Performing Reliable Lens Capsulotomy in the Presence of Corneal Edema with a Femtosecond Laser

Lens Performing Reliable Lens Capsulotomy in the Presence of Corneal Edema With a Femtosecond Laser

Geraint P. Williams,1,2 Benjamin L. George,1 Yoke R. Wong,3 Gary H. F. Yam,1 Marcus Ang,1,2 Shian C. Tay,3–5 and Jodhbir S. Mehta1,2 1Tissue Engineering and Stem Cell Group, Singapore Eye Research Institute, Singapore, Singapore 2Corneal and External Eye Disease Service, Singapore National Eye Centre, Singapore, Singapore 3Biomechanics Laboratory, Singapore General Hospital, Singapore, Singapore 4Department of Hand Surgery, Singapore General Hospital, Singapore, Singapore 5Duke-NUS Medical School, Singapore, Singapore

Correspondence: Jodhbir S. Mehta, PURPOSE. To determine the effects of the Ziemer LDV Z8 liquid interface femtosecond laser Singapore Eye Research Institute, 11 platform during capsulotomy under different energy settings in the presence of corneal Third Hospital Avenue, Singapore edema. 168751; [email protected]. METHODS. Cadaveric porcine eyes (n ¼ 36) employed at less than 6 and greater than 24 post enucleation hours to simulate clear/edematous corneas, underwent capsulotomy with the Submitted: May 15, 2017 Accepted: July 18, 2017 Ziemer LDV Z8 femtosecond laser (5-mm diameter, energy 90%, 130%, or 150%). Lens capsules were removed for evaluation by scanning electron microscopy and rupture strengths Citation: Williams GP, George BL, determined by the single column universal testing system. Following ethical approval, 23 Wong YR, et al. Performing reliable patients had lens capsules removed during routine cataract surgery following manual or Z8 lens capsulotomy in the presence of corneal edema with a femtosecond capsulotomy and subjected to TUNEL assay. laser. Invest Ophthalmol Vis Sci. RESULTS. There was no difference in edge morphology or rupture strength (120, 113, and 118 2017;58:4490–4498. DOI:10.1167/ mN at increasing energy, P ¼ 0.42) in the clear cornea. Only 50% of capsulotomies succeeded iovs.17-22227 at 90% energy in an edematous cornea, improving with increased energy (75% completion at 130%, 100% at 150%). Rupture strength in edematous corneas was not signiﬁcantly different at 112, 133, and 114 mN for 90%, 130%, and 150%, respectively (P ¼ 0.3). In human samples, increased TUNEL-positive cells were seen at 130% energy, but not at 150% (0.0 manual vs. 0.2 [90%] vs. 2.1 [130%] vs. 0.6 [150%], P < 0.05).

CONCLUSIONS. Because of the low energy delivered by a femtosecond nanojoule platform, even incremental increases in energy appeared to have minimal effect on lens capsule morphology and strength and negligible inﬂuence on cell death. Furthermore, increasing energy appeared to enhance consistency and the ability to complete a capsulotomy in an edematous cornea. Keywords: femtosecond laser, corneal edema, energy, capsulotomy

ndothelial dysfunction caused by conditions such as Fuchs’ those with grade 1 disease < 600 lm) may be relatively less E endothelial corneal dystrophy (FECD) and bullous keratop- edematous (thickened), despite frank evidence of decompen- athy result in visual impairment due to corneal edema and sation and yet a greater central corneal thickness (CCT) may be scarring.1–4 When corneal opacification occurs in addition to seen in an optically clear cornea (e.g., greater than 640 lm corneal edema, optimized visualization of the lens capsule by following pre-existing high CCT).11 capsular staining or retroillumination may assist continuous Femtosecond laser-assisted cataract surgery (FLACS) offers a curvlinear capsulorhexis (CCC),5,6 but an endothelial transplant potentially more consistent way of undertaking capsulotomy by is usually indicated at the same sitting. Surgical management of creating a semiautomated anterior lens capsulotomy.12–15 The corneal disease is achieved by selective tissue transplantation effects of a thickened yet transparent cornea on successful by Descemet stripping automated (DSAEK) or Descemet FLACS is unknown. There is potential to use this technology to membrane endothelial keratoplasty (DMEK).7,8 These interven- reduce disruption of endothelial cells by femto-fragmentation. tions are usually undertaken following or combined with This may have a specific role in cases where the endothelium is removal of cataract.7,9 at high risk such as FECD.16,17 Despite these advantages, Cataract surgery may contribute to corneal decompensation femtosecond laser firing patterns are vulnerable to enhance because of endothelial cell damage from phacoemulsification light scatter at deeper dissections, even in optically clear energy, however corneal edema may already be apparent. corneas. Increased variability is seen, for example, in LASIK flap Central corneal thickness increases from healthy individuals creation in the peripheral (thicker) compared with central (558 lm) incrementally from 586 lm in grade 1 FECD to 648 (thinner) cornea.18 This could potentially make femtosecond lm in grade 6 disease.10 However, the precise thickness that tissue cutting more challenging in the presence of corneal predicts the likelihood of decompensation during phacoemul- edema (e.g., penetrating keratoplasty).19,20 As FLACS relies on sification in FECD is ill defined. Relatively thin corneas (such as an optically clear interface, the potential advantage of laser

