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Intraindividual comparison between femtosecond laser–assisted and conventional cataract surgery
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ARTICLE
Intraindividual comparison between femtosecond laser–assisted and conventional cataract surgery Anna S. Mursch-Edlmayr, MD, Matthias Bolz, MD, Nikolaus Luft, MD, Michael Ring, PhD, Thomas Kreutzer, MD, Christoph Ortner, MD, Matthias Rohleder, MD, Siegfried G. Priglinger, MD
Purpose: To compare the safety and efficacy between femtosecond laser–assisted cataract surgery using the Victus laser system and conventional cataract surgery.
postoperative complications and the effective phacoemulsification time (EPT). Intraocular lens and capsulotomy centration were evaluated using retroillumination slitlamp photography.
Setting: Department of Ophthalmology, Kepler University Hospital, Linz, Austria.
Results: The study enrolled 50 patients. No intraoperative complications occurred in either group. The ECD, CCT, and central retinal thickness were similar between the groups at all follow-up examinations (P > .05). The EPT was not statistically significantly different between the groups (P Z .22). The IOL centration was similar between the groups (P Z .93).
Design: Prospective randomized case series. Methods: Both eyes of patients with age-related cataract were randomized to conventional cataract surgery or femtosecond laser– assisted cataract surgery, both with intraocular lens (IOL) implantation. Postoperative follow-up was at 1 day, 1 week, 1 month, 3 months, and 6 months and comprised corrected distance visual acuity, endothelial cell density (ECD), central corneal thickness (CCT), and central retinal thickness. The main outcomes were intraoperative and
C
ataract extraction is the most frequent ophthalmic surgery.1 Manual creation of a capsulorhexis, which in general is considered the most difficult surgical step, requires individual surgical skills and experience. In addition, excessive transmission of energy during phacoemulsification can cause complications such as capsule tears or corneal endothelium damage.2 Hence, the femtosecond laser was introduced for use in various steps of cataract surgery to increase perioperative safety and precision. Today, 5 femtosecond laser systems for assisting cataract surgery are commercially available.3 Although the systems have many large similarities, they differ in the implemented anterior-segment imaging and in the patient-interface systems.4 The Victus platform (Technolas Perfect Vision GmbH) is the only system with integrated swept-source optical coherence tomography (SS-OCT) imaging, which shows greater sensitivity and a lower signal-to-noise ratio
Conclusion: Femtosecond laser–assisted and conventional cataract surgery using the mentioned system were equally safe and effective. J Cataract Refract Surg 2017; 43:215–222 Q 2017 ASCRS and ESCRS
than the current spectral-domain OCT (SD-OCT) systems.5 In addition, this laser is the only system that uses a dual modality interface. For capsulotomies and lens fragmentations it uses soft docking, for which less applanation (and thus lower vacuum) is needed. Hard docking requires full corneal applanation with higher vacuum, which is necessary for alignment of corneal incisions.6 To our knowledge, the present study is the first to investigate the Victus system in femtosecond laser–assisted cataract surgery using a prospective intraindividual control design. The aim of this study was to evaluate the safety and efficacy of the laser platform in femtosecond laser–assisted cataract surgery versus conventional cataract surgery. PATIENTS AND METHODS This prospective randomized intraindividual comparison study included patients with bilateral age-related cataract who were
Submitted: June 14, 2016 | Final revision submitted: November 21, 2016 | Accepted: November 26, 2016 From the Department of Ophthalmology and the Ars Ophthalmica Study Center (Mursch-Edlmayr, Bolz, Luft, Ring, Ortner, Rohleder, Priglinger), Kepler University Hospital, Linz, Austria; the Department of Ophthalmology (Luft, Kreutzer, Priglinger), Ludwig-Maximilians University, Munich, Germany. Drs. Mursch-Edlmayr and Bolz contributed equally to this work. Supported by a grant from Technolas Perfect Vision GmbH. Corresponding author: Matthias Bolz, MD, Department of Ophthalmology, Kepler University Hospital, Krankenhausstraße 9, 4020 Linz, Austria. E-mail: matthias.bolz@ akh.linz.at. Q 2017 ASCRS and ESCRS Published by Elsevier Inc.
0886-3350/$ - see frontmatter http://dx.doi.org/10.1016/j.jcrs.2016.11.046
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scheduled for cataract surgery in both eyes. The study protocol was reviewed and approved by the local ethics committee and followed the guidelines set forth in the Declaration of Helsinki. Inclusion criteria were a minimum age of 18 years and agerelated cataract. Exclusion criteria were small pupils (!6.0 mm with therapeutic mydriasis) and manifest glaucoma treated with antiglaucoma drugs. One eye of each patient had cataract surgery with conventional phacoemulsification (referred to as conventional cataract surgery), whereas the other eye had femtosecond laser–assisted cataract surgery (referred to as femtosecond cataract surgery). Allocation of the eyes to the respective procedure group was by balanced block randomization using Excel software (Microsoft Corp.).
The Oertli OS3 system (Oertli Instrumente AG) was used for phacoemulsification in both groups. The average phaco power and the equivalent effective phaco time (EPT) were monitored. A Tecnis ZCB00 intraocular lens (IOL) (Abbott Medical Optics, Inc.) was implanted in the capsular bag in both groups to guarantee comparability between each eye and surgical technique. The refractive power of the IOL was calculated with an IOLMaster biometer (Carl Zeiss Meditec AG), which uses the principle of partial coherence interferometry to measure the axial length of the globe. The postoperative therapy regimen was consistent between the 2 groups. It comprised 3 mg/mL tobramycin–1 mg/mL dexamethasone (Tobradex) 6 times daily for 1 week and 0.9 mg/mL bromfenac (Yellox) twice a day for 4 weeks.
Femtosecond Laser The Victus femtosecond platform uses a 1028 nm wavelength diode-pumped solid-state laser that has a 2-piece curved patient interface, including a disposable suction ring clip with a thin liquid layer as a docking interface. Intraoperative imaging is provided by real-time SS-OCT. The maximum possible pulse frequency is 160 kHz, the pulse duration varies between 290 femtoseconds (fs) and 550 fs, and the pulse energy ranges from 0.5 to 10 mJ. By docking the laser assembly, pressure sensors monitor the pressure between the docking device and the eye to allow the surgeon to adjust the positioning. Lens fragmentation options include ring cuts, radial cuts, and a combination of sectorial and quadrant cuts.3 Laser settings followed the manufacturer's specifications and were set according to the cataract degree graded using the nucleus staging system of the Pentacam Scheimpflug imaging device (Oculus Optikger€ate GmbH) (Table 1).
Preoperative and Postoperative Assessments All examiners at the postoperative follow-up visits were blinded to the randomization of the patient. Preoperative assessments comprised corrected distance visual acuity (CDVA) measurement using standard Early Treatment Diabetic Retinopathy Study charts, slitlamp examination including indirect fundoscopy, and measurement of intraocular pressure using Goldmann applanation tonometry. Corneal topography and pachymetry were assessed with a Pentacam Scheimpflug-based topography system. Cataract degree was evaluated using the lens density assessment function with blue-light illumination available in the Scheimpflug system software. The Scheimpflug device nucleus staging classifies the opacity of the lens in 5 stages.7 Endothelial cell density was measured using a dedicated endothelial microscope (EndothelMikroskop EM-2, bon Optic Vertriebsgesellschaft mbH). Central retinal thickness was assessed using SD-OCT (Spectralis, Heidelberg Engineering GmbH). Postoperative assessments comprised CDVA testing, comprehensive slitlamp OCT, and Scheimpflug imaging examinations at 1 day, 1 week, 4 weeks, 3 months, and 6 months. Furthermore, the degree of anterior chamber inflammation (cells and flare) was evaluated at the slitlamp (BC 900, Haag-Streit AG), and the results were recorded using standardized uveitis nomenclature.8 Adverse events were recorded during surgery and at each followup. Individual pain level during surgery was assessed 1 day after each operation using a dedicated patient questionnaire. After femtosecond laser–assisted cataract surgery, patients were asked to define their pain level during the laser procedure on a scale from 1 (no pain) to 5 (intense pain). All patients were asked about their pain level in general during the cataract surgery. After surgery in the second eye, patients were asked to compare the pain level between the 2 types of surgery and which procedure they would recommend.
Surgical Technique Five surgeons (S.P., M.B., C.O., R.S., T.K.) performed the procedures, and the same surgeon operated on both eyes of an individual patient. All surgeons involved in the study had performed at least 1000 conventional cataract surgery procedures. Capsulorhexis creation and lens fragmentation using the phacochop technique were performed manually in the conventional cataract surgery group. The femtosecond laser was used for anterior capsulotomy and lens fragmentation in the femtosecondassisted group. A constant capsulotomy size of 5.0 mm in diameter was maintained by the laser system in the femtosecond group. Capsulotomies were automatically centered on the pupil by the onboard software. After the laser procedure, patients were transferred to the phacoemulsification system. Corneal incisions were created, and the anterior capsule was removed with a forceps.
