In modern cataract surgery, patients expect rapid visual recovery and emmetropia and restitution of the anatomy of the anterior segment. Therefore, the natural course of healing has to be supplemented by the use of anti-inflammatory agents to further prevent pain or intraocular inflammation. Phacoemulsification alone has been shown to increase flare values in the anterior chamber as a sign of an increased permeability of the blood–aqueous barrier. Previous studies have shown that the level of ultrasound use influences anterior segment inflammation.1 Reduction of ultrasound phacoemulsification energy is advantageous because it results in decreasing inflammation, enhances patients′ satisfaction, and reduces the risk for endophthalmitis.2 With the introduction of femtosecond laser-assisted cataract surgery for capsulotomy and nuclear fragmentation prior to phacoemulsification,3–11 there is the need to evaluate the safety profile of this technology with respect to its potential to alter the blood–aqueous barrier and the development of subclinical or clinically significant macular edema.
We therefore conducted a prospective randomized and controlled comparative clinical study to investigate the impact of laser-assisted cataract surgery on anterior chamber flare values compared with standard optimized phacoemulsification settings during an interval of 6 months. To our knowledge, this is the first clinical report at a single center based on an intraindividual prospective and randomly distributed study comparing postoperative inflammation by means of cell and flare measurements and evaluation of macular changes with optical coherence tomography laser versus manual techniques.
Patients and Methods
Patients in this trial were scheduled for elective bilateral cataract surgery and implantation of an intraocular lens by a single surgeon (HBD) at the Department of Ophthalmology, Ruhr University of Bochum, Germany. Two hundred eight eyes of 104 patients (58 female, 46 male) were analyzed with a follow-up of 6 months. The average age of the participants was 71.3 years (range: 52 to 85 years). Mean preoperative axial length was 23.55 mm (range: 21.83 to 27.05 mm; median: 23.47 mm) in the laser group compared to 23.54 mm (range: 21.88 to 27.23 mm; median: 23.48 mm) in the standard group. Mean preoperative anterior chamber depth was 2.59 mm (range: 1.63 to 3.76 mm; median: 2.54 mm) in the laser group compared to 2.57 mm (range: 1.51 to 3.63 mm; median: 2.49 mm) in the standard group. Preoperative corrected distance visual acuity was 0.41 logMAR (Snellen 20/50) in the laser group compared to 0.40 logMAR (Snellen 20/50) in the standard group. Exclusion criteria were history of coexistent ocular disease (eg, glaucoma, high myopia, retinal diseases affecting the macula, optic atrophy, or ocular tumors), use of topical or systemic steroids or nonsteroidal anti-inflammatory drugs during the prior 3 months, relevant corneal opacities, age younger than 22 years, or participation in another clinical study. The study received approval of the ethics committee at Ruhr University of Bochum and the tenets of the Declaration of Helsinki were observed. All patients enrolled had visually significant cataracts and were willing to volunteer for the trial after giving a written informed consent.
Prior to the surgery, all patients were treated with topical ofloxacin four times daily for 3 days. According to our standard protocol, no nonsteroidal anti-inflammatory drugs were administered.
The Lens Opacities Classification System III (LOCS III) nuclear opalescence grading score12,13 was used. Preoperative nuclear opalescence was estimated by one independent certified physician using a Haag-Streit BQ 900 Slit lamp (Haag-Streit, Bern, Switzerland) at maximum illumination without any light filtering.
Intraocular lens power calculations were performed using noncontact partial coherence laser interferometry (IOLMaster; Carl Zeiss Meditec, Jena, Germany). Baseline anterior chamber flare values were taken preoperatively with the KOWA laser flare meter (KOWA FM 600; Kowa, Tokyo, Japan) prior to dilating the pupil with topical medication. Laser flare values less than 10 photon counts per millisecond (pc/ms) were considered normal.
Macular spectral-domain optical coherence tomography was performed with the Topcon 3D OCT-2000 (Topcon Corporation, Tokyo, Japan). The three-dimensional scan of the macula was based on 128 horizontal scan lines comprising 512 A-scans in a 6 × 6 mm area. The follow-up function defined the scanning location based on the previously captured/selected image and turned ‘Lock ON’ before the next capture, which enabled the examiner to scan the same position under the same conditions. The values used for statistical analysis were central macular thickness, central foveal thickness, total macular volume, and total foveal volume according to the Early Treatment of Diabetic Retinopathy Study. The center thickness represented the minimal center value of the fovea, whereas the center foveal thickness measurement was the average thickness of the foveal zone (1.0-mm diameter central circle). The total volume was determined as the volume scanned in the 6.0-mm diameter zone and the total foveal volume as the volume in the 1.0-mm diameter central circle.
Intraoperative measurements included the absolute and effective phacoemulsification time. All complications having a potential impact on postoperative healing were recorded.
