Effect of the Femtosecond Laser on an Intracorneal Inlay for Surgical Compensation of Presbyopia During Cataract Surgery: Scanning Electron Microscope Imaging

Current Eye Research

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Effect of the Femtosecond Laser on an Intracorneal Inlay for Surgical Compensation of Presbyopia during Cataract Surgery: Scanning Electron Microscope Imaging

Marta Ibarz, Jose Luis Rodríguez-Prats, Jose Luis Hernández-Verdejo & Pedro Tañá

To cite this article: Marta Ibarz, Jose Luis Rodríguez-Prats, Jose Luis Hernández-Verdejo & Pedro Tañá (2016): Effect of the Femtosecond Laser on an Intracorneal Inlay for Surgical Compensation of Presbyopia during Cataract Surgery: Scanning Electron Microscope Imaging, Current Eye Research, DOI: 10.3109/02713683.2016.1158273

To link to this article: http://dx.doi.org/10.3109/02713683.2016.1158273

Published online: 03 Jun 2016.

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Download by: [2.139.225.163] Date: 07 June 2016, At: 07:26 CURRENT EYE RESEARCH http://dx.doi.org/10.3109/02713683.2016.1158273

Effect of the Femtosecond Laser on an Intracorneal Inlay for Surgical Compensation of Presbyopia during Cataract Surgery: Scanning Electron Microscope Imaging Marta Ibarza, Jose Luis Rodríguez-Pratsb, Jose Luis Hernández-Verdejoc, and Pedro Tañád aDepartment of Cornea and Refractive Surgery, Oftalvist Juan Bravo Hospital Moncloa, Madrid, Spain; bDepartment of Glaucoma, Oftalvist, Hospital Vistahermosa, Alicante, Spain; cDepartment of Optometry, Universidad Complutense de Madrid, Madrid, Spain; dDepartment of Cataract and Refractive Surgery, Oftalvist, Hospital Vistahermosa, Alicante, Spain

ABSTRACT ARTICLE HISTORY Purpose: To investigate the effect of the femtosecond laser-assisted cataract surgery (FLACS) on porcine Received 18 May 2015 eyes implanted with a Kamra corneal inlay and to describe how the inlay may change the effect of the Revised 9 February 2016 femtosecond laser on the lens. Accepted 21 February 2016 Methods:FLACSwasperformedonsixporcineeyesandaKamra corneal inlay had been implanted, exploring KEYWORDS the lens under the surgical microscope. Another Kamra corneal inlay was attached to the upper part of the Femtosecond laser-assisted transparent hemisphere used for calibration of the femtosecond laser. Capsulorhexis, arcuate incisions, and cataract surgery (FLACS); phacofragmentation were carried out. The Kamra corneal inlay was compared with a nontreated one using a intracorneal inlay; Kamra; scanning electron microscope (SEM), and the hemisphere was analyzed with a surgical microscope. presbyopia; scanning Results: Capsulorhexis and phacofragmentation were completed in all the porcine eyes, although accuracy to electron microscope determine the exact effect on the lens was not possible to achieve. The effect of the femtosecond laser on the PMMA hemisphere through the Kamra corneal inlay showed the capsulorhexis was placed outside the outer margin of the inlay and a sharply sculpted fragmentation pattern with a three-dimensional (donut-shaped) annulus untreated beneath it. SEM images of the nontreated and the treated inlays were comparable. No ultrastructural changes were found in the treated Kamra corneal inlay. Conclusions: FLACS can be performed with a Kamra corneal inlay for surgical compensation of presbyopia without the risk of damaging the inlay. The Kamra corneal inlay acts as a screen that avoids the laser to reach the areas beneath its shadow, but not the exposed areas of the lens.