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TABLE. Summary of Lens Capsule Completion at Different Energy MA, USA), photographed (310 magnification with a Leica microscope; Leica Wetzlar, Germany) and anchored to the Capsulotomy underlying membrane with 10-0 Ethicon overlay sutures. Energy Complete Cut Comment ImageJ 1.38X software (http://imagej.nih.gov/ij/; provided in <6 h 90% 100% (6/6) No complications the public domain by the National Institutes of Health, <6 h 130% 100% (6/6) No complications Bethesda, MD, USA) was used to determine capsule/capsulotomy size by pixilation compared with a reference ruler and <6 h 150% 100% (6/6) No complications 2 24 h 90% 50% (6/12) Failed cuts ( 3), capsule circularity with the formula 4p 3 Area/(perimeter) n ¼ 36 ripped edge (n ¼ 2), (value of 1.0 represented a perfect circle). and significant tag (n ¼ 1) Capsules were washed twice in 13 PBS for 10 minutes each 24 h 130% 75% (n ¼ 8) Failed cuts (n ¼ 1) or ripped before being immersed in a fixative 2% solution of glutaralde- (n ¼ 1) hyde in PBS for 2 hours at room temperature, and then washed 24 h 150% 100% (n ¼ 6) No complications three times with distilled water before incubation in a 1% aqueous solution of osmium tetroxide (FMB, Singapore) for 1 hour at room temperature. Following this, the samples were capsulotomy and fragmentation could hypothetically be dehydrated in increasing concentrations of ethanol (25%, 50%, negated by the inability of the laser to fire successfully through 75%, 95%, and 100% ethanol, with 95% and 100% concentra- a thickened cornea. tions being performed twice). The samples were then critical FLACS capsulotomy may induce capsular tags, leading to point dried using Bal-Tec dryer (Balzers, Liechtenstein) and more serious complications such as anterior capsular tears.21–23 mounted on stubs secured by carbon adhesive tapes. They The strength of the capsulotomy in resisting rupture during were then sputter coated with a 10-nm thick layer of gold (Bal- manipulation of lens material is critical to success.24–29 It has Tec) and examined using a JSM-5600 scanning electron recently been shown that increasing the laser energy pulse microscope (JEOL, Tokyo, Japan). The edges of the extracted may adversely affect the strength of the lens capsulotomy.23 lenticules were then evaluated using scanning electron This effect was noticeable with a high-energy FLACS (‘micro microscopy. The sample processing was performed as de- joule energy’) platform. We have previously shown however scribed previously. For each lens capsule, four micrographs, that in a low-energy high-frequency system (operating in the one in each quadrant, were taken (3140, 3750, and 34000 nanojoule range) that a safe, smooth capsulotomy could be magnification). achieved.30 The utility of such a system in the presence of Lens capsulotomy strength was determined by the single corneal edema is currently unknown, but microjoule energy column universal testing system (3343; Instron Corp., Canton, platforms may penetrate edematous corneas more effectively. MA, USA) after removal of the lens en bloc with nucleus intact High-energy systems have been shown to induce increased or following expression with an ophthalmic viscoelastic device apoptosis of the lens epithelium during femtosecond capsu- (Viscoat, Alcon, Fort Worth, TX, USA). Two mushroom-shaped lotomy, however, suggesting an advantage for manual capsu- pins were placed posterior to the capsulotomy edge and the lotomy including minimal wound healing reaction and lens rate of pin displacement was set at 6 mm/min. Resistance of 31–33 capsule cell death. By contrast, suction trephination the capsulotomy to rupture was measured in meganewtons during penetrating keratoplasty demonstrates less apoptosis and the stretching ratio by (capsulotomy size mm þ displace- 34 than femtosecond laser. The potential for safely increasing ment mm)/capsulotomy size mm, as previously described.30 energy in nanojoule steps to overcome corneal edema has yet to be resolved. Human Capsules The aim of this study was to determine the efficacy of the low-energy Ziemer LDV Z8 liquid interface femtosecond laser Increased cell death at the capsule edge may potentially platform during capsulotomy in the context of corneal edema correlate with a less smooth capsule edge morphology.31 In and at different energy settings to compensate for thickened order to determine cell death at increasing energy during corneas. FLACS capsulotomy, we evaluated lens capsules ex vivo following routine cataract surgery. Human capsules were collected during routine phacoemulsification cataract surgery METHODS (MA, JSM) following informed consent and institutional review board approval in keeping with the tenets of the Declaration of Porcine Capsules Helsinki (CIRB Ref 2015/2565, Singapore). All patients’ corneal Ex vivo cadaveric porcine eyes were sourced from a local thickness were normal, in the range of 520 to 550 lm. Manual abattoir, and capsulotomies performed at less than 6 hours or CCC was achieved with a 27-G needle with Viscoat ophthalmic greater than 24 hours post enucleation and evaluated with the viscoelastic device (Alcon) or capsulotomy with the Ziemer Ziemer LDV Z8 femtosecond laser (software version 35054; LDV Z8 (Ziemer) femtosecond laser (software version 35054) Ziemer, Port, Switzerland) for different laser energies (5-mm for different laser energies (5-mm diameter, 0.8-mm height, cut diameter, 0.8-mm height, cut speed 50 mm/s, energy 90%– speed 50 mm/s, energy 90%–150%), as previously de- 150%), as previously described.30,35 Briefly, due to a tendency scribed.30,35 Mean patient ages (n ¼ 6 for each group) were: to cadaveric porcine corneal epithelium to slough, for manual 69 years (range, 49–75), 90% energy 74 years (56–85), consistency the corneal epithelium was debrided and the 130% energy 71 years (56–76), and 150% 68 years (57–72) (P ¼ globe mounted in a suction stand prior to docking with a liquid 0.62). All cataracts were senile in origin and with no known patient interface followed by suction, liquid immersion, and trauma or coexisting disease. attachment of the laser head. Corneas with impairment of After anterior capsule extraction, all specimens were subjective clarity (i.e., obvious scarring) opacities were immediately fixed in freshly prepared neutral buffered 4% excluded. Forty-four globes were used with n ¼ 6 in each paraformaldehyde in PBS (0.01M; First Base, Singapore) for 1 group for further experimentation (Table). hour at 48C. During fixation, the samples were carefully placed Lens capsules were removed and immediately placed on to with epithelial side facing upward to prevent any mechanical a Millipore millicell culture insert (Merck Millipore, Billerica, damage to cells that might induce unnecessary apoptosis. After