Table 1. Laser settings of the femtosecond laser for capsulorhexis and lens fragmentation, according to Scheimpflug nucleus staging. Scheimpflug Nucleus Staging Step/Setting
0
1
2
3
4
Diameter (mm)
5200
5200
5200
5200
5200
Energy/pulse (nJ)
7000
7000
7000
7000
7000
7000
7000
7000
7500
8000
4
4
4
8
8
7000
7000
7000
7000
7000
5
3
2
0
0
3000
2500
2000
0
0
Capsulorhexis
Lens fragmentation Energy/pulse (nJ) Number of radial cuts Diameter of radial cuts (mm) Number of circular cuts Diameter of circular cuts (mm)
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Comparison of the Capsulotomies and Intraocular Lens Centration At the third follow-up 3 months after surgery, slitlamp photographs were taken to evaluate the centration of the capsulorhexis and the IOL in vivo. The photographs were analyzed by 2 investigators. An ellipse was fitted to the manually defined points of the pupil to calculate the center of the pupil (Figure 1, red cross). Circles were fitted to determine the center of the capsulotomy (Figure 1, blue cross) and the center of the IOL (Figure 1, green cross). Centers were assessed on the basis of x–y coordinates. The IOL centration (DRIP) corresponds to the Euclidian distance between the 2 marks of the center of the IOL and the pupil (equation 1 and Figure 1). The DRIC represents the distance between the center of the capsulotomy and the IOL (equation 2). The DRCP represents the centration of the capsulotomy in reference to the pupil and is calculated by equation 3. rffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi 2 2 DRIP Z (1) xPupil xIOL þ yPupil yIOL rffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi 2 2 DRIC Z xIOL xCapsulotomy þ yIOL yCapsulotomy DRCP Z
rffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi 2ffi 2 xPupil xCapsulotomy þ yPupil yCapsulotomy
parametric data. Paired samples were analyzed using Friedman testing or analysis of variance according to their parametric distribution. Frequencies of nominal scaled variables (postoperative subconjunctival hemorrhage, Descemet folds) were analyzed using the chi-square test. The learning curve for each surgeon (represented by the reduction in EPT) was tested by calculating the Spearman rank correlation coefficient. The level for statistical significance was set at a P value of less than 0.05.
RESULTS The study included 50 patients. The mean age of the 31 women and 19 men was 72 G 6 years. Three patients (6 eyes) were lost to follow-up. The full range of nucleus staging criteria (minimum 0, maximum 4) was covered in both groups (Figure 2). The mean time between surgery in the 2 eyes of each patient was 9.1 G 9 days. Safety
All surgery with the implantation of the IOL was successfully completed in both groups. Haptics were successfully implanted in the capsular bag in all eyes, and no eye required sutures. In the femtosecond group, suction loss followed by redocking of the laser occurred twice (2 patients [4.3%]) and additional epinephrine (Suprarenin) was injected intracamerally during surgery in 7 eyes because of reflective miosis. Three eyes in the conventional cataract surgery group were treated with epinephrine. The difference between the groups was not significant (P Z .31). A remaining bridge of tissue connecting the dissected disk with the anterior capsular bag was observed in 5 eyes (10.6%) in the femtosecond group. The tissue had to be manually disrupted in these cases before it could be removed. No other intraoperative complications, such as capsule rupture or nucleus drop, occurred in either group.
Intraoperative Complications
(2)
(3)
The primary endpoint concerning efficacy was the EPT, which represents the time to emulsify and extract the opaque lens when working at 100% phacoemulsification energy. Furthermore, each surgeon’s experience in femtosecond laser–assisted cataract surgery was correlated with the EPT to determine the learning curve. Capsulotomies of the 2 groups were compared according to the centration of the capsulorhexis and the IOL. A secondary endpoint was the comparison of the individual patient’s perception of both types of surgery. Statistical Analysis Statistical analysis was performed using SPSS software (version 23.0, PASW/SPSS, International Business Machine Corp.). Sample-size calculation was performed based on previously published data for EPT in femtosecond laser–assisted cataract surgery and conventional cataract surgery with a statistical power of 80%.9 Descriptive values are given as the mean G SD. Data were tested for normal distribution using the Kolmogorov-Smirnoff test and qualitatively checked with a Q–Q plot. Means were compared using the Mann-Whitney U test for unpaired nonparametric data and the Student t test for unpaired
Postoperative Complications On the
first day after surgery, a subconjunctival hemorrhage was present in 27 eyes (57.5%) in the femtosecond group and in 1 eye (2.1%) in the conventional group; the difference was statistically significant (P ! .05). Descemet folds were observed in 13 eyes (27.7%) after femtosecond laser–assisted cataract surgery and in 9 eyes (19.1%) after conventional cataract surgery, with no statistically significant difference between the
Figure 1. Left: Diagram of calculation of the IOL centration. The red circle marks the pupil, and the green circle indicates the IOL. Right: Retroillumination slitlamp photograph with marked borders of the pupil (red line), intraocular lens (green line), and capsulotomy (blue line). Crosses mark the centers. The blue cross denotes the center of the capsulotomy (DRIP Z distance between center of pupil [red cross] and the center of the intraocular lens [green cross].
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Intraocular Lens Centration and Capsulotomy Overlap
There was no significant difference in IOL centration with reference to the pupil between the groups. Intraocular lens centration with reference to the capsulotomy was similar between the groups (Table 4). Centration of the capsulotomy with reference to the pupil was better in the femtosecond group than in the conventional group (P ! .05) (Table 4). Patients’ Perceptions
Figure 2. Comparison of the complete intervention time between surgical techniques.
groups (P Z .33). No significant differences in postsurgical inflammation (eg, intracameral cell count 1 day 1 after surgery) were found between groups (P Z .22). One eye in the femtosecond group had a choroidal effusion 1 day after surgery. Restoration to the original condition was achieved by the use of oral prednisolone (75 mg) for 5 days. Influence on Corneal and Retinal Variables
Table 2 shows the analyzed corneal and retinal parameters as well as the P values for the comparisons between the femtosecond group and conventional group. Endothelial cell density, central corneal thickness (CCT), and central retinal thickness were comparable between the groups before surgery and at all follow-ups. Efficacy
The EPT was significantly correlated with the nucleus staging in both groups (femtosecond: r Z 0.3, P Z .03; conventional cataract surgery: r Z 0.5, P ! .01). Although there were no significant differences in the EPT between groups, the complete intervention time was significantly longer in the femtosecond group than in the conventional group (Table 3 and Figure 2). Learning Curve
Nineteen femtosecond laser–assisted cataract surgery procedures were performed by surgeon 1, 9 by surgeons 2 and 3 each, 8 by surgeon 4, and 2 by surgeon 5. The EPT was not statistically significantly reduced with increasing surgical experience in the femtosecond group (no significant correlation for surgeon 1 to 4). For surgeon 5, the sample size did not permit statistical analysis of the learning curve. The results were the same for the duration of the laser procedure, defined as the time between docking and removing the laser system, as well as for the complete surgery time. Visual Acuity and Refraction
Visual acuity was significantly improved beginning 1 day postoperatively in both groups (P ! .01). There was no significant difference in CDVA between the 2 groups at any follow-up. Volume 43 Issue 2 February 2017
Regarding the patients’ response to the questionnaire, the mean pain during the laser procedure was 1.6 G 0.82. The mean during cataract extraction after laser treatment was 1.4 G 0.61. The mean pain during cataract surgery was 1.34 G 0.63 in the conventional group. No significant difference between the groups was found (P Z .26). Thirty patients (63.8%) reported that they had more pain during femtosecond laser–assisted cataract surgery than during conventional cataract surgery. Twenty-seven patients (57.4%) said they would recommend conventional cataract surgery over femtosecond-assisted surgery. DISCUSSION The aim of this study was to evaluate the safety and effectiveness of the Victus femtosecond laser system for cataract surgery. There were no statistically significant differences in EPT, CDVA, ECD, CCT, or central retinal thickness between femtosecond laser–assisted cataract surgery and conventional cataract surgery. The only difference was in capsulotomy centration. To our knowledge, this is the first prospective randomized intraindividual study using this laser system. It focused on safety, evaluated by analyzing surgical or postoperative complications, and on effectiveness, determined by refraction, visual acuity, and capsulorhexis and IOL centration. Regarding safety, no severe intraoperative complications occurred in either group. Femtosecond laser–assisted capsulotomy was incomplete in 10.6% of these eyes. Results regarding capsule tags vary in the literature2,10–13 (Table 5). For the Victus system, incomplete capsulotomy rates between 3.6% and 8.8% have been reported.2,13 As indicated by Roberts et al.,12 the docking process is essential for successful and complete capsulotomies in femtosecond laser–assisted cataract surgery. The relatively high level of suction breaks in the present study compared with rates in the recent literature might be indicative of possible docking issues. There is evidence that corneal folds during the laser procedure resulting from incorrect docking can cause incomplete capsulotomies in femtosecond laser–assisted cataract surgery.14 Hence, the relatively high percentage of capsule tags in our study might be a result of the learning curve.12 In our study, no eye had an anterior capsule tear or IOL dislocation, which is in accordance with the low rates reported in the recent literature2,10–13 (Table 5). The only statistically significant difference between the femtosecond group and conventional group after surgery was the number of patients with a subconjunctival hemorrhage, with a higher incidence in the femtosecond group. This was most likely caused by the vacuum of the docking
