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Good results reported from US trial on corneal inlay in presbyopes
A surgeon reports on his center's use of the Raindrop inlay and his implantation technique.
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The “wow” effect occurs when your cataract or refractive surgery patient realizes how much better his or her vision is as a result of the surgery you performed. We all like that moment and hope that we can achieve it every time. But when it comes to presbyopes, the wow effect is not quite as easy to achieve, particularly here in the United States, where our treatment options are limited to less than a handful of products.
I think this is changing, though. We are one of the U.S. centers that enrolled patients as part of the U.S. Food and Drug Administration phase 3 clinical study of the Raindrop corneal inlay (ReVision Optics) for treatment of presbyopia in emmetropes, and the results, to date, indicate that this inlay may help us to deliver more wow moments.
The Raindrop is a hydrogel corneal inlay that is implanted in the nondominant eye under a corneal flap created by a femtosecond laser (one-third of the central corneal thickness depth). It is designed to create a profocal cornea by gently steepening the central cornea, creating a smooth gradient of power. The U.S. investigational device exemption study is a prospective, multicenter nonrandomized clinical trial with close to 400 patients enrolled; who will be followed for 36 months postoperatively. Surgery is performed on the nondominant eye only, and patients must be emmetropes with no greater refractive error than 0.5 D of myopia to 1 D of hyperopia. The primary outcome of the study is improvement in near visual acuity, with a requirement that at least 75% of patients achieve uncorrected near visual acuity of 20/40 or better, both monocular and binocular. We are also looking at intermediate and distance visual acuity results, as well as patient satisfaction. To date, we have implanted 87 inlays at our center.
Jeffrey Whitman
Results to date
The 6-month results that we reported at this year’s American Society of Cataract and Refractive Surgery meeting on the first patients who reached the 6-month visit demonstrated the impact that the Raindrop can have on a presbyope’s vision. Preoperatively, the average uncorrected near visual acuity was 20/80 monocular and 20/50 binocular. At 6 months postoperatively, the mean uncorrected near visual acuity was 20/20 (J1+), both monocularly and binocularly (Figure 1). As important, near vision improved immediately after surgery; at the 1-week visit, the mean uncorrected near visual acuity improved to 20/25 and the binocular vision was slightly better (Figure 1).
The profocal cornea created by the Raindrop provides consistent near improvement. Looking at the number of lines of near vision gained over time, at 1 week, patients gain on average 4.5 lines; in subsequent follow-ups, the average gain increases, with 5.7 lines of monocular near improvement at the 6-month visit. Binocular near vision showed a similar trend, with an average gain of four lines at 1 week that improved to 4.7 lines at 6 months.
With some presbyopic treatments, there can be a trade-off with a significant loss of distance vision in exchange for improved near vision. However, our experience with the Raindrop shows that this is not the case. At 6 months, 86% of the patients had uncorrected binocular visual acuity of 20/20 or better at all distances (far, intermediate and near), with 98% achieving 20/25 or better across the whole range of vision tested. The visual acuities remained stable over the 6-month follow-up period (Figure 2).
In my practice, no patients have lost two or more lines of best corrected distance or near visual acuity. There has been one explantation due to excessive fibrosis (the patient returned to preoperative visual status within 4 weeks), while three patients had to have inlays replaced due to displacement or flap striae. Three patients developed haze over the implant, which resolved with a second round of steroid treatment.
Patient-reported visual symptoms were infrequent and never worse than mild. Overall satisfaction in our patients at 6 months was 93%, with 63% indicating that they were completely satisfied and 21% stating that they were very satisfied. None were dissatisfied.
Ease of use
In addition to the visual outcomes, one of the other features of the Raindrop that we like is the ease of implantation. There is no requirement of special centration equipment, and it is straightforward to implant the device. As indicated, we implant the inlay under a femtosecond flap with a depth of one-third of the central corneal thickness. This is the flap thickness that the manufacturer has determined provides the best nutrition flow through the cornea, decreasing the possibility of a significant inflammatory response.
To implant the inlay, you create the flap, lift it and lay it back, without “taco-ing” it. It is important to remember to keep the stromal side of the flap moist and clean because the flap will be open for a longer period of time than for a standard LASIK case.
The inlay is preloaded in a disposable delivery device. Once the bed is prepped and dry, you lay the delivery device flat on the stromal bed over the light-constricted pupil and then use a second instrument (I use a Sinskey hook) on top of the inlay. Then, you pull the inlay delivery device away, leaving the inlay in the center of the pupil. At this stage, it is easy to gently push or pull the inlay with the Sinskey hook to ensure that it is well-centered over the pupil. However, the inlay is resistant to mild decentration and it will work well even if it is slightly inferior, superior, temporal or nasal.
The next step is to allow the inlay to dry out and adhere to the stromal bed. Through the microscope, you will see the fluid in the inlay start to be pulled out into the stromal bed. As it does this, the inlay will start to dimple. Once it is uniformly dimpled, then it is time to replace the flap. To do this, moisten the stromal side of the flap again with balanced salt solution. You should also carefully wet the gutter of the corneal bed, taking care not to wet the central bed area or the inlay, and then lay the flap back into place.
Because of the inlay, the standard steps that you would do next after LASIK do not apply. Instead, irrigate around the edge of the flap, pushing away from the hinge. This technique works well, without disturbing the inlay. Once you are satisfied with the position of the flap, take the patient to the slit lamp to check on the position of the inlay. This is done by blocking the nonoperative eye and asking the patient to look straight ahead into the light while using a perpendicular slit lamp beam to gauge the position.
Trade-offs and other uses
In our practice, we currently use the two multifocal IOLs that are available in the U.S., the Tecnis (Abbott Medical Optics) and the AcrySof ReSTOR (Alcon), as well as the accommodating Crystalens AO (Bausch + Lomb). There is also the option of giving the patient monovision.
With monovision, the patient loses accurate distance vision in the near eye. Approximately 60% of patients will be able to accept this trade-off. We are all aware of the trade-offs with multifocal IOLs, including a loss in contrast sensitivity. The same can be said for other corneal inlays on the market outside the U.S. that use a pinhole effect to create near vision. By reducing the light that enters the eye, there is a loss of contrast sensitivity, particularly at night. We do not see this problem with the Raindrop. The same is true with presbyLASIK and the visual trade-offs that can happen with this technique, and compared with presbyLASIK, the inlay is removable.
While presbyopes are the primary target for this inlay, once approved in the U.S., I think it will also be an excellent solution for pseudophakic patients with monofocal IOLs. We will be able to give this patient population profocal vision with a simple flap and the addition of this inlay at the time of the treatment. I also foresee that this implant will continue to work as these presbyopes age because the Raindrop should be able to stay in place when the time comes to have cataract surgery; it does not block the view of the visual axis, and because it has no refractive power and is ultra-thin, it does not affect axial length readings. Not only will this reduce the cost of cataract surgery, managing a patient with a corneal inlay is much less labor intensive than those implanted with a presbyopic IOL; there will be less chair time with a higher degree of patient satisfaction.
Of all the technologies that I have worked with in 20 years of practice, this inlay is probably the most people-pleasing thing that I have done. The technology is easy to work with, patients adapt to it well and there is no worry about any strange postoperative problems — you just center it and it works. If the patient or physician is unhappy with the results, just lift the flap, remove the inlay and the eye rapidly returns to preoperative vision parameters.