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fixation, the samples were carefully washed with PBS twice (10 mN (84–140) at 130% vs. 118 mN (107–136) at 150% (P ¼ 0.88) minutes each) and subjected to TUNEL assay. (Fig. 2D). The stretch ratio, however, increased with a TUNEL reaction was performed using TMR-In Situ Cell commensurate increase in energy with a stretch ratio of 2.2 Death Detection kit (Roche, Welwyn Garden City, England, (2.0–2.4) at 90% vs. 2.4 (2.2–2.5) at 130% vs. 2.5 (2.4–2.7) at UK), as previously described.31 Briefly, capsule specimens 150% (P < 0.01) (Fig. 2D). were permeabilized with 0.1% Triton X-100 (Sigma-Aldrich Corp., St. Louis, MO, USA) in 0.1% Na citrate (Sigma-Aldrich Energy Effects on Circularity and Strength in Corp.) for 2 minutes on ice, followed by PBS rinses. The Corneal Edema samples were then incubated with 50-lL TUNEL reaction mix for 1 hour at 378C according to manufacturer’s protocol. We retested energy on corneas at 24 hours post enucleation at Positive control was sample pretreated with 5 U/mL DNase I three increasing energy setting—90%, 130%, and 150% (n ¼ 6 (Sigma-Aldrich Corp.) for 20 minutes at room temperature in each group) (Fig. 3A). Circularity remained consistent at (228C) followed by complete TUNEL reaction. Negative different energy settings (Fig. 3A) when capsulotomy was controls were DNase-treated samples without TdT enzyme in achieved (see above comment on capsulotomy formation), TUNEL reaction mix. After incubation, all samples were overall there was no difference between circularity at less than washed three times with PBS and mounted with 40,6- 6 hours and 24 hours (0.99 [0.95–1.0] vs. 0.99 [0.95–0.99]; P ¼ diamidino-2-phenylindole (DAPI)-added fluoromount (Fluo- 0.89). Predictable capsule shrinkage was seen following roshield; Sigma-Aldrich Corp.). Cells along the cutting edge capsulotomy with corneal edema, with a median difference were imaged under fluorescence microscopy (AxioImager Z1; of 0.4 (0.26–0.58), 0.38 (0.24–0.62), and 0.52 (0.35–0.7) mm, Carl Zeiss, Oberkochen, Germany) at a magnification of 310 respectively (Fig. 3B, P ¼ 0.3). (objective). Cells along the cutting edge were positioned in a Scanning electron microscopy images of capsule edge rectangular field of 100 lm in width and quantified for the total following femtocutting in corneal edema are shown at number of cells and TUNEL-positive cells. At least six incremental energy increases (Fig. 3C). No gross difference randomized regions along the cutting edge of each sample in morphology was seen after successful cutting through an were analyzed and cells per millimeter squared and mean edematous cornea at different energies. Furthermore, capsu- percentages of TUNEL cells from different energy settings were lotomy rupture resistance showed no significant difference obtained. across energy settings 112 mN (61–142) at 90% vs. 133 mN TUNEL assays were not evaluated in the porcine model, as (101–153) at 130% vs. 114 mN (100–143) at 150% (P ¼ 0.27) dead tissue would have been expected to demonstrate positive (Fig. 3D). The stretch ratio was also unaltered at increased TUNEL staining irrespective of exposure to capsulorhexis/ energy with a stretch ratio of 2.2 (1.8–2.7) at 90% vs. 2.4 (2.3– FLACS capsulotomy. 