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FEMTOSECOND LASER–ASSISTED VS CONVENTIONAL CATARACT SURGERY
Table 2. Between-group comparison of CDVA, ECD, CCT, and central retinal thickness over time. After Surgery Parameter/Group
Before Surgery
1 Day
1 Month
3 Months
6 Months
Mean CDVA (decimal) Femtosecond
0.67 G 0.30
1.10 G 0.28
1.20 G 0.18
1.20 G 0.27
1.20 G 0.23
Conventional
0.70 G 0.3
1.00 G 0.24
1.20 G 0.21
1.20 G 0.24
1.20 G 0.24
.71
.48
.58
.17
.95
Femtosecond
2438.7
2480.8
2165.4
2156.1
2389.1
Conventional
2435.0
2418.9
2165.3
2136.3
2357.6
.82
.17
.64
.7
.75
Femtosecond
d
48.00 G 188.0
128.80 G 403.0
68.60 G 258.4
39.40 G 298.3
Conventional
d
5.70 G 212.5
124.64 G 285.0
97.70 G 323.5
76.80 G 338.6
P value
d
0.26
0.65
0.86
0.57
P value 2
Mean ECD (cells/mm )
P value Mean DECD (cells/mm ) 2
Mean CCT (mm) Femtosecond
551.0
572.3
546.3
553.0
551.6
Conventional
552.1
574.4
536.2
552.8
551.0
.8
.92
.97
.94
.94
Femtosecond
d
19.96 G 95.0
5.31 G 50.7
0.90 G 10.2
0.60 G 10.4
Conventional
d
22.38 G 95.5
16.10 G 70.3
0.70 G 11.3
1.10 G 9.1
P value
d
.88
.7
P value Mean DCCT (mm)
.95
.91
Mean CRT (mm) Femtosecond
285.73 G 29
281.09 G 29
299.60 G 51
292.30 G 33
290.50 G 29
Conventional
285.50 G 25
279.70 G 26
298.40 G 58
290.10 G 29
288.90 G 28
P value
.93
.84
.55
.94
.69
Mean DCRT (mm) Femtosecond
d
3.36 G 10
8.27 G 17
8.59 G 45
5.43 G 10
Conventional
d
3.64 G 6
7.65 G 29
9.09 G 38
5.56 G 8
P value
d
.19
.99
.37
.93
Means G SD D Z differences between initial values and the follow-up values; CCT Z central corneal thickness; CDVA Z corrected distance visual acuity; CRT Z central retinal thickness; ECD Z endothelial cell density
interface.6 The Victus laser uses a contact interface with soft docking for the capsulotomies, which means less vacuum is applied. With the Lensar system (Lensar, Inc.), subconjunctival hemorrhage after femtosecond laser–assisted cataract surgery was reported in 43.8% of patients.15 The Lensar uses a noncontact applanation system, which is known to cause less subconjunctival bleeding.3,14 Thus, based on our rate of approximately 58%, we conclude that soft docking leads to slightly more subconjunctival bleeding than a noncontact system. One eye had a choroidal effusion after femtosecond laser– assisted cataract surgery, which receded after the use of oral
steroids. This complication had not been previously described in the literature.16 We hypothesize that the choroidal effusion was caused by the vacuum during docking of the laser. In our study, there was no statistically significant change in ECD or CCT and no difference between the groups during the 6-month follow-up. In contrast to our finding, another study17 found that corneal endothelial cell loss and corneal thickness were statistically significantly lower after femtosecond laser–assisted cataract surgery than after conventional phacoemulsification, as was the EPT. However, the EPT was similar in both groups in our study, which in part could explain the difference in findings. Volume 43 Issue 2 February 2017
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Table 3. Between-group comparison of EPT, maximum phaco power, and complete intervention time.
Parameter/ Group
Mean ± SD Femtosecond Group
Parameter
Conventional Group
Table 4. Between-group comparison of the centration parameters evaluated by retroilluminated slitlamp photographs.
P Value*
Mean ± SD (mm)
DRIP
2.51 G 1.7
2.82 G 1.6
.22
Femtosecond
Max phaco power (%)
60.10 G 5.94
61.28 G 4.0
.51
Conventional
Intervention time (min)
16.6 G 4.4
10.21 G 2.8
!.01
EPT (s)
0.22 G 0.13 0.23 G 0.13
DRIC
EPT Z effective phacoemulsification time *Mann-Whitney U test
Femtosecond
0.2 G 0.12
Conventional
0.19 G 0.13
DRCP
An early study of femtosecond laser–assisted cataract surgery18 showed that intraoperative complications decreased with the number of surgeries performed, indicating that this new technique has a learning curve. Furthermore, increasing surgical experience was shown to decrease the need for ultrasound (US) energy for phacoemulsification; in a study of surgeons who had performed 1400 femtosecond laser–assisted cataract surgery procedures,19 there was no US exposure in 97% of 100 eyes. A recent study20 challenges these findings by showing a plateau of reduction in EPT after performing 99 femtosecond laser–assisted cataract surgery procedures. We could not prove a learning curve in the current study, which could also be because of the small number of patients and thus the small sample per surgeon. Regarding effectiveness, femtosecond laser assistance did not statistically significantly reduce the EPT or mean phaco energy. Similar and diverse results have been reported.3 In a metaanalysis,16 the EPT was statistically significantly lower in femtosecond laser–assisted cataract surgery; however, laser system variability was not taken into account. In another study,2 the EPT and mean phaco energy were statistically significantly lower in the femtosecond group (56 surgeries with Victus laser) than in the conventional group (63 surgeries). On the other hand, no statistically significant differences in EPT were found between 38 eyes having femtosecond laser– assisted cataract surgery using the Lensx laser system (Alcon)
Femtosecond
0.19 G 0.11
Conventional
0.24 G 0.13
Mean Diff (mm)
P Value*
0.003
.93
0.005
.65
0.54
.049
DRCP Z distance between the center of the capsulotomy and of the pupil; DRIC Z distance between the center of the capsulotomy and of the intraocular lens; DRIP Z distance between the center of the pupil and the center of the intraocular lens *Mann-Whitney U test
and 38 eyes having conventional cataract surgery.21 These contradictory findings could be because different laser systems and settings as well as phacoemulsification techniques were used. In our study, the EPT in the conventional group was very low because the surgeons used the stop-and-chop technique only and not the divide-and-conquer technique. In the present study, the surgery time was statistically significantly longer in the femtosecond group than in the conventional group. Femtosecond laser–assisted cataract surgery is known to be more time consuming because patients are initially positioned under the laser and then moved to the surgical table.22 Hence, logistics seem to be relevant to the flow of the daily clinical routine.6 Regarding lens and capsulotomy centration, results in some studies6,18,23 indicate that femtosecond laser–assisted capsulotomies are more consistent in their precision and that they result in better IOL centration. For example, in a study by Kranitz et al.24 IOLs implanted after femtosecond-assisted cataract surgery had better centration than those implanted after conventional cataract surgery. However, in our study IOL centration in relation to the
Table 5. Studies of intraoperative complications of femtosecond laser–assisted cataract surgery. Percentage Study*/Year Bali 201211 (n Z 200)
Suction Breaks
Anterior Capsule Tags
Anterior Capsule Tears
Lens Dislocation
2.5
10.5
4
2
10.5
2
2
12
(n Z 200)
2.5
12
(n Z 1300)
0.61
1.62
0
0
NA
3.6
1.8
1.8
Roberts 2013 Roberts 2013
Reddy 2013 (n Z 56) 2
10
(n Z 1852)
NA
1.62
1.84
0
13
(n Z 1105)
0.45
8.8
0.81
0
4.3
10.6
0
0
Abell 2015
Chee 2015
Current 2017 (n Z 47) NA Z not available *First author
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capsulotomy and to the pupil was similar between the groups. In addition, level of significance was borderline for better centration of the capsulotomy aperture with femtosecond surgery compared with conventional surgery. In addition to safety and effectiveness, patient feedback was evaluated in detail using a standardized questionnaire. The results showed that femtosecond laser–assisted cataract surgery did not offer advantages in terms of the patients’ level of postsurgical satisfaction. The patients’ perception of the 2 surgical procedures was similar. A shortcoming of this study was that 5 surgeons performed the operations in a rather small patient cohort, which could bias the outcomes. Hence, analysis of the learning curve was limited by the small number of femtosecond laser–assisted cataract surgery procedures per surgeon. In addition, surgeons were highly experienced in conventional cataract surgery but not in femtosecond laser–assisted cataract surgery, which might bias the comparison of some outcome parameters (eg, EPT). However, we believe our results are representative of those in a clinical routine at a center where cataract surgery is mainly performed conventionally. Even so, this was the first randomized intraindividual study on the Victus femtosecond laser system and its comparability to other laser systems still has to be clarified in a large-scale study. In conclusion, femtosecond laser–assisted cataract surgery with the Victus femtosecond laser platform showed a good safety profile. Nevertheless, patients who had this procedure had a notably high rate of capsule tags and subconjunctival hemorrhages. No statistically significant reduction in the EPT compared with the EPT for conventional cataract surgery was found. Centration of the capsulotomy was statistically significantly better in the femtosecond laser–assisted cataract surgery group. Patients’ satisfaction was not higher with the femtosecond procedure. All in all, femtosecond laser–assisted cataract surgery based with the Victus system was safe and effective with results similar to those of conventional surgery. WHAT WAS KNOWN Excessive transmission of energy during phacoemulsification in cataract surgery can cause complications, such as damage to the corneal epithelium or capsule tears. Femtosecond laser–assisted cataract surgery has the potential to reduce the phaco energy by softening the lens before US phacoemulsification. Still, results in the literature vary.