In some cases, the surgery time and the volume of irrigation fluid instilled in the eye were measured. At the end of surgery, the remaining irrigation fluid was added with the fluid volume necessary to calibrate the ultrasound device. This volume level was subtracted from the unopened balanced salt solution bottle and defined as the amount of balanced salt solution infused into the eye.
The main outcome measurements were laser flare counts from the anterior chamber and changes in macular thickness and volume of all patients undergoing cataract surgery using laser or manual only cataract extraction. Secondary outcome measurements were absolute and effective phacoemulsification time as a function of nuclear density and intraoperative and postoperative complications.
All patients underwent the same preoperative standardized treatment prior to surgery. After positioning the patient on the operating bed, the surgeon opened the corresponding envelope indicating which procedure to choose (ie, femtosecond laser-assisted or standard phacoemulsification).
All eyes underwent small-incision phacoemulsification using topical anesthesia as previously published.14
When randomization determined use of a femtosecond laser-assisted procedure, the patient’s bed was unlocked and turned toward the laser system (Catalys Precision Laser System; OptiMedica, CA) followed by positioning the liquid optics interface on the patient’s eye.
The two-piece liquid optics interface consists of a suction ring and a nonapplanating immersion lens. A 5.0-mm capsulotomy and a standardized lens softening pattern (quadrant grid size) with 350-μm grid spacing were used. This procedure was followed by phacoemulsification using the stop-and-chop technique with the Stellaris phacoemulsification machine (Bausch & Lomb, Rochester, NY) as recently published.14
In both groups, the phacoemulsification and aspiration was followed by polishing of the posterior capsule. Without enlarging the corneal tunnel, a heparin-coated preloaded hydrophobic intraocular lens (Polylens H10; Polytech, Roßdorf, Germany) was injected into the capsular bag. After carefully removing the ophthalmic viscosurgical device, all eyes were patched. Topical ofloxacin and dexamethasone (concentration) eye drops were administered four times daily for the first week, then the dosage gradually decreased over a period of 6 weeks.
All surgeries were performed by the same surgeon (HBD) from March to October 2012.
All descriptive statistical analysis was conducted using SPSS version 19.0 (SPSS, Inc., Chicago, IL). A t test was used to compare the sample means. For correlation, we used Pearson’s correlation coefficient. A total of 104 patients (208 eyes) were enrolled in this study. The sample size was chosen to achieve a statistical power greater than 80% for the group comparison by means of a two-sample Wilcoxon test. A P value less than .05 was considered statistically significant.
Macular edema was quantitatively defined as an increase of central macular thickness of more than three standard deviations above the mean thickness before surgery.15
The mean applied effective phacoemulsification time was 0.035 ± 0.11 seconds in the laser group and 1.39 ± 0.13 seconds in the standard group. Mean LOCS grade was 3.2 (laser group) versus 3.1 (standard group). There was a statistically significant difference in LOCS III grading between treatment groups.
Preoperative mean center thickness was 210 ± 23 μm in the laser group and 205 ± 21 μm in the standard group. Mean center thickness in the laser group was 210 ± 24 μm at 4 days postoperatively, 242 ± 16 μm at 1 week postoperatively, 214 ± 22 μm at 1 month postoperatively, 219 ± 20 μm at 3 months postoperatively, and 215 ± 22 μm at 6 months postoperatively. Mean center thickness in the standard group was 211 ± 32 μm at 4 days postoperatively, 242 ± 19 μm at 1 week postoperatively, 210 ± 34 μm at 1 month postoperatively, 217 ± 29 μm at 3 months postoperatively, and 209 ± 30 μm at 6 months postoperatively (Figure 1). In the laser group, the early postoperative change on day 4 was significant, but there was no further change later. In the standard group, the postoperative changes from 1 week to the last postoperative visit were all significant. The different values between the laser and standard groups at each visit were not significant. The values of the center foveal thickness, total volume, and total foveal volume are demonstrated in Tables A–B (available in the online version of this article) and Table 1. Center foveal thickness values increased until 1 month after surgery and decreased to preoperative values after 3 months in both study groups (Tables A–B). There were no significant differences between groups for any measurements.
Boxplot of retinal center thickness in the femtosecond laser-assisted surgery group (LCS) versus the standard cataract surgery group (Std.) from preoperative values over 6 months follow-up time. The bottom and top of the box are the 25th and 75th percentiles, respectively, and the band near the center is the 50th percentile (median). The bars outside the box indicate the maximum and minimum of all data. A minor outlier (denoted by a small circle) is an observation 1.5× interquartile range outside the central box.
Significance of Macular Data Between Laser and Standard Groups (t test)
Postoperatively, 5 eyes (two in the laser group, three in the standard group) developed clinically significant macular edema with reduced corrected distance visual acuity. All details about those patients, their visual acuity, and comorbidities are presented in Table C (available in the online version of this article). Five patients (3 in the standard group and 2 in the laser group) developed a clinically significant macular edema and were treated with 500 mg dorzolamide (oral), and non-steroidal anti-inflammatory drugs (oral and local).