2.6) at 130% vs. 2.2 (2.1–2.5) at 150% (P ¼ 0.27) (Fig. 3D). Statistical analysis was performed with the Wilcoxon paired There was no significant difference in strength between test, Kruskal Wallis test with Dunn’s post hoc test with Prism nonedematous and edematous corneas at all energy levels or 5.0 for Macintosh (GraphPad, La Jolla, CA, USA). in stretch ratios at 90% or 130% (P > 0.05), but with a significant difference in stretch ratio seen at 150% energy (2.5 vs. 2.2; P < 0.05). RESULTS Capsulotomy Formation TUNEL Evaluation Positive and negative controls are shown in Figure 4A. This The effects of corneal edema can be seen in Figure 1A. demonstrated that DNase-treated samples as positive control Allowing the cornea to stand for 24 hours post enucleation showed 100% apoptosis; while negative control without TdT resulted in a significant increase in CCT compared with less enzyme had 0%, confirming validity of the assay. Representa- than 6 hours (1035 lm [range, 906–1140] vs. 766 lm [range, tive images from manual cut and LDV Z8 femtosecond cut 651–866]; P < 0.05) (Fig. 1B). Successful capsulotomy was capsulotomies are shown in Figure 4B. Percentage TUNEL- achieved in only 50% (6/12) attempts at 90% energy in an positive cells ( 6 in each group) were 0% (0–0.5) (median, edematous cornea. Representative images showing unsuccess- n ¼ range) in the manual group, 0.2% (0–0.45) at 90% energy, 2.1% ful cuts were illustrated in Figure 1C. This improved however (0.3–4.1) at 130% energy and 0.6% (0–2.5) at 150% energy ( < with increasing energy (75% completion at 130% [6/8 P 0.05). attempts], 100% at 150% [6/6 attempts]). Six-hour cuts were all completed successfully without complication. These data are summarized in the Table. DISCUSSION Energy Effects on Circularity and Strength in a The Ziemer LDV Z8 employs a high repetition femtosecond 15,35,37 Clear Cornea laser at low energy. We have previously evaluated the role of the Ziemer LDV Z8 nanojoule energy platform on lens We tested the effects of energy on corneas at less than 6 hours capsulotomies, which had shown consistency and resistance to post enucleation at three increasing energy setting—90%, rupture with this system.30 Increasing energy in the microjoule 130%, and 150% (n ¼ 6 in each group). Representative images range may adversely affect capsulotomy strength and increase and comparison of the circularity achieved are shown in Figure cell death in high-energy platforms (5–15 lJ),23,31 but smaller 2A. There was a predictable shrinkage of the porcine capsule increase in energy as a means of safely circumventing the with a median difference of 0.56 (0.46–0.59), 0.44 (0.36–0.60), effects of corneal edema with a low-energy laser (<100 nJ or and 0.56 (0.52–0.59) mm, respectively (Fig. 2B, P ¼ 0.42). 0.1 lJ)15 has not been previously determined. Therefore, in Scanning electron microscopy images of capsule edge are this study we found that the consistency of circularity and lens shown at incremental energy increases (Fig. 2C). The elasticity was seen both in clear corneas and at increased laser consistent smoothness of the edge was reflected in the energy—from a conventional recommended setting of 90% to strength of the capsules when subjected to resistance with 150%. These observations were similar to our previous no significant difference in 117 mN (109–133) at 90% vs. 116 experimentation with porcine and human lens capsulotomies