WHAT THIS PAPER ADDS The EPT was similar between femtosecond laser–assisted cataract surgery and conventional cataract surgery. The femtosecond laser platform used in the study showed a good safety profile perioperatively as well as during 6 months of follow-up. With femtosecond laser–assisted cataract surgery, a 10% rate of anterior capsule tag was observed. On the first day after femtosecond laser–assisted cataract surgery, approximately 58% of the eyes had a subconjunctival hemorrhage. After having femtosecond laser–assisted cataract surgery in 1 eye and conventional cataract surgery in the fellow eye, more than 50% of the patients said they would recommend the conventional procedure.
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REFERENCES 1. Urh BW. History of ophthalmology at Baylor University Medical Center. Proc (Bayl Univ Med Cent) 2003; 16:435–438. Available at: https://www.ncbi.nlm. nih.gov/pmc/articles/PMC1214563/pdf/bumc0016-0435.pdf. Accessed December 24, 2016 2. Reddy KP, Kandulla J, Auffarth GU. Effectiveness and safety of femtosecond laser–assisted lens fragmentation and anterior capsulotomy versus the manual technique in cataract surgery. J Cataract Refract Surg 2013; 39:1297–1306 3. Grewal DS, Schultz T, Basti S, Dick HB. Femtosecond laser–assisted cataract surgerydcurrent status and future directions. Surv Ophthalmol 2016; 61:103–131 JL. Cataract surgery with femtosecond lasers. Saudi J Ophthalmol 2011; 4. Alio 25:219–223. Available at: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC 3729510/pdf/main.pdf. Accessed December 24, 2016 5. Lim LS, Cheung G, Lee SY. Comparison of spectral domain and sweptsource optical coherence tomography in pathological myopia. Eye 2014; 28:488–491. Available at: https://www.ncbi.nlm.nih.gov/pmc/articles/ PMC3983632/pdf/eye2013308a.pdf. Accessed December 24, 2015 6. Donaldson KE, Braga-Mele R, Cabot F, Davidson R, Dhaliwal DK, Hamilton R, Jackson M, Patterson L, Stonecipher K, Yoo SH, for the ASCRS Refractive Cataract Surgery Subcommittee. Femtosecond laser–assisted cataract surgery. J Cataract Refract Surg 2013; 39:1753–1763. Available at: http://www.ascrs.org/sites/default/files/resources/Femtosecond%20 Cataract%20Surgery%20Review_0.pdf. Accessed December 24, 2016 ~es FP, Costa EF, Cariello AJ, Rodrigues EB, Hofling-Lima AL. 7. Magalha Comparative analysis of the nuclear lens opalescence by the Lens Opacities Classification System III with nuclear density values provided by Oculus Pentacam: a cross-section study using Pentacam Nucleus Staging software. Arq Bras Oftalmol 2011; 74:110–113. Available at: http://www.readcube.com/ articles/10.1590/S0004-27492011000200008. Accessed December 24, 2016 8. The Standardization of Uveitis Nomenclature (SUN) Working Group. Standardization of uveitis nomenclature for reporting clinical data. Results of the First International Workshop. Am J Ophthalmol 2005; 140:509–516 9. Daya SM, Nanavaty MA, Espinosa-Lagana MM. Translenticular hydrodissection, lens fragmentation, and influence on ultrasound power in femtosecond laser–assisted cataract surgery and refractive lens exchange. J Cataract Refract Surg 2014; 40:37–43 10. Abell RG, Darian-Smith E, Kan JB, Allen PL, Ewe SYP, Vote BJ. Femtosecond laser–assisted cataract surgery versus standard phacoemulsification cataract surgery: outcomes and safety in more than 4000 cases at a single center. J Cataract Refract Surg 2015; 41:47–52 11. Bali SJ, Hodge C, Lawless M, Roberts TV, Sutton G. Early experience with the femtosecond laser for cataract surgery. Ophthalmology 2012; 119:891–899 12. Roberts TV, Lawless M, Bali SJ, Hodge C, Sutton G. Surgical outcomes and safety of femtosecond laser cataract surgery; a prospective study of 1500 consecutive cases. Ophthalmology 2013; 120:227–233 13. Chee S-P, Yang Y, Ti S-E. Clinical outcomes in the first two years of femtosecond laser–assisted cataract surgery. Am J Ophthalmol 2015; 159:714–719 14. Talamo JH, Gooding P, Angeley D, Culbertson WW, Schuele G, Andersen D, Marcellino G, Essock-Burns E, Batlle J, Feliz R, Friedman NJ, Palanker D. Optical patient interface in femtosecond laser– assisted cataract surgery: contact corneal applanation versus liquid immersion. J Cataract Refract Surg 2013; 39:501–510 15. Chang JSM, Chen IN, Chan W-M, Ng JCM, Chan VKC, Law AKP. Initial evaluation of a femtosecond laser system in cataract surgery. J Cataract Refract Surg 2014; 40:29–36 16. Chen X, Xiao W, Ye S, Chen W, Liu Y. Efficacy and safety of femtosecond laser-assisted cataract surgery versus conventional phacoemulsification for cataract: a meta-analysis of randomized controlled trials. Sci Rep 2015; 5:13123. Available at: http://www.ncbi.nlm.nih.gov/pmc/articles/ PMC4542520/pdf/srep13123.pdf. Accessed December 24, 2016 17. Conrad-Hengerer I, Al Juburi M, Schultz T, Hengerer FH, Dick HB. Corneal endothelial cell loss and corneal thickness in conventional compared with femtosecond laser–assisted cataract surgery: three-month follow-up. J Cataract Refract Surg 2013; 39:1307–1313 nitz K, Takacs A, Miha ltz K, Kovacs I, Knorz MC, Nagy ZZ. Femtosecond 18. Kra laser capsulotomy and manual continuous curvilinear capsulorrhexis parameters and their effects on intraocular lens centration. J Refract Surg 2011; 27:558–563 19. Dick HB, Schultz T. On the way to zero phaco. J Cataract Refract Surg 2013; 39:1442–1444
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20. Grewal DS, Dalal RR, Jun S, Chou J, Basti S. Impact of the learning curve on intraoperative surgical time in femtosecond laser-assisted cataract surgery. J Refract Surg 2016; 32:311–317 Kova cs AI, cs I, Miha ltz K, Filkorn T, Knorz MC, Nagy ZZ. Central 21. Taka corneal volume and endothelial cell count following femtosecond laserassisted refractive cataract surgery compared to conventional phacoemulsification. J Refract Surg 2012; 28:387–391 22. Ranka M, Donnenfeld ED. Femtosecond laser will be the standard method for cataract extraction ten years from now. Surv Ophthalmol 2015; 60:356–360 23. Mastropasqua L, Toto L, Mattei PA, Vecchiarino L, Mastropasqua A, Navarra R, Di Nicola M, Nubile M. Optical coherence tomography and 3dimensional confocal structured imaging system–guided femtosecond
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laser capsulotomy versus manual continuous curvilinear capsulorhexis. J Cataract Refract Surg 2014; 40:2035–2043 ltz K, Sa ndor GL, Takacs A, Knorz MC, Nagy ZZ. Intraocular 24. Kranitz K, Miha lens tilt and decentration measured by Scheimpflug camera following manual or femtosecond laser-created continuous circular capsulotomy. J Refract Surg 2012; 28:259–263
Disclosure: The Ars Ophthalmica Study Center received research grants from Technolas Perfect Vision GmbH. No author has a financial or proprietary interest in any material or method mentioned.