Introduction solutions. Patients with corneal inlays will develop cataracts and will need surgery in the future, probably demanding the newest With the aging population and change in demographics, presby- technology available for their pathology. At this point, femtose- opia and cataracts have probably become two of the most com- cond laser-assisted cataract surgery (FLACS) has rapidly evolved mon problems the ophthalmologist have to manage daily in the in the past few years, with several clinical studies supporting clinical practice. According to recent estimates, more than 2 improvements in capsulotomy, lens fragmentation, incisions, billion people worldwide are presbyopic,1 and cataract surgery

Downloaded by [2.139.225.163] at 07:26 07 June 2016 macular thickness, and endothelial cell count when compared remains the most commonly performed ophthalmic surgery with – with traditional phacoemulsification.10 14 18 million procedures performed globally every year.2 The World In this study, we examined the effect of FLACS in porcine eyes Health Organization estimates that this number will increase to 32 where a Kamra corneal inlay was previously implanted, and in the million by the year 2020 as the over-65-year population doubles PMMA (poly-methyl methacrylate) hemisphere used for femto- worldwide between 2000 and 2020.3 second platform calibration after the inlay was adhered to the Presbyopia treatment with corneal inlays goes back to upper surface. Macroscopic and microscopic images of the porcine Barraquer, who implanted the first one in 1949.4 Since then, eyes and the PMMA hemisphere, besides scanning electron micro- several designs and materials have been developed,5 and dif- scope (SEM) images from a nontreated Kamra corneal inlay and ferent surgical implantation techniques have been studied.6 another one after the effect of the femtosecond laser, were The Kamra intracorneal inlay (Acufocus, Inc., Irvine, CA, analyzed. USA) utilizes the pinhole effect to increase the depth of focus in the implanted eye, restoring the intermediate and near vision – without a significant impact in the distance visual acuity.7 9 Materials and methods Patients suitable for this technique are 40–65 years old presbyops Porcine study with no cataracts who seek for a reversible solution for their near vision problem. As well as those young LASIK patients operated Six freshly enucleated porcine eyes obtained from animals decades ago have become presbyops and now demand surgical sacrificed for human consumption in authorized facilities for

CONTACT Marta Ibarz [email protected] Department of Cornea and Refractive Surgery, Oftalvist Juan Bravo, Hospital Moncloa, Av. de Valladolid 81, 28008, Madrid, Spain. Color versions of one or more of the figures in the article can be found online at www.tandfonline.com/icey. © 2016 Taylor & Francis 2 M. IBARZ ET AL.

Table 1. Parameters required by the femtosecond laser (Intralase™ FS Laser) to perform the corneal pocket to insert the intracorneal inlay for presbyopia correction. Full lamellar cut Anterior side cut (parameters of the pocket) (parameters of the incision) Pocket 1 Lamellar depth: 200 μm Posterior depth: 230 μm Diameter: 4.0 mm Diameter: 4.7 mm Energy: 1.50 mJ Energy: 2.50 mJ Method: Raster Cut angle: 90° Cut position: 180° Side cut angle: 30° Pocket 2 Lamellar depth: 200 μm Posterior depth: 230 μm Diameter: 6.5 mm Diameter: 7.2 mm Energy: 1.50 mJ Energy: 2.50 mJ Method: Raster Cut angle: 70° Cut position: 180° Side cut angle: 30°

food industry were selected for the in vivo part of the study. The technique chosen to implant the Kamra corneal inlay was the creation of a corneal pocket. The first three eyes received a Figure 1. Kamra inlay attached to the upper part of the PMMA hemisphere with the suction ring ready to be docked in the system. small corneal pocket (Pocket 1) that offered some difficulties to introduce the inlay, so a bigger pocket (Pocket 2) was programmed for the rest of the eyes in order to reduce filled with BSS, docked into the system and treated manipulation and therefore, corneal edema. Depth of the (Figure 1). The intraoperative optical coherence tomogra- dissection plane selected for all cases was 200 μm. phy (OCT) that is integrated in the femtosecond platform Parameters required by the femtosecond laser (Intralase™ FS recognizedtheborderoftheKamracornealinlayasthe Laser, Abbot Medical Optics, Inc., Abbot Park, IL, USA) to pupillary margin. Corrections were needed in order to fit perform the corneal cut are summarized in Table 1. the capsulorhexis outside of the inlay with a 5 mm The Kamra corneal inlay was inserted through the corneal intended diameter. A simulated posterior corneal surface incision into the pocket and centrated in the pupil, so as to and lens had to be designed and introduced in the system leave enough space between the border of the inlay and the data so the treatment could be performed as if it was a real pupillary margin to fit a 5 mm capsulorhexis in all cases. Air eye (Figure 2). Two arcuate incisions in the 180° axis were bubbles accumulated in the interface were extracted by rub- programmed to mark the Kamra corneal inlay (Figure 3). bing gently with a spatula over the epithelium. Corneal This way, we could later distinguish the treated corneal edema in the incision appeared in all cases, but did not inlay from the nontreated one during SEM analysis. interfere with femtosecond laser effect over the lens in any Fragmentation pattern chosen in this part of the study of the eyes. was “quadrants” with a 300 μmgrid(softening).Thetreat- Once the Kamra corneal inlay was correctly placed in the ment was completed successfully, and the glass hemisphere pocket and nicely centrated, the femtosecond laser suction wasanalyzedunderthesurgicalmicroscopetodescribe ring (Catalys® Precision Laser System, Abbot Medical Optics, Downloaded by [2.139.225.163] at 07:26 07 June 2016 Inc.) was fixated and filled with balanced saline solution (BSS® Balanced Salt Solution, Alcon Laboratories, Inc., Fort Worth, TX, USA), and docked into the laser lens. Besides the 5 mm capsulorhexis already mentioned above, the fragmentation pattern selected was “octants” with a 300 μm grid softening. The inlay was extracted from the cornea and the eye was analyzed under the surgical microscope to check for capsulorhexis and fragmentation.

