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Near vision can be optimized with scleral micro-inserts
Excimer laser enhancements can be performed to improve results in eyes with residual refractive error after scleral micro-insert surgery for presbyopia correction.
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Finding a solution to presbyopia, a condition that affects nearly 90 million Americans and 1.7 billion people worldwide, has long been the holy grail in ophthalmology. Most of our current surgical approaches to presbyopia, including monovision LASIK and multifocal IOLs, provide improved near vision but at the cost of some compromise to distance acuity or quality.
I have been involved as an investigator in the clinical trial of the VisAbility micro-insert system (Refocus Group). In this procedure, four tiny PMMA inserts, each about the size of a grain of rice (Figure 1), are implanted in the sclera, outside the visual axis. The micro-inserts are designed to be placed bilaterally. Although the mechanism of action is not entirely clear, it is believed the micro-inserts increase tension on the zonules to partially restore accommodation. As a scleral procedure, the scleral micro-insert procedure is less invasive than an intraocular procedure; it preserves both the cornea and the lens and can be reversed by removing the inserts.
John Meyer
I now have 5 years of personal experience with these scleral micro-inserts, and they have been implanted internationally for nearly 15 years. What my patients really love is the seamless range of vision, from far to near. In other words, there is no gap in intermediate vision or angling to find the “sweet spot” for different distances. We have found the best results are obtained in patients with plano refraction. However, for eyes outside of plano, physician initiated post-study treatments suggest that laser vision correction before or after the procedure can help to fine-tune the results.
The procedure
To insert the VisAbility device, the surgeon first recesses the conjunctiva at the corneal limbus. Guided by a small docking station, a spring-loaded sclerotome is docked to the station and precisely creates four lamellar scleral tunnels at the oblique quadrants of the eye 4 mm from the limbus. The docking station stabilizes the eye and standardizes the width, depth and orientation of the tunnels created by the sclerotome. Once each tunnel is created, the micro-insert is placed in the tunnel. After all four quadrants are complete, the conjunctiva is reapproximated. I typically place a punctal plug at the time of the procedure because aggressive management of the ocular surface is important for success with this procedure, as with other refractive procedures.
Complete results from a phase 3 pivotal clinical trial of 360 patients between the ages of 45 and 60 years, treated at 13 U.S. clinical sites, are currently being prepared for submission to the FDA, but early results from selected sites suggest patients can achieve up to a four-line improvement in near visual acuity. In a previous confirmatory study, 90.3% of patients reported that their near vision was better or significantly better since the procedure and 95% could see J3 or better at 12 months. I have found that vision stabilizes at about 2 to 3 months, with some additional modest improvement at 6 to 12 months, and then remains quite stable over time. The procedure has not been associated with glare, halos or dysphotopsia.
Laser vision correction enhancement
After the conclusion of the previous confirmatory clinical trial, some emmetropes and low hyperopes had become more hyperopic with age. The decrease in accommodative amplitude meant they could continue to see well at distance, but their near vision was less satisfactory. Thirty-one of these patients (62 eyes), with a mean manifest refraction spherical equivalent (MRSE) of +0.56 D and mean uncorrected distance visual acuity (UCDVA) of 20/26.8 at baseline, elected to undergo a laser vision correction enhancement. These enhancements were not part of the current U.S. investigational device exemption study patient base. All had undergone the VisAbility procedure at least 2 years prior and were treated at one of five U.S. sites.
While some surgeons were able to perform LASIK (see sidebar), all of my enhancement patients underwent wavefront-optimized PRK procedures. Because the micro-inserts are well outside the excimer laser treatment zone, they do not impede the PRK procedure.
Six months after enhancement, mean UCDVA had improved to 20/20 and mean MRSE was nearly plano, at –0.03 D. Among a consistent cohort of 22 eyes for which data were available at 1 month, 3 months and 6 months, there was a mean improvement in near visual acuity of more than two lines compared with their post-VisAbility baseline (Figure 2). Follow-up is ongoing.
Among those I have personally enhanced, all are spectacle-independent and seem to be the most highly satisfied of any group of scleral micro-insert patients I have treated. In the future, if a two-step procedure is desired, I think it would be ideal to wait at least 3 to 6 months after the micro-insert procedure before performing laser vision correction.
Scleral implants in post-LASIK patients
I have also treated a small group of five patients (10 eyes) in Jamaica who had successful LASIK in the past to correct +2 D to –4 D of refractive error. These enhancements were also not part of the current U.S. IDE study patient base. All of these patients had undergone LASIK at least 1 year prior, with their original treatments performed between 1996 and 2013, and had subsequently become presbyopic. We all have patients such as these in our practices, and they are among the most motivated to undergo presbyopia-correcting surgery because they have enjoyed the benefits of spectacle independence for years already.
Among the 10 eyes treated, the post-LASIK MRSE ranged from –0.5 D to +0.5 D (mean –0.05 D). Six months after the scleral micro-insert procedure, there was a mean gain of 3.6 lines of near visual acuity at 40 cm, using the Sloan ETDRS chart (Figure 3).
In conclusion, scleral micro-inserts are a promising procedure for the correction of presbyopia. Given that most presbyopes are not plano, early data suggesting we can enhance the procedure with laser vision correction or perform the procedure on those who may have undergone laser vision correction earlier in life are encouraging. - By John Meyer, MD
For more information:
John Meyer, MD, can be reached at The Eye Care Institute, 1536 Story Ave., Louisville, KY 40206; email: mailto:jmeyer@eyecareinstitute.com.
Disclosure: Meyer reports he is a clinical investigator for Refocus Group.
LASIK after scleral micro-inserts
by David Schanzlin, MD
If enhancement is needed after scleral micro-insert surgery, my preference is to perform LASIK because of the rapid visual recovery compared with PRK. Thus far, I have enhanced 10 patients, with LASIK in about half those eyes and PRK in the rest.
David Schanzlin
LASIK can be performed if the surgeon can successfully fit the femtosecond laser suction ring on the eye and position it to create a well-centered flap. The biggest barrier to creating a LASIK flap with the scleral micro-inserts in place was achieving good flap centration. With the docking station instrumentation, I was able to achieve a precise placement of the scleral micro-inserts, which should make LASIK enhancement easier in the future.
Further study of LASIK after scleral micro-inserts is certainly needed. However, given that all of our refractive surgery procedures occasionally require an enhancement, the ability to enhance this presbyopia-correcting procedure is encouraging.
For more information:
David Schanzlin, MD, can be reached at Gordon Schanzlin New Vision Institute, 8910 University Center Lane, Suite 800, San Diego, CA 92122; email: dschanz123@aol.com.
Disclosure: Schanzlin reports he is chief medical officer for Refocus Group and is compensated for his efforts with consulting fees, equity and grant support.