ARTICLE
Intraindividual comparison between femtosecond laser–assisted and conventional cataract surgery Anna S. Mursch-Edlmayr, MD, Matthias Bolz, MD, Nikolaus Luft, MD, Michael Ring, PhD, Thomas Kreutzer, MD, Christoph Ortner, MD, Matthias Rohleder, MD, Siegfried G. Priglinger, MD
Purpose: To compare the safety and efficacy between femtosecond laser–assisted cataract surgery using the Victus laser system and conventional cataract surgery.
postoperative complications and the effective phacoemulsification time (EPT). Intraocular lens and capsulotomy centration were evaluated using retroillumination slitlamp photography.
Setting: Department of Ophthalmology, Kepler University Hospital, Linz, Austria.
Results: The study enrolled 50 patients. No intraoperative complications occurred in either group. The ECD, CCT, and central retinal thickness were similar between the groups at all follow-up examinations (P > .05). The EPT was not statistically significantly different between the groups (P Z .22). The IOL centration was similar between the groups (P Z .93).
Design: Prospective randomized case series. Methods: Both eyes of patients with age-related cataract were randomized to conventional cataract surgery or femtosecond laser– assisted cataract surgery, both with intraocular lens (IOL) implantation. Postoperative follow-up was at 1 day, 1 week, 1 month, 3 months, and 6 months and comprised corrected distance visual acuity, endothelial cell density (ECD), central corneal thickness (CCT), and central retinal thickness. The main outcomes were intraoperative and
C
ataract extraction is the most frequent ophthalmic surgery.1 Manual creation of a capsulorhexis, which in general is considered the most difficult surgical step, requires individual surgical skills and experience. In addition, excessive transmission of energy during phacoemulsification can cause complications such as capsule tears or corneal endothelium damage.2 Hence, the femtosecond laser was introduced for use in various steps of cataract surgery to increase perioperative safety and precision. Today, 5 femtosecond laser systems for assisting cataract surgery are commercially available.3 Although the systems have many large similarities, they differ in the implemented anterior-segment imaging and in the patient-interface systems.4 The Victus platform (Technolas Perfect Vision GmbH) is the only system with integrated swept-source optical coherence tomography (SS-OCT) imaging, which shows greater sensitivity and a lower signal-to-noise ratio
Conclusion: Femtosecond laser–assisted and conventional cataract surgery using the mentioned system were equally safe and effective. J Cataract Refract Surg 2017; 43:215–222 Q 2017 ASCRS and ESCRS
than the current spectral-domain OCT (SD-OCT) systems.5 In addition, this laser is the only system that uses a dual modality interface. For capsulotomies and lens fragmentations it uses soft docking, for which less applanation (and thus lower vacuum) is needed. Hard docking requires full corneal applanation with higher vacuum, which is necessary for alignment of corneal incisions.6 To our knowledge, the present study is the first to investigate the Victus system in femtosecond laser–assisted cataract surgery using a prospective intraindividual control design. The aim of this study was to evaluate the safety and efficacy of the laser platform in femtosecond laser–assisted cataract surgery versus conventional cataract surgery. PATIENTS AND METHODS This prospective randomized intraindividual comparison study included patients with bilateral age-related cataract who were
Submitted: June 14, 2016 | Final revision submitted: November 21, 2016 | Accepted: November 26, 2016 From the Department of Ophthalmology and the Ars Ophthalmica Study Center (Mursch-Edlmayr, Bolz, Luft, Ring, Ortner, Rohleder, Priglinger), Kepler University Hospital, Linz, Austria; the Department of Ophthalmology (Luft, Kreutzer, Priglinger), Ludwig-Maximilians University, Munich, Germany. Drs. Mursch-Edlmayr and Bolz contributed equally to this work. Supported by a grant from Technolas Perfect Vision GmbH. Corresponding author: Matthias Bolz, MD, Department of Ophthalmology, Kepler University Hospital, Krankenhausstraße 9, 4020 Linz, Austria. E-mail: matthias.bolz@ akh.linz.at. Q 2017 ASCRS and ESCRS Published by Elsevier Inc.
0886-3350/$ - see frontmatter http://dx.doi.org/10.1016/j.jcrs.2016.11.046
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scheduled for cataract surgery in both eyes. The study protocol was reviewed and approved by the local ethics committee and followed the guidelines set forth in the Declaration of Helsinki. Inclusion criteria were a minimum age of 18 years and agerelated cataract. Exclusion criteria were small pupils (!6.0 mm with therapeutic mydriasis) and manifest glaucoma treated with antiglaucoma drugs. One eye of each patient had cataract surgery with conventional phacoemulsification (referred to as conventional cataract surgery), whereas the other eye had femtosecond laser–assisted cataract surgery (referred to as femtosecond cataract surgery). Allocation of the eyes to the respective procedure group was by balanced block randomization using Excel software (Microsoft Corp.).
The Oertli OS3 system (Oertli Instrumente AG) was used for phacoemulsification in both groups. The average phaco power and the equivalent effective phaco time (EPT) were monitored. A Tecnis ZCB00 intraocular lens (IOL) (Abbott Medical Optics, Inc.) was implanted in the capsular bag in both groups to guarantee comparability between each eye and surgical technique. The refractive power of the IOL was calculated with an IOLMaster biometer (Carl Zeiss Meditec AG), which uses the principle of partial coherence interferometry to measure the axial length of the globe. The postoperative therapy regimen was consistent between the 2 groups. It comprised 3 mg/mL tobramycin–1 mg/mL dexamethasone (Tobradex) 6 times daily for 1 week and 0.9 mg/mL bromfenac (Yellox) twice a day for 4 weeks.
Femtosecond Laser The Victus femtosecond platform uses a 1028 nm wavelength diode-pumped solid-state laser that has a 2-piece curved patient interface, including a disposable suction ring clip with a thin liquid layer as a docking interface. Intraoperative imaging is provided by real-time SS-OCT. The maximum possible pulse frequency is 160 kHz, the pulse duration varies between 290 femtoseconds (fs) and 550 fs, and the pulse energy ranges from 0.5 to 10 mJ. By docking the laser assembly, pressure sensors monitor the pressure between the docking device and the eye to allow the surgeon to adjust the positioning. Lens fragmentation options include ring cuts, radial cuts, and a combination of sectorial and quadrant cuts.3 Laser settings followed the manufacturer's specifications and were set according to the cataract degree graded using the nucleus staging system of the Pentacam Scheimpflug imaging device (Oculus Optikger€ate GmbH) (Table 1).
Preoperative and Postoperative Assessments All examiners at the postoperative follow-up visits were blinded to the randomization of the patient. Preoperative assessments comprised corrected distance visual acuity (CDVA) measurement using standard Early Treatment Diabetic Retinopathy Study charts, slitlamp examination including indirect fundoscopy, and measurement of intraocular pressure using Goldmann applanation tonometry. Corneal topography and pachymetry were assessed with a Pentacam Scheimpflug-based topography system. Cataract degree was evaluated using the lens density assessment function with blue-light illumination available in the Scheimpflug system software. The Scheimpflug device nucleus staging classifies the opacity of the lens in 5 stages.7 Endothelial cell density was measured using a dedicated endothelial microscope (EndothelMikroskop EM-2, bon Optic Vertriebsgesellschaft mbH). Central retinal thickness was assessed using SD-OCT (Spectralis, Heidelberg Engineering GmbH). Postoperative assessments comprised CDVA testing, comprehensive slitlamp OCT, and Scheimpflug imaging examinations at 1 day, 1 week, 4 weeks, 3 months, and 6 months. Furthermore, the degree of anterior chamber inflammation (cells and flare) was evaluated at the slitlamp (BC 900, Haag-Streit AG), and the results were recorded using standardized uveitis nomenclature.8 Adverse events were recorded during surgery and at each followup. Individual pain level during surgery was assessed 1 day after each operation using a dedicated patient questionnaire. After femtosecond laser–assisted cataract surgery, patients were asked to define their pain level during the laser procedure on a scale from 1 (no pain) to 5 (intense pain). All patients were asked about their pain level in general during the cataract surgery. After surgery in the second eye, patients were asked to compare the pain level between the 2 types of surgery and which procedure they would recommend.
Surgical Technique Five surgeons (S.P., M.B., C.O., R.S., T.K.) performed the procedures, and the same surgeon operated on both eyes of an individual patient. All surgeons involved in the study had performed at least 1000 conventional cataract surgery procedures. Capsulorhexis creation and lens fragmentation using the phacochop technique were performed manually in the conventional cataract surgery group. The femtosecond laser was used for anterior capsulotomy and lens fragmentation in the femtosecondassisted group. A constant capsulotomy size of 5.0 mm in diameter was maintained by the laser system in the femtosecond group. Capsulotomies were automatically centered on the pupil by the onboard software. After the laser procedure, patients were transferred to the phacoemulsification system. Corneal incisions were created, and the anterior capsule was removed with a forceps.