PMMA hemisphere study The femtosecond laser platform used for the study works with a noncontact or fluid-filled interface system. If the Kamra corneal inlay would have been just placed over the PMMA hemisphere and not fixated, when the saline solution was poured, the corneal inlay would have floated. In order to avoid this situation, it had to be attached to the hemisphere surface with glue (Loctite, Henkel Ibérica S.A., Barcelona, Spain) in the four cardinal points right in the edges so as to preserve its structure. Once it was correctly Figure 2. Optical coherence tomography (OCT) of the femtosecond laser plat- placed, fixated, and centrated, the suction ring was applied, form shows modifications required to begin the treatment on the PMMA model. CURRENT EYE RESEARCH 3

Table 2. Order of magnification and description of the scanning electron microscope (SEM) imaging of Kamra 1 (non-treated) and Kamra 2 (treated). Kamra 1 (non-treated) Kamra 2 (femto-treated) 25× General view: arcuate incisions and damage in the borders (manipulation) Caliper: 2 mm 80× General view: inlay margins and General view hole distribution Caliper: 7 mm Caliper: 7 mm 400× General view: arcuate border visible Caliper: 100 μm 2000× Precise image of a hole Arcuate border marks treated Kamra. Precise image of two holes. Hole width from border to Caliper: 20 μm border: 11.5 μm Caliper: 10 μm 4000× Inclined image to see the hole Hole width from border to border: material accumulated in the 10.4 μm margins Caliper: 10 μm Caliper: 10 μm 5000× High-magnification image of High-magnification image of the the surface of the nontreated surface of the nontreated Kamra; Kamra particles of the saline solution used Caliper: 10 μm for the femtolaser treatment can be Figure 3. Display of the Catalys® Precision Laser System platform with the seen planned treatment over the PMMA hemisphere. Caliper: 10 μm

details about the effect of the femtosecond laser on the work distance (ICTS Centro Nacional de Microscopía glass through the Kamra corneal inlay. Electrónica. Data available at www.cnme.es).

Kamra corneal inlay specifications Results Porcine study TheKamracornealinlayusedinthisstudywasthelatest model (ACI 7000PDT). It is made up of polyvinylidene The Kamra corneal inlay could be implanted in the cornea of fluoride (PVDF) and nanoparticles of carbon. The outer the six porcine eyes with no complications. Manipulation of and inner diameters of the inlay are 3.8 and 1.6 mm, respec- the incision needed to introduce the inlay in the pocket was tively, and it is 5 μm thick. In order to allow nutrient flow higher in porcine eyes than in real cases of human patients, through the cornea, but to diminish photic phenomena, probably due to the lower intraocular pressure of animal there are 8400 perforations, 5–11 μm wide, with higher enucleated eyes. Corneal edema appeared in the incision concentration in the center of the annulus than in the per- area but did not interfere with femtosecond laser application iphery and randomly distributed. The microperforations during capsulorhexis and phacofragmentation. Figure 4 shows allow a 5% light transmission rate through the inlay into Downloaded by [2.139.225.163] at 07:26 07 June 2016 the eye (Acufocus, Inc.

