May 2019

REFRACTIVE

Point/Counterpoint
Pearls, pitfalls of small aperture inlay for unhappy pseudophakic patients


by Jay Pepose, MD, PhD, Robert Ang, MD, and Jocelyn Remo, MD

“Advances in ophthalmology are made by insightful, talented surgeons trying new things, and we applaud Dr. Fox and colleagues both for pioneering work and for sharing their experience with the off-label use of the KAMRA inlay in pseudophakes.”

The KAMRA inlay (CorneaGen) is a thin, carbon-impregnated polyvinylidene corneal inlay with a 1.6 mm central aperture and 3.8 mm outer diameter placed in a deep femtosecond-laser assisted corneal stromal pocket to provide extended depth of focus by blocking unfocused peripheral rays of light via small aperture optics. While the inlay is not approved for use in pseudophakes, surgeons can and have used new medical devices off-label when there is good medical rationale and an exercise of sound medical judgment in the best interest of the patient. We are grateful to Drs. Fox, Augustine, and Wiley for sharing their experience with the off-label use of the KAMRA inlay in pseudophakes.
Dr. Fox and colleagues used the KAMRA inlay in two clinical different settings: (1) in patients bilaterally implanted with monofocal IOLs and (2) in patients implanted with multifocal IOLs. In patients with monofocal IOLs, by targeting –0.75 D in the nondominant eye, this shifts the flat defocus curve produced by the KAMRA inlay to the right, expanding through focus with minimal impact on distant vision. This is supported by the findings in Case 3 of Dr. Fox et al.’s article in a patient with pseudophakic mini-monovision, where the UCDVA in the nondominant eye improved from 20/40 to 20/20-2 and the near improved from borderline J3 to J1+ following KAMRA implantation. These findings are very similar to what has been reported when the inlay has been used in phakic patients1 and also when the small aperture is integrated into an IOL2 (IC-8 IOL, AcuFocus), and the patient is targeted for –0.75 D in the small aperture eye. Another advantage of this approach is enhanced stereopsis with the inlay in place compared to in patients with a comparable amount of monovision without the inlay3.
In further support of this concept, a prospective, randomized, clinical trial was conducted of the KAMRA inlay in the nondominant eye of patients undergoing phacoemulsification with bilateral monofocal IOLs. In this trial, the inlay was implanted in the nondominant eye in a premade 200 µm femtosecond laser-assisted corneal pocket immediately after phacoemulsification and implantation of a three-piece Tecnis monofocal IOL (Johnson & Johnson Vision), with the same monofocal IOL also placed in the dominant eye, vs. the same IOL bilaterally implanted in the control group. The manifest refraction in the nondominant inlay implanted eye was –0.39 ± 0.66 D. With 12 weeks of follow-up, investigators found a statistically significant increase in uncorrected intermediate vision in the inlay cohort vs. the control and a two-line enhancement in near vision, although the latter did not reach statistical significance. This improvement in unaided near and intermediate vision was confirmed by a flatter defocus curve in the inlay group, with no statistically significant decrease in binocular contrast sensitivity or visual field testing.4
Drs. Ang and Remo have had similar experience in adding the KAMRA inlay to the nondominant eye of four patients with another monofocal IOL, the Crystalens (Bausch + Lomb), which is labeled as having the equivalent of about 1 D of accommodation. The mean preoperative refraction was +0.125 sphere and –0.50 cylinder. The mean uncorrected distance visual acuity was 20/25 (logMAR 0.1), uncorrected intermediate visual acuity was 20/24 (logMAR 0.1), and near visual acuity was J3 for two patients and J8 and J10 for the other two. The KAMRA was implanted in eyes with prior Crystalens IOL implants under a deep lamellar flap. The mean corneal thickness was 552 µm prior to lamellar flap creation. The mean corneal flap thickness created was 208 µm. At the 1-year follow-up, all patients noted improvement of uncorrected intermediate and near vision, with minimal impact on distance acuity (Tables 1 and 2). There was a modest reduction in monocular but not binocular contrast sensitivity. Results were stable at 4 years of follow-up, and there were no photic complaints.
In addition to their use in patients with monofocal IOLs, Dr. Fox and colleagues present two cases where KAMRA was used in patients with bilateral multifocal IOLs who were dissatisfied with their near vision or complained of photic phenomenon. Generally, the approach to such patients is to methodically correct any residual refractive error, assess the lens capsule and treat even small amounts of PCO, aggressively
treat dry eye, evaluate the macula for conditions that can reduce contrast, and finally allow adequate time for neuroadaptation.
In Cases 2 and 3, Dr. Fox and colleagues took another approach. The residual refractive error was left uncorrected in the dominant eye and a KAMRA inlay was implanted in the nondominant eye, in one case associated with simultaneous PRK with a –0.75 D target and in the other leaving the eye with –0.62 D spherical equivalent. Optically, this combination of a KAMRA small aperture inlay in an eye with a multifocal IOL with the eye targeted for –0.75 D improves near vision but at the cost of decreased uncorrected distant vision. In addition, if the scotopic pupil size is larger than the inlay (which is likely), this would decrease the quality of the distance image. The combination of loss of illumination from the inlay would be compounded with the loss of light to higher diffractive orders with the multifocal IOL, potentially reducing contrast sensitivity. It also does not address photic phenomenon in the dominant eye with the multifocal, which would persist. On the upside, if the patient was disturbed by the outcome of the KAMRA in this setting, the inlay could be easily removed. Perhaps the effect could be (in part) tested preoperatively by a trial of low-concentration pilocarpine drops.
Advances in ophthalmology are made by insightful, talented surgeons trying new things, and we applaud Dr. Fox and colleagues both for pioneering work and for sharing their experience with the off-label use of the KAMRA inlay in pseudophakes. We find the rationale for use in monofocal IOL patients sound and straightforward (with the inlay having been implanted first and the patient undergoing cataract surgery with a monofocal IOL5, 6 targeted at –0.75 D, placing the inlay following monofocal implantation and assuring the end refraction is in this zone, or by implanting an IC-8 with the same target). However, use of the inlay as a primary treatment for dissatisfied patients with multifocal IOLs may have more potential downsides than with a monofocal IOL, and we suggest first treating the residual refractive error (even by a trial of contact lenses or spectacles) and systematically going down the aforementioned checklist of conditions that can reduce contrast sensitivity and increase glare and photic phenomenon before considering a KAMRA inlay in this setting.