Table 1. Laser settings of the femtosecond laser for capsulorhexis and lens fragmentation, according to Scheimpflug nucleus staging. Scheimpflug Nucleus Staging Step/Setting
0
1
2
3
4
Diameter (mm)
5200
5200
5200
5200
5200
Energy/pulse (nJ)
7000
7000
7000
7000
7000
7000
7000
7000
7500
8000
4
4
4
8
8
7000
7000
7000
7000
7000
5
3
2
0
0
3000
2500
2000
0
0
Capsulorhexis
Lens fragmentation Energy/pulse (nJ) Number of radial cuts Diameter of radial cuts (mm) Number of circular cuts Diameter of circular cuts (mm)
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FEMTOSECOND LASER–ASSISTED VS CONVENTIONAL CATARACT SURGERY
Comparison of the Capsulotomies and Intraocular Lens Centration At the third follow-up 3 months after surgery, slitlamp photographs were taken to evaluate the centration of the capsulorhexis and the IOL in vivo. The photographs were analyzed by 2 investigators. An ellipse was fitted to the manually defined points of the pupil to calculate the center of the pupil (Figure 1, red cross). Circles were fitted to determine the center of the capsulotomy (Figure 1, blue cross) and the center of the IOL (Figure 1, green cross). Centers were assessed on the basis of x–y coordinates. The IOL centration (DRIP) corresponds to the Euclidian distance between the 2 marks of the center of the IOL and the pupil (equation 1 and Figure 1). The DRIC represents the distance between the center of the capsulotomy and the IOL (equation 2). The DRCP represents the centration of the capsulotomy in reference to the pupil and is calculated by equation 3. rffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi 2 2 DRIP Z (1) xPupil xIOL þ yPupil yIOL rffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi 2 2 DRIC Z xIOL xCapsulotomy þ yIOL yCapsulotomy DRCP Z
rffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi 2ffi 2 xPupil xCapsulotomy þ yPupil yCapsulotomy
parametric data. Paired samples were analyzed using Friedman testing or analysis of variance according to their parametric distribution. Frequencies of nominal scaled variables (postoperative subconjunctival hemorrhage, Descemet folds) were analyzed using the chi-square test. The learning curve for each surgeon (represented by the reduction in EPT) was tested by calculating the Spearman rank correlation coefficient. The level for statistical significance was set at a P value of less than 0.05.
RESULTS The study included 50 patients. The mean age of the 31 women and 19 men was 72 G 6 years. Three patients (6 eyes) were lost to follow-up. The full range of nucleus staging criteria (minimum 0, maximum 4) was covered in both groups (Figure 2). The mean time between surgery in the 2 eyes of each patient was 9.1 G 9 days. Safety
All surgery with the implantation of the IOL was successfully completed in both groups. Haptics were successfully implanted in the capsular bag in all eyes, and no eye required sutures. In the femtosecond group, suction loss followed by redocking of the laser occurred twice (2 patients [4.3%]) and additional epinephrine (Suprarenin) was injected intracamerally during surgery in 7 eyes because of reflective miosis. Three eyes in the conventional cataract surgery group were treated with epinephrine. The difference between the groups was not significant (P Z .31). A remaining bridge of tissue connecting the dissected disk with the anterior capsular bag was observed in 5 eyes (10.6%) in the femtosecond group. The tissue had to be manually disrupted in these cases before it could be removed. No other intraoperative complications, such as capsule rupture or nucleus drop, occurred in either group.
Intraoperative Complications
(2)
(3)
The primary endpoint concerning efficacy was the EPT, which represents the time to emulsify and extract the opaque lens when working at 100% phacoemulsification energy. Furthermore, each surgeon’s experience in femtosecond laser–assisted cataract surgery was correlated with the EPT to determine the learning curve. Capsulotomies of the 2 groups were compared according to the centration of the capsulorhexis and the IOL. A secondary endpoint was the comparison of the individual patient’s perception of both types of surgery. Statistical Analysis Statistical analysis was performed using SPSS software (version 23.0, PASW/SPSS, International Business Machine Corp.). Sample-size calculation was performed based on previously published data for EPT in femtosecond laser–assisted cataract surgery and conventional cataract surgery with a statistical power of 80%.9 Descriptive values are given as the mean G SD. Data were tested for normal distribution using the Kolmogorov-Smirnoff test and qualitatively checked with a Q–Q plot. Means were compared using the Mann-Whitney U test for unpaired nonparametric data and the Student t test for unpaired
Postoperative Complications On the
first day after surgery, a subconjunctival hemorrhage was present in 27 eyes (57.5%) in the femtosecond group and in 1 eye (2.1%) in the conventional group; the difference was statistically significant (P ! .05). Descemet folds were observed in 13 eyes (27.7%) after femtosecond laser–assisted cataract surgery and in 9 eyes (19.1%) after conventional cataract surgery, with no statistically significant difference between the
Figure 1. Left: Diagram of calculation of the IOL centration. The red circle marks the pupil, and the green circle indicates the IOL. Right: Retroillumination slitlamp photograph with marked borders of the pupil (red line), intraocular lens (green line), and capsulotomy (blue line). Crosses mark the centers. The blue cross denotes the center of the capsulotomy (DRIP Z distance between center of pupil [red cross] and the center of the intraocular lens [green cross].
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Intraocular Lens Centration and Capsulotomy Overlap
There was no significant difference in IOL centration with reference to the pupil between the groups. Intraocular lens centration with reference to the capsulotomy was similar between the groups (Table 4). Centration of the capsulotomy with reference to the pupil was better in the femtosecond group than in the conventional group (P ! .05) (Table 4). Patients’ Perceptions
Figure 2. Comparison of the complete intervention time between surgical techniques.
groups (P Z .33). No significant differences in postsurgical inflammation (eg, intracameral cell count 1 day 1 after surgery) were found between groups (P Z .22). One eye in the femtosecond group had a choroidal effusion 1 day after surgery. Restoration to the original condition was achieved by the use of oral prednisolone (75 mg) for 5 days. Influence on Corneal and Retinal Variables
Table 2 shows the analyzed corneal and retinal parameters as well as the P values for the comparisons between the femtosecond group and conventional group. Endothelial cell density, central corneal thickness (CCT), and central retinal thickness were comparable between the groups before surgery and at all follow-ups. Efficacy
The EPT was significantly correlated with the nucleus staging in both groups (femtosecond: r Z 0.3, P Z .03; conventional cataract surgery: r Z 0.5, P ! .01). Although there were no significant differences in the EPT between groups, the complete intervention time was significantly longer in the femtosecond group than in the conventional group (Table 3 and Figure 2). Learning Curve
Nineteen femtosecond laser–assisted cataract surgery procedures were performed by surgeon 1, 9 by surgeons 2 and 3 each, 8 by surgeon 4, and 2 by surgeon 5. The EPT was not statistically significantly reduced with increasing surgical experience in the femtosecond group (no significant correlation for surgeon 1 to 4). For surgeon 5, the sample size did not permit statistical analysis of the learning curve. The results were the same for the duration of the laser procedure, defined as the time between docking and removing the laser system, as well as for the complete surgery time. Visual Acuity and Refraction
Visual acuity was significantly improved beginning 1 day postoperatively in both groups (P ! .01). There was no significant difference in CDVA between the 2 groups at any follow-up. Volume 43 Issue 2 February 2017
Regarding the patients’ response to the questionnaire, the mean pain during the laser procedure was 1.6 G 0.82. The mean during cataract extraction after laser treatment was 1.4 G 0.61. The mean pain during cataract surgery was 1.34 G 0.63 in the conventional group. No significant difference between the groups was found (P Z .26). Thirty patients (63.8%) reported that they had more pain during femtosecond laser–assisted cataract surgery than during conventional cataract surgery. Twenty-seven patients (57.4%) said they would recommend conventional cataract surgery over femtosecond-assisted surgery. DISCUSSION The aim of this study was to evaluate the safety and effectiveness of the Victus femtosecond laser system for cataract surgery. There were no statistically significant differences in EPT, CDVA, ECD, CCT, or central retinal thickness between femtosecond laser–assisted cataract surgery and conventional cataract surgery. The only difference was in capsulotomy centration. To our knowledge, this is the first prospective randomized intraindividual study using this laser system. It focused on safety, evaluated by analyzing surgical or postoperative complications, and on effectiveness, determined by refraction, visual acuity, and capsulorhexis and IOL centration. Regarding safety, no severe intraoperative complications occurred in either group. Femtosecond laser–assisted capsulotomy was incomplete in 10.6% of these eyes. Results regarding capsule tags vary in the literature2,10–13 (Table 5). For the Victus system, incomplete capsulotomy rates between 3.6% and 8.8% have been reported.2,13 As indicated by Roberts et al.,12 the docking process is essential for successful and complete capsulotomies in femtosecond laser–assisted cataract surgery. The relatively high level of suction breaks in the present study compared with rates in the recent literature might be indicative of possible docking issues. There is evidence that corneal folds during the laser procedure resulting from incorrect docking can cause incomplete capsulotomies in femtosecond laser–assisted cataract surgery.14 Hence, the relatively high percentage of capsule tags in our study might be a result of the learning curve.12 In our study, no eye had an anterior capsule tear or IOL dislocation, which is in accordance with the low rates reported in the recent literature2,10–13 (Table 5). The only statistically significant difference between the femtosecond group and conventional group after surgery was the number of patients with a subconjunctival hemorrhage, with a higher incidence in the femtosecond group. This was most likely caused by the vacuum of the docking