Scanning electron microscope imaging Two Kamra corneal inlays were prepared according to the SEM technician indications (metalization with gold) to be analyzed: “Kamra 1,” a nontreated inlay brought directly for us from the supplier with no previous clinical use, and the “Kamra 2,” treated with the Catalys platform over the PMMA hemisphere. Order of magnification and description of the images are summarized in Table 2. The model of SEM utilized for the Kamra analysis was JEOL JSM 6400 placed in the National Centre of Electronic Microscopy (ICTS, Universidad Complutense de Madrid, Madrid, Spain) that works with a thermoionic cathode electron spotlight with tungsten filament. The image resolution with secondary electron detection (25 kV) is 3.5 nm with 8 mm work distance and 10.0 nm with 39 mm work distance. With retrodispersed electron Figure 4. Capsulorhexis and phacofragmentation in the porcine eye with the detection, the image resolution is 10.0 nm with 8 mm Kamra implanted in the corneal pocket. 4 M. IBARZ ET AL.

one of the porcine eyes docked in the femtosecond platform SEM images from the nontreated (Kamra 1) and treated with the Kamra inlay implanted in the cornea, capsulorhexis (Kamra 2) inlays showed in detail the structure of both inlays. being performed around the inlay, and phacofragmentation Further than the arcuate incisions (Figure 6a) of the treated visible inside and around the inlay. Kamra (that allowed to distinguish macroscopically Kamra 1 Once the treatment was completed, each porcine eye was from Kamra 2) and some saline particles accumulated on the analyzed under the surgical microscope. The cornea was surface of Kamra 2 (Figure 6b), we found no more differences extracted to acquire a general view of the lens with the with SEM images up to 5000×. The random distribution of capsulorhexis and fragmentation. We could confirm capsu- the holes appeared to be comparable and the diameters of the lorhexis had been performed in all the eyes, with incomplete holes were pretty much alike ranging from 10 to 11.5 μm cut and adhesions left only in the area beneath the edema of (Figure 6c, d). the corneal incision. Regarding phacofragmentation, the effect of the laser was visible but the accuracy to determine where Effect of the femtosecond laser on an intracorneal inlay and how it had reached the lens was not possible to assess. For for surgical compensation of presbyopia during cataract this reason, we decided to perform the same study in the surgery: Scanning electron microscope imaging PMMA hemisphere used for calibration of the femtosecond platform. Several authors have reported their results with intracorneal inlays for presbyopia treatment. Seyeddain,8 Dexl,9 and Yılmaz15 found the Kamra small-aperture inlay to be safe PMMA hemisphere study and effective for emmetropic presbyopic patients. Tomita16 Femtosecond arcuate incisions, 5 mm capsulorhexis and frag- implanted the inlay in combination with LASIK to treat both mentation, were successfully completed on the PMMA hemi- ametropia and presbyopia, reporting patient satisfaction with sphere. Application of the suction ring with the Kamra fixated their decreased dependence on reading glasses regardless of the preoperative spherical equivalent range. In other study, on the surface and Catalys display image of the treatment μ planification are shown in Figures 1 and 3, respectively. OCT the same author implants the inlay creating a pocket 80 m below a previous LASIK flap, with a reported improvement in of the femtosecond laser platform with the changes required 17 to begin the treatment in the PMMA model are displayed in near vision without significant impact on distance vision. Figure 2. According to these promising results, it is presumable that the Once the treatment had finished, the hemisphere was ana- number of patients receiving this type of implants will lyzed under the surgical microscope to assess where and how increase every year, and many of them will develop cataracts. the femtosecond had reached the PMMA material. Phacoemulsification with a corneal inlay poses some ques- Capsulorhexis was perfectly performed around the outer mar- tions about technical difficulties, biometry, and visual out- μ comes. Surgical technique has already been described by Tan gin of the inlay. Fragmentation (quadrants with 300 m grid 18 softening) was visible and perfectly sculpted inside of the et al. in two clinical cases where a Kamra inlay had been inner margin of the Kamra and outside of the outer border, previously implanted. Besides the need for some ocular rota- but not beneath the inlay. A three-dimensional (donut- tions during capsulorhexis and phacoemulsification to shaped) annulus beneath the Kamra had not been treated improve visualization, no other modifications to their usual and remained intact. Figure 5 shows the treated hemisphere technique were required. According to their results, biometry readings were reliable and the SRK-T formula was accurate Downloaded by [2.139.225.163] at 07:26 07 June 2016 in detail. for intraocular lens power calculation. In our study it was possible to perform the capsulorhexis and fragmentation in porcine eyes and in the PMMA hemisphere used for calibration of the femtosecond platform. Manipulation of the incision needed to introduce the inlay in the pocket in porcine eyes was higher than in our real cases of human patients, probably due to the lower intraocular pressure of animal enucleated eyes. Corneal edema appeared in the incision area of the porcine eyes, but did not interfere with femtosecond laser application during capsulorhexis and phacofragmentation. Corneal edema during FLACS in a patient previously implanted with a Kamra corneal inlay could interfere with femtosecond laser due to corneal opacity. This complication could happen if both procedures (corneal inlay implantation and FLACS) were performed simulta- neously, or if the patient had corneal edema not detected previous to surgery. Microscopical examination of the model allowed us to describe in detail how the femtosecond laser would poten- Figure 5. Capsulorhexis and phacofragmentation are sculpted in the PMMA hemisphere. A three-dimensional annulus beneath the corneal inlay is not tially strike the lens, with a perfectly shaped effect in all the treated and remains clear. exposed areas and an annular zone beneath the corneal inlay CURRENT EYE RESEARCH 5

