were reported during the study.⁷

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