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FEMTOSECOND LASER–ASSISTED VS CONVENTIONAL CATARACT SURGERY
Table 2. Between-group comparison of CDVA, ECD, CCT, and central retinal thickness over time. After Surgery Parameter/Group
Before Surgery
1 Day
1 Month
3 Months
6 Months
Mean CDVA (decimal) Femtosecond
0.67 G 0.30
1.10 G 0.28
1.20 G 0.18
1.20 G 0.27
1.20 G 0.23
Conventional
0.70 G 0.3
1.00 G 0.24
1.20 G 0.21
1.20 G 0.24
1.20 G 0.24
.71
.48
.58
.17
.95
Femtosecond
2438.7
2480.8
2165.4
2156.1
2389.1
Conventional
2435.0
2418.9
2165.3
2136.3
2357.6
.82
.17
.64
.7
.75
Femtosecond
d
48.00 G 188.0
128.80 G 403.0
68.60 G 258.4
39.40 G 298.3
Conventional
d
5.70 G 212.5
124.64 G 285.0
97.70 G 323.5
76.80 G 338.6
P value
d
0.26
0.65
0.86
0.57
P value 2
Mean ECD (cells/mm )
P value Mean DECD (cells/mm ) 2
Mean CCT (mm) Femtosecond
551.0
572.3
546.3
553.0
551.6
Conventional
552.1
574.4
536.2
552.8
551.0
.8
.92
.97
.94
.94
Femtosecond
d
19.96 G 95.0
5.31 G 50.7
0.90 G 10.2
0.60 G 10.4
Conventional
d
22.38 G 95.5
16.10 G 70.3
0.70 G 11.3
1.10 G 9.1
P value
d
.88
.7
P value Mean DCCT (mm)
.95
.91
Mean CRT (mm) Femtosecond
285.73 G 29
281.09 G 29
299.60 G 51
292.30 G 33
290.50 G 29
Conventional
285.50 G 25
279.70 G 26
298.40 G 58
290.10 G 29
288.90 G 28
P value
.93
.84
.55
.94
.69
Mean DCRT (mm) Femtosecond
d
3.36 G 10
8.27 G 17
8.59 G 45
5.43 G 10
Conventional
d
3.64 G 6
7.65 G 29
9.09 G 38
5.56 G 8
P value
d
.19
.99
.37
.93
Means G SD D Z differences between initial values and the follow-up values; CCT Z central corneal thickness; CDVA Z corrected distance visual acuity; CRT Z central retinal thickness; ECD Z endothelial cell density
interface.6 The Victus laser uses a contact interface with soft docking for the capsulotomies, which means less vacuum is applied. With the Lensar system (Lensar, Inc.), subconjunctival hemorrhage after femtosecond laser–assisted cataract surgery was reported in 43.8% of patients.15 The Lensar uses a noncontact applanation system, which is known to cause less subconjunctival bleeding.3,14 Thus, based on our rate of approximately 58%, we conclude that soft docking leads to slightly more subconjunctival bleeding than a noncontact system. One eye had a choroidal effusion after femtosecond laser– assisted cataract surgery, which receded after the use of oral
steroids. This complication had not been previously described in the literature.16 We hypothesize that the choroidal effusion was caused by the vacuum during docking of the laser. In our study, there was no statistically significant change in ECD or CCT and no difference between the groups during the 6-month follow-up. In contrast to our finding, another study17 found that corneal endothelial cell loss and corneal thickness were statistically significantly lower after femtosecond laser–assisted cataract surgery than after conventional phacoemulsification, as was the EPT. However, the EPT was similar in both groups in our study, which in part could explain the difference in findings. Volume 43 Issue 2 February 2017
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Table 3. Between-group comparison of EPT, maximum phaco power, and complete intervention time.
Parameter/ Group
Mean ± SD Femtosecond Group
Parameter
Conventional Group
Table 4. Between-group comparison of the centration parameters evaluated by retroilluminated slitlamp photographs.
P Value*
Mean ± SD (mm)
DRIP
2.51 G 1.7
2.82 G 1.6
.22
Femtosecond
Max phaco power (%)
60.10 G 5.94
61.28 G 4.0
.51
Conventional
Intervention time (min)
16.6 G 4.4
10.21 G 2.8
!.01
EPT (s)
0.22 G 0.13 0.23 G 0.13
DRIC
EPT Z effective phacoemulsification time *Mann-Whitney U test
Femtosecond
0.2 G 0.12
Conventional
0.19 G 0.13
DRCP
An early study of femtosecond laser–assisted cataract surgery18 showed that intraoperative complications decreased with the number of surgeries performed, indicating that this new technique has a learning curve. Furthermore, increasing surgical experience was shown to decrease the need for ultrasound (US) energy for phacoemulsification; in a study of surgeons who had performed 1400 femtosecond laser–assisted cataract surgery procedures,19 there was no US exposure in 97% of 100 eyes. A recent study20 challenges these findings by showing a plateau of reduction in EPT after performing 99 femtosecond laser–assisted cataract surgery procedures. We could not prove a learning curve in the current study, which could also be because of the small number of patients and thus the small sample per surgeon. Regarding effectiveness, femtosecond laser assistance did not statistically significantly reduce the EPT or mean phaco energy. Similar and diverse results have been reported.3 In a metaanalysis,16 the EPT was statistically significantly lower in femtosecond laser–assisted cataract surgery; however, laser system variability was not taken into account. In another study,2 the EPT and mean phaco energy were statistically significantly lower in the femtosecond group (56 surgeries with Victus laser) than in the conventional group (63 surgeries). On the other hand, no statistically significant differences in EPT were found between 38 eyes having femtosecond laser– assisted cataract surgery using the Lensx laser system (Alcon)
Femtosecond
0.19 G 0.11
Conventional
0.24 G 0.13
Mean Diff (mm)
P Value*
0.003
.93
0.005
.65
0.54
.049
DRCP Z distance between the center of the capsulotomy and of the pupil; DRIC Z distance between the center of the capsulotomy and of the intraocular lens; DRIP Z distance between the center of the pupil and the center of the intraocular lens *Mann-Whitney U test
and 38 eyes having conventional cataract surgery.21 These contradictory findings could be because different laser systems and settings as well as phacoemulsification techniques were used. In our study, the EPT in the conventional group was very low because the surgeons used the stop-and-chop technique only and not the divide-and-conquer technique. In the present study, the surgery time was statistically significantly longer in the femtosecond group than in the conventional group. Femtosecond laser–assisted cataract surgery is known to be more time consuming because patients are initially positioned under the laser and then moved to the surgical table.22 Hence, logistics seem to be relevant to the flow of the daily clinical routine.6 Regarding lens and capsulotomy centration, results in some studies6,18,23 indicate that femtosecond laser–assisted capsulotomies are more consistent in their precision and that they result in better IOL centration. For example, in a study by Kranitz et al.24 IOLs implanted after femtosecond-assisted cataract surgery had better centration than those implanted after conventional cataract surgery. However, in our study IOL centration in relation to the
Table 5. Studies of intraoperative complications of femtosecond laser–assisted cataract surgery. Percentage Study*/Year Bali 201211 (n Z 200)
Suction Breaks
Anterior Capsule Tags
Anterior Capsule Tears
Lens Dislocation
2.5
10.5
4
2
10.5
2
2
12
(n Z 200)
2.5
12
(n Z 1300)
0.61
1.62
0
0
NA
3.6
1.8
1.8
Roberts 2013 Roberts 2013
Reddy 2013 (n Z 56) 2
10
(n Z 1852)
NA
1.62
1.84
0
13
(n Z 1105)
0.45
8.8
0.81
0
4.3
10.6
0
0
Abell 2015
Chee 2015
Current 2017 (n Z 47) NA Z not available *First author
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FEMTOSECOND LASER–ASSISTED VS CONVENTIONAL CATARACT SURGERY
capsulotomy and to the pupil was similar between the groups. In addition, level of significance was borderline for better centration of the capsulotomy aperture with femtosecond surgery compared with conventional surgery. In addition to safety and effectiveness, patient feedback was evaluated in detail using a standardized questionnaire. The results showed that femtosecond laser–assisted cataract surgery did not offer advantages in terms of the patients’ level of postsurgical satisfaction. The patients’ perception of the 2 surgical procedures was similar. A shortcoming of this study was that 5 surgeons performed the operations in a rather small patient cohort, which could bias the outcomes. Hence, analysis of the learning curve was limited by the small number of femtosecond laser–assisted cataract surgery procedures per surgeon. In addition, surgeons were highly experienced in conventional cataract surgery but not in femtosecond laser–assisted cataract surgery, which might bias the comparison of some outcome parameters (eg, EPT). However, we believe our results are representative of those in a clinical routine at a center where cataract surgery is mainly performed conventionally. Even so, this was the first randomized intraindividual study on the Victus femtosecond laser system and its comparability to other laser systems still has to be clarified in a large-scale study. In conclusion, femtosecond laser–assisted cataract surgery with the Victus femtosecond laser platform showed a good safety profile. Nevertheless, patients who had this procedure had a notably high rate of capsule tags and subconjunctival hemorrhages. No statistically significant reduction in the EPT compared with the EPT for conventional cataract surgery was found. Centration of the capsulotomy was statistically significantly better in the femtosecond laser–assisted cataract surgery group. Patients’ satisfaction was not higher with the femtosecond procedure. All in all, femtosecond laser–assisted cataract surgery based with the Victus system was safe and effective with results similar to those of conventional surgery. WHAT WAS KNOWN Excessive transmission of energy during phacoemulsification in cataract surgery can cause complications, such as damage to the corneal epithelium or capsule tears. Femtosecond laser–assisted cataract surgery has the potential to reduce the phaco energy by softening the lens before US phacoemulsification. Still, results in the literature vary.