Figure 6. a: Arcuate incision and random distribution of the holes on the treated Kamra (Kamra 2). b: Saline particles on the surface of the treated Kamra. c: Random distribution of the holes and general structure of the nontreated Kamra (Kamra 1). d: 2000× image of the hole (caliper measures 11.5 μm of diameter in this particular hole).

that remains untreated. We believe that the Kamra corneal degeneration and scar were observed at the location of the inlayactsasa“screen” that prevents the laser to reach the inlay due to the heat and burning. This complication is not lens.Sincecapsulorhexisisoutsideoftheinlay,itisnot expected to occur with FLACS because heat is not delivered affected by this “screen” effect and therefore can be per- to the tissue. In fact, no signs of burning or any other formed as usual. damage to the Kamra corneal inlay could be observed The question about how the femtosecond laser would using SEM imaging. affect the inlay is well documented by the SEM images of To our knowledge, this is the first study to analyze the Downloaded by [2.139.225.163] at 07:26 07 June 2016 the inlay before and after the treatment. The randomized effect of the FLACS in a Kamra corneal inlay for surgical distribution of the holes remains intact, the tissue in compensation of presbyopia during cataract surgery. between them shows no additional damage in the treated However, future studies upon the clinical application of this sample, and no presumed femtosecond impacts can be technique are needed and should be conducted. found in all the surface. Both inlays are comparable, mean- ing that the femtosecond laser can be safely applied in our cataract patients without the risk of damaging the inlay and Acknowledgments with the certainty that capsulorhexis and fragmentation can The authors thank Raquel Aguejas, member of the optometrist team of be performed as in a standard cataract procedure. our clinic, for her ability to manage the femtosecond platform during −15 Femtosecond lasers use ultrashort pulses of light (10 s) the study, and also Juan Gabriel Ortiz, engineer, for his technical that provide very high power in every pulse with low support. energy rates. One single pulse of 100 femtoseconds with a modest energy of 3 mJ (insufficient to raise in a millionth of a Celsius degree the temperature of a water drop) deli- Declaration of interest vers a 30 mW peak power. The pulse transfers the energy The authors report no conflicts of interest. The authors alone are to the focused point with such rapidity that the heat does responsible for the content and writing of the paper. not reach the areas that surround the edge of the treated zone, the effect is called cold ablation.19 Mita et al.20 reported the case of a patient implanted with a Kamra Funding corneal inlay that developed a central serous retinopathy The authors do not have any financial interest in any of the materials or that required photodynamic therapy. One month later, instruments used in this study. 6 M. IBARZ ET AL.

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