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FIGURE 1. Capsule retrieval, time to completion, and circularity. Color photographs with accompanying optical coherence tomography images showing the corneal clarity and thickness at less than 6 hours and greater than 24 hours post enucleation (A). Note the clear cornea seen in the left photograph and the presence of edema on the right. Thickness measurements are compared in (B)(n ¼ 12; *P < 0.05). Representative photographs of lens capsules, which failed to cut in the presence of corneal edema, are shown in (C). These represent abnormal tearing of the capsule secondary to incomplete cutting. The left images shows a partially cut capsulotomy in situ, the middle panel shows the same capsule following removal with an extended crescent of lens capsule, and the right image shows an irregular, square edge.

at 5-mm diameter at 90% energy.30 However, in the presence of energy settings, despite edema. We have previously shown corneal edema, a successful lens capsulotomy was only similar smooth capsulotomy edge morphology with the LDV achieved at increased energy settings (150%). The lower Z8 using nanojoule energy, however, there has been shown to energy setting resulted in 50% failure in edematous corneas be signiﬁcant variation in the appearance among microjoule including irregular or incomplete cuts, which could lead to energy laser platforms, especially when increasing the energy anterior capsular tears.21–23 This represents a potential settings from 5 to 15 lJ. These changes include serrations and challenge for patients who may have corneal edema associated morphologic changes including coagulation of collagen with FECD undergoing FLACS. ﬁbers.31,37 Although increasing energy within one of the The laser focus is anatomically more posterior to facilitate microjoule energy laser platforms (e.g., LenSx) showed capsulotomy and successful cuts demonstrated that the edges increased disruption to capsule edge morphology, considerable of the capsulotomy appeared smooth and consistent across variation exists in other platforms (e.g., Catalys, Victus)

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FIGURE 2. The effects of energy alterations on capsulotomy circularity, edge, and strength in a nonedematous cornea. Representative images at increasing energy at less than 6 hours post enucleation with circularity (A). Predicted and actual capsule sizes are shown in (B). Scanning electron microscopy images of capsule edge taken at increasing energy are shown in (C). Lenses were removed with nucleus intact and resistance of the capsulotomy to rupture was measured in millinewtons and the stretching ratio by (size mm þ displacement mm)/size. Two mushroom-shaped pins were placed posterior to the capsulotomy edge and the rate of pin displacement was set at 6 mm/min. Comparison between strength and stretch ratio at different energies are shown in (D). *P < 0.05. **P < 0.01.

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FIGURE 3. The effects of energy alterations on capsulotomy circularity, edge, and strength in a edematous cornea. Representative images at increasing energy at greater than 24 hours post enucleation with circularity (A). Predicted and actual capsule sizes are shown in (B). Scanning electron microscopy images of capsule edge taken at increasing energy are shown in (C). Lenses were removed with nucleus intact and resistance of the capsulotomy to rupture was measured in millinewtons and the stretching ratio by (size mm þ displacement mm)/size. Two mushroom-shaped pins were placed posterior to the capsulotomy edge and the rate of pin displacement was set at 6 mm/min. Comparison between strength and stretch ratio at different energies are shown in (D). NS, not signiﬁcant. *P < 0.05. **P < 0.01.