The preoperative laser flare values averaged 8.7 ± 4.8 pc/ms in the laser group and 8.5 pc/ms in the standard group. The difference was not statistically significant.
Laser flare photometry in the standard group showed significantly higher levels on examination 2 hours after surgery (Table 2). The laser flare values were 16.7 ± 5.8 pc/ms in the laser group and 18.8 ± 6.5 pc/ms in the standard group. This difference was statistically significantly different (P = .033). Three days after surgery, values decreased to 14.0 ± 6.4 pc/ms in the laser group and 14.6 ±6.1 pc/ms in the standard group (P = .558). At the 1 week postoperative visit, laser flare values were 13.1 ± 6.2 pc/ms in the laser group and 14.3 ± 7.1 pc/ms in the standard group (P = .283).
Comparison of Laser Flare Values Between the Laser and Standard Groups (photon counts/millisecond)
The following positive correlations could be detected: laser flare values in the laser group at 1 week (0.293; P < .05) and 1 month (0.301; P < .01) correlated with center thickness and laser flare values at 1 month (0.289; P < .05) with center foveal thickness. Furthermore, laser flare values at 1 month (0.262; P < .05) correlated with center thickness at 3 months. In the standard group, laser flare values at 1 week (0.393; P < .01) and 1 month (0.463; P < .01) correlated with center thickness at 1 month and laser flare values at 1 week (0.251; P < .05) and 1 month (0.269; P < .05) with center foveal thickness. Furthermore, laser flare values at 1 month (0.271; P < .05) correlated with center thickness at 3 months.
The surgery time and the irrigation fluid that went into the eye demonstrated no significant difference between the laser and standard groups.
All surgeries were documented by HD-videotaping and no intraoperative complications appeared in any group.
Elevated intraocular pressure values were measured immediately postoperatively in 3 eyes (laser group: 28 mm Hg; standard group: 25 and 31 mm Hg) and at 1 week postoperatively in 1 eye (standard group: 23 mm Hg).
In this prospective randomized clinical trial, we analyzed the postoperative inflammation of the anterior segment by measuring laser flare. Macular thickness was also measured by spectral-domain optical coherence tomography. Our findings suggest that femtosecond laser-assisted cataract surgery exhibits no significant differences in the occurrence of macular edema when compared to standard phacoemulsification. The surgical skills and experience (which influence surgical trauma surgery time and typically use of ultrasound energy, and therefore affect postoperative inflammation course and perhaps the incidence and magnitude of macular edema) are other issues to be addressed.
In randomized, controlled clinical trials, preoperative and postoperative application of nonsteroidal anti-inflammatory eye drops showed positive effects on preventing a perifoveal thickening on optical coherence tomography or clinical macular edema.16 The use of a femtosecond laser for cataract surgery may have only a slight additional effect for experienced surgeons.
The increase of macular thickness at the 1-month postoperative visit is comparable to the findings of other research groups that evaluated postoperative changes in macular thickness in patients after uneventful cataract surgery.17–22 No significant differences in the absolute macular thickness values could be detected between the laser and standard groups. No side effects from femtosecond laser technology (eg, gas bubbles and increase of intraocular pressure or temperature) increased the risk for developing macular edema.
Slightly better results were achieved in treating postoperative clinical macular edema in the eyes receiving laser-assisted cataract surgery, but the power of this analysis is due to the incidence of clinical macular edema in the study group.
This research is a prelude to a specific study on the comparative outcomes of standard and femtosecond laser-assisted cataract surgery with regard to postoperative inflammation for patients at high risk, such as those who have uveitis or diabetes, for developing macular edema.
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Significance of Macular Data Between Laser and Standard Groups (t test)
||Center Foveal Thickness
||Total Foveal Volume
|Postoperative, 4 days
|Postoperative, 1 week
|Postoperative, 1 month
|Postoperative, 3 months
|Postoperative, 6 months
Comparison of Laser Flare Values Between the Laser and Standard Groups (photon counts/millisecond)
||Laser Group Mean ± SD (Min–Max)
||Standard Group Mean ± SD (Min–Max)
||P (Between Groups)
||8.7 ± 4.8 (1.0–14.2)
||8.5 ± 5.0 (1.2–14.3)
|Postoperative 2 hours
||16.7 ± 5.8 (5.2–27.7)
||18.8 ± 6.5 (5.2–29.9)
|Postoperative 4 days
||14.0 ± 6.4 (1.1–27.1)
||14.6 ± 6.1 (3.7–29.7)
|Postoperative 1 week
||13.1 ± 6.2 (1.4–28.2)
||14.3 ± 7.1 (3.3–29.6)
|Postoperative 1 month
||8.5 ± 4.6 (1.0–13.8)
||8.6 ± 4.5 (1.1–14.1)