Two-stage, well-tolerated procedure for inlay ensures refractive stability

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The optimal time of implantation of a corneal inlay (Kamra, AcuFocus) to correct presbyopia in ametropic presbyopic patients seems to be 1 week after traditional LASIK in a planned two-stage KAMRA procedure.

By Lynda Charters;Reviewed by Jeffrey J. Machat, MD, FRCSC

Toronto-The optimal time of implantation of a corneal inlay (Kamra, AcuFocus) to correct presbyopia in ametropic presbyopic patients seems to be 1 week after traditional femtoLASIK in a planned, two-stage Kamra procedure (PLK2), according to Jeffrey J. Machat, MD, FRCSC.

Implantation can be performed in patients who are natural emmetropes-known as pocket emmetrope Kamra-or in patients that have previously had LASIK and now have developed presbyopia-known as post-LASIK Kamra (PLK), said Dr. Machat, chief medical director, Crystal Clear Vision, Toronto.

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For ametropes, patients with significant myopia, hyperopia, or astigmatism, the refractive error must be treated along with the insertion of the inlay. The original treatment combined LASIK and inlay procedure for ametropes, known as cicrular lamellar keratomileusis (CLK), combined 200-µm flap LASIK with the implant and has rapidly become replaced with the inlay pocket procedures, Dr. Machat said.

“We perform LASIK for all ametropic patients creating a 100-µm femtosecond laser flap with our Ziemer Z4 laser, targeting –0.50 to –0.75 D in the non-dominant eye to achieve the optimal results, even those with +0.25 or +0.50 D of hyperopia,” Dr. Machat said.

The challenge was determining when to implant the corneal inlay after LASIK to obtain the best refractive result using the PLK2 or PLK2 procedure, Dr. Machat added.

NEXT: Conquering the challenges

Conquering the challenges

Dr. Machat, who has undergone the inlay procedure himself, explained that the staging of the PLK2 procedure was assessed in a few scenarios, varying the timing between the correction of the refractive error with LASIK, the creation of the pocket, and the insertion of the corneal inlay.

First, the entire procedure was performed in one sitting. The pocket for the inlay was created and immediately followed by LASIK, then it was implanted the same day.

Second, pocket creation and LASIK were performed consecutively, but the inlay implantation was delayed by 1 or 3 days, or 1, 2, or 4 weeks. The concept was to let the eye completely settle, and by only performing the inlay implantation in a quiet eye, hopefully achieve faster visual recovery, he said.

Third, perform traditional femtoLASIK in one session and then pocket creation and inlay implantation from 1 week to 1 month later.

The series of patients only included patients with low-to-moderate refractive errors (–4 to +2 D). Patients with higher refractive errors (<–4 D and >+2 D) were implanted a minimum of 1 month after LASIK to ensure the target refraction was achieved.

NEXT: Understanding the technique

Understanding the technique

The inlay implantation technique involved placing a centration mark on the cornea centered on the visual axis beneath the Takagi microscope, which is coaxial with a coaxial fixation light. The centration marker has a double circle, with an inner 1.6-mm circle and an outer 3.8-mm circular mark.

The inner circle helps the precision of the mark, while the outer circle assists placement. A standard 4-mm marker is 0.2 mm or 200 µm larger than the inlay, and ideal placement is within 300 µm. The AcuTarget HD (AcuFocus) is an instrument that provides preoperative guidance and postoperative confirmation of placement.

NEXT: 'Optimal staging'

‘Optimal staging'

In the 157 patients treated, the uncorrected near visual acuity improved from J6 to J2 at 3 months postoperatively, Dr. Machat noted. The uncorrected distance visual acuity increased from 20/50 to 20/25, and the mean manifest refraction spherical equivalent was 0.64 ± 0.28 D at the same time point.

“Today, our optimal staging is LASIK followed by the pocket (inlay) procedure 1 week later,” Dr. Machat said. “This procedure achieves a LASIK ‘wow’ factor.

“In addition, it better ensures refractive stability, patients have a better appreciation of presbyopia, it is better tolerated by patients with each step taking 6 minutes (and) 1 week apart, and it is better surgically for centration,” Dr. Machat added. “The key benefit is inserting the inlay into a quiet eye.” 

Jeffrey J. Machat, MD, FRCSC

E: sondra.black@crystalclearvision.com

Dr. Machat has no financial interest in any aspect of this report.