Table 1. 1 year postoperative visual acuity (Snellen/logMAR)


Table 2. 1 year postoperative manifest refraction (D)

About the doctors

Jay Pepose, MD, PhD
Director and founder
Pepose Vision Institute
Professor of clinical ophthalmology
Washington University School
of Medicine St. Louis

Robert Ang, MD
Asian Eye Institute
Makati City, Philippines

Jocelyn Remo, MD
Asian Eye Institute
Makati City, Philippines

Contact information

Pepose
: jpepose@peposevision.com
Ang: rtang@asianeyeinstitute.com
Remo: jmremo@asianeyeinstitute.com

References

1. Vukich JA, et al. Evaluation of the small-aperture intracorneal inlay: Three-year results from the cohort of the U.S. Food and Drug Administration clinical trial. J Cataract Refract Surg. 2018;44:541–556.
2. Dick HB, et al. Prospective multicenter trial of a small-aperture intraocular lens in cataract surgery. J Cataract Refract Surg. 2017;43:956–968.
3. Linn SH, et al. Stereoacuity after small aperture corneal inlay implantation. Clin Ophthalmol. 2017;11:233­–235.
4. Elling M, et al. Implantation of a corneal inlay in pseudophakic eyes: A prospective comparative clinical trial. J Refract Surg. 2018;34:746–750.
5. Tan TE, Mehta JS. Cataract surgery following KAMRA presbyopic implant. Clin Ophthalmol. 2013;7:1899–903.
6. Moshirfar M, et al. Cataract surgery in patients with a previous history of KAMRA inlay implantation: A case series. Ophthalmol Ther. 2017;6:207–213

Financial interests

Pepose: AcuFocus, Bausch + Lomb
Ang: AcuFocus, Bausch + Lomb
Remo: None

Pearls, pitfalls of small aperture inlay for unhappy pseudophakic patients Pearls, pitfalls of small aperture inlay for unhappy pseudophakic patients
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