WHAT THIS PAPER ADDS The EPT was similar between femtosecond laser–assisted cataract surgery and conventional cataract surgery. The femtosecond laser platform used in the study showed a good safety profile perioperatively as well as during 6 months of follow-up. With femtosecond laser–assisted cataract surgery, a 10% rate of anterior capsule tag was observed. On the first day after femtosecond laser–assisted cataract surgery, approximately 58% of the eyes had a subconjunctival hemorrhage. After having femtosecond laser–assisted cataract surgery in 1 eye and conventional cataract surgery in the fellow eye, more than 50% of the patients said they would recommend the conventional procedure.
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REFERENCES 1. Urh BW. History of ophthalmology at Baylor University Medical Center. Proc (Bayl Univ Med Cent) 2003; 16:435–438. Available at: https://www.ncbi.nlm. nih.gov/pmc/articles/PMC1214563/pdf/bumc0016-0435.pdf. Accessed December 24, 2016 2. Reddy KP, Kandulla J, Auffarth GU. Effectiveness and safety of femtosecond laser–assisted lens fragmentation and anterior capsulotomy versus the manual technique in cataract surgery. J Cataract Refract Surg 2013; 39:1297–1306 3. Grewal DS, Schultz T, Basti S, Dick HB. Femtosecond laser–assisted cataract surgerydcurrent status and future directions. Surv Ophthalmol 2016; 61:103–131 JL. Cataract surgery with femtosecond lasers. Saudi J Ophthalmol 2011; 4. Alio 25:219–223. Available at: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC 3729510/pdf/main.pdf. Accessed December 24, 2016 5. Lim LS, Cheung G, Lee SY. Comparison of spectral domain and sweptsource optical coherence tomography in pathological myopia. Eye 2014; 28:488–491. Available at: https://www.ncbi.nlm.nih.gov/pmc/articles/ PMC3983632/pdf/eye2013308a.pdf. Accessed December 24, 2015 6. Donaldson KE, Braga-Mele R, Cabot F, Davidson R, Dhaliwal DK, Hamilton R, Jackson M, Patterson L, Stonecipher K, Yoo SH, for the ASCRS Refractive Cataract Surgery Subcommittee. Femtosecond laser–assisted cataract surgery. J Cataract Refract Surg 2013; 39:1753–1763. Available at: http://www.ascrs.org/sites/default/files/resources/Femtosecond%20 Cataract%20Surgery%20Review_0.pdf. Accessed December 24, 2016 ~es FP, Costa EF, Cariello AJ, Rodrigues EB, Hofling-Lima AL. 7. Magalha Comparative analysis of the nuclear lens opalescence by the Lens Opacities Classification System III with nuclear density values provided by Oculus Pentacam: a cross-section study using Pentacam Nucleus Staging software. Arq Bras Oftalmol 2011; 74:110–113. Available at: http://www.readcube.com/ articles/10.1590/S0004-27492011000200008. Accessed December 24, 2016 8. The Standardization of Uveitis Nomenclature (SUN) Working Group. Standardization of uveitis nomenclature for reporting clinical data. Results of the First International Workshop. Am J Ophthalmol 2005; 140:509–516 9. Daya SM, Nanavaty MA, Espinosa-Lagana MM. Translenticular hydrodissection, lens fragmentation, and influence on ultrasound power in femtosecond laser–assisted cataract surgery and refractive lens exchange. J Cataract Refract Surg 2014; 40:37–43 10. Abell RG, Darian-Smith E, Kan JB, Allen PL, Ewe SYP, Vote BJ. Femtosecond laser–assisted cataract surgery versus standard phacoemulsification cataract surgery: outcomes and safety in more than 4000 cases at a single center. J Cataract Refract Surg 2015; 41:47–52 11. Bali SJ, Hodge C, Lawless M, Roberts TV, Sutton G. Early experience with the femtosecond laser for cataract surgery. Ophthalmology 2012; 119:891–899 12. Roberts TV, Lawless M, Bali SJ, Hodge C, Sutton G. Surgical outcomes and safety of femtosecond laser cataract surgery; a prospective study of 1500 consecutive cases. Ophthalmology 2013; 120:227–233 13. Chee S-P, Yang Y, Ti S-E. Clinical outcomes in the first two years of femtosecond laser–assisted cataract surgery. Am J Ophthalmol 2015; 159:714–719 14. Talamo JH, Gooding P, Angeley D, Culbertson WW, Schuele G, Andersen D, Marcellino G, Essock-Burns E, Batlle J, Feliz R, Friedman NJ, Palanker D. Optical patient interface in femtosecond laser– assisted cataract surgery: contact corneal applanation versus liquid immersion. J Cataract Refract Surg 2013; 39:501–510 15. Chang JSM, Chen IN, Chan W-M, Ng JCM, Chan VKC, Law AKP. Initial evaluation of a femtosecond laser system in cataract surgery. J Cataract Refract Surg 2014; 40:29–36 16. Chen X, Xiao W, Ye S, Chen W, Liu Y. Efficacy and safety of femtosecond laser-assisted cataract surgery versus conventional phacoemulsification for cataract: a meta-analysis of randomized controlled trials. Sci Rep 2015; 5:13123. Available at: http://www.ncbi.nlm.nih.gov/pmc/articles/ PMC4542520/pdf/srep13123.pdf. Accessed December 24, 2016 17. Conrad-Hengerer I, Al Juburi M, Schultz T, Hengerer FH, Dick HB. Corneal endothelial cell loss and corneal thickness in conventional compared with femtosecond laser–assisted cataract surgery: three-month follow-up. J Cataract Refract Surg 2013; 39:1307–1313 nitz K, Takacs A, Miha ltz K, Kovacs I, Knorz MC, Nagy ZZ. Femtosecond 18. Kra laser capsulotomy and manual continuous curvilinear capsulorrhexis parameters and their effects on intraocular lens centration. J Refract Surg 2011; 27:558–563 19. Dick HB, Schultz T. On the way to zero phaco. J Cataract Refract Surg 2013; 39:1442–1444
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20. Grewal DS, Dalal RR, Jun S, Chou J, Basti S. Impact of the learning curve on intraoperative surgical time in femtosecond laser-assisted cataract surgery. J Refract Surg 2016; 32:311–317 Kova cs AI, cs I, Miha ltz K, Filkorn T, Knorz MC, Nagy ZZ. Central 21. Taka corneal volume and endothelial cell count following femtosecond laserassisted refractive cataract surgery compared to conventional phacoemulsification. J Refract Surg 2012; 28:387–391 22. Ranka M, Donnenfeld ED. Femtosecond laser will be the standard method for cataract extraction ten years from now. Surv Ophthalmol 2015; 60:356–360 23. Mastropasqua L, Toto L, Mattei PA, Vecchiarino L, Mastropasqua A, Navarra R, Di Nicola M, Nubile M. Optical coherence tomography and 3dimensional confocal structured imaging system–guided femtosecond
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laser capsulotomy versus manual continuous curvilinear capsulorhexis. J Cataract Refract Surg 2014; 40:2035–2043 ltz K, Sa ndor GL, Takacs A, Knorz MC, Nagy ZZ. Intraocular 24. Kranitz K, Miha lens tilt and decentration measured by Scheimpflug camera following manual or femtosecond laser-created continuous circular capsulotomy. J Refract Surg 2012; 28:259–263
Disclosure: The Ars Ophthalmica Study Center received research grants from Technolas Perfect Vision GmbH. No author has a financial or proprietary interest in any material or method mentioned.