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FIGURE 4. Human lens capsule TUNEL staining following femtosecond capsulotomy. Positive controls pretreated with DNase and TdT enzyme and negative controls without TdT enzyme are shown in (A). Representative ﬂuorescence microscopy images (310) from manual cut and LDV Z8 femtosecond cut capsulotomies at 90%, 130%, and 150% are shown in (B). Percentage TUNEL-positive cells (taken from 6 randomized regions along the cutting edge of each sample in a rectangular 100-lm ﬁeld) are shown in (C). *P < 0.05.

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reflecting incrementally larger differences in energy deliv- We have demonstrated that the LDV Z8 femtosecond laser ery.21,23,31,38,39 We did not see this with the nanojoule energy was able to create a consistent, circular, and smooth laser used in clear, nonthickened, or edematous corneas in this capsulotomy that was capable of resisting stress at increased study. energy. Because of the low energy delivered by the Ziemer Z8 It is likely that the magnitude of the energy increase with a platform, even the incremental increases in energy appeared to nanojoule energy platform (90% vs. 130% vs. 150%) does not have minimal effect on lens capsule morphology and strength induce collagen melting and denaturation seen at higher and negligible influence on cell death. In eyes with FECD and 23 energy settings with a microjoule energy platform. Unlike early decompensation, there are potential benefits of under- 23 previous studies evaluating increasing microjoule energy, we taking FLACS, and thereby reducing endothelial damage from saw no significant difference in the strength of the capsulot- phacoemulsification energy.41,42 Increasing energy in the omy at increasing energy in the nanojoule range (90% vs. 130% nanojoule range appears to enhance consistency in the ability vs. 150%). This was unaffected by the presence or absence of to complete a capsulotomy in an edematous cornea, which corneal edema and consistent with the edge morphology may be useful when performing FLACS in eyes with concurrent demonstrated. This suggests that the 150% setting has corneal pathology such as FECD. We therefore advocate that incrementally lower energy than for platforms operating in 15 greater energy should be used in an edematous cornea for the microjoule range. We cannot explain why the stretch FLACS-assisted capsulotomy. ratio increased at 150% energy as intuitively as we might have expected this to reduce. The elastic recoil seen in the capsulotomy was consistent with our previous data and the Acknowledgments 40 behavior of porcine lenses. It would suggest that this was Supported by a National Medical Research Council, Translational & unaffected with the LDV Z8 laser and despite the personal Clinical Research (TCR) Flagship Programme, Singapore Grant observation of a temporary whitening of the capsulotomy edge (NMRC/TCR/R1020-SERI/2013). Geraint P. Williams’ SERI fellow- at higher (150%) energy setting in patients (MA) compared ship is supported by a Dowager Eleanor Peel Trust Travelling Grant with 90% energy. and a Royal College of Ophthalmologists/Pfizer Ophthalmic TUNEL staining demonstrated low apoptosis across energy Fellowship. settings. DNase-treated positive controls showed 100% apo- Disclosure: G.P. Williams, Ziemer (R); B.L. George, None; Y.R. ptosis; while negative control without TdT enzyme had 0%. Wong, None; G.H.F. Yam, None; M. Ang, None; S.C. Tay, none; This validated the assay and is important when considering J.S. Mehta, Ziemer (C) energy disruption to the capsule itself, which was low, albeit at a statistically higher level in the 130% setting. It is unclear why this peaked at this energy level but it is possible that removal of References the lens capsules may have been more traumatic in these capsules. At less than 2% TUNEL-positive cells however we 1. Borboli S, Colby K. Mechanisms of disease: Fuchs’ endothelial postulate that this appeared to be clinically insignificant. Mayer dystrophy. Ophthalmol Clin North Am. 2002;15:17–25. et al.31 previouslyshowedthatbycontrasttherewere 2. Terry MA, Ousley PJ. 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Relationship of believe this will be different on the anterior capsule.34 All other Fuchs endothelial corneal dystrophy severity to central data however point to a consistent, smooth, and strong capsule corneal thickness. Arch Ophthalmol. 2012;130:433–439. edge in a clear or edematous cornea in our porcine model. 11. Repp DJ, Hodge DO, Baratz KH, McLaren JW, Patel SV. Fuchs’ Furthermore, energy effects of a femtosecond laser platform in endothelial corneal dystrophy: subjective grading versus an edematous cornea have not previously been explored in any objective grading based on the central-to-peripheral thickness model. ratio. Ophthalmology. 2013;120:687–694.

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