Study Design
In this prospective randomized intraindividual comparative study, cataract surgery with PPLC was performed in one eye (PPLC group), regular cataract surgery without PPLC was performed in the other eye of the same patient (Control group). All surgeries were performed between at Ruhr University Eye Hospital, Bochum, Germany by the same experienced surgeon (HBD) with the same plate haptic intraocular lens (CT Asphina, Zeiss, Oberkochen, Germany). Institutional review board approval was received (Ethic Committee of the Ruhr University, Bochum, Germany, 15-5234), and the study was registered in the German Clinical Trials Register (DRKS00010845). The study was performed in accordance with the tenets of the Declaration of Helsinki, and all participants provided written informed consent.
Eligibility criteria
To be included in the trial, patients had to be at least 22 years of age, cataract-related reduction in visual acuity to 0.8 or less. Exclusion criteria were previous ocular trauma, any type of glaucoma, pseudoexfoliation syndrome, corneal scars, Fuchs dystrophy, ocular tumor, macular degeneration, pupil diameter smaller than 6.0 mm, intraoperative floppy-iris syndrome, ocular inflammation, previous ocular surgery, missing an eye, pregnancy, diabetes mellitus, a vascular disease, chronic kidney disease, uncontrolled hypertension, and concurrent participation in another clinical study.
Preoperative examination
In addition to a basic ophthalmologic examination consisting of measuring visual acuity, refraction, intraocular pressure (IOP) and examining the eye's morphology with the slit lamp and by funduscopy and macular thickness (SD-OCT, Spectralis, Heidelberg Engineering GmbH, Heidelberg, Germany) were measured.
Randomization
The randomization process was described in detail beforehand. Briefly, a corresponding envelope with the information about the receiving procedure was opened by the surgeon in the operating room and all cases were HD-videotaped.
Surgical technique
The surgical technique has been described in detail recently. In short: Both eyes underwent standard cataract surgery. The eye with PPLC was docked to the femtosecond laser system after IOL implantation and wound hydration (Catalys Precision Laser System, Johnson&Johnson Vision, Irvine, CA, USA). The cylindrical treatment zone of the anterior capsulotomy was manually positioned on the posterior capsule, which was placed in the first third of the treatment zone (diameter 3.5 mm, incision depth 600 to 800 µm, horizontal spot spacing 5 µm, vertical spot spacing 10 µm, pulse energy 8 µJ). Care was taken to avoid positioning the treatment zone within the IOL optic or the anterior hyaloid. Immediately before the laser treatment, the capsulotomy position was confirmed on the live OCT. Next, the PPLC was performed (treatment time from 2.4 to 2.6 seconds). Immediately after treatment, the posterior capsule disc started to contract, which could be seen on the infrared camera on the computer screen. The disk did not move into the vitreous because the anterior hyaloid membrane was left intact. In the next step, the eye was undocked, and the patient swiveled back under the operating microscope to determine whether the posterior capsulotomy was well centered. No further intraocular manipulations were made. Antibiotic and steroidal ointments (ofloxacin, prednisolone) were applied, and the eye was covered with a patch.
Postoperative examination
The patients of our first trial (6 months follow up) were invited for an additional examination 2 years after surgery by mail and phone-call. Beside the basic ophthalmic examinations, intraocular pressure, corneal endothelial cell count, macular thickness and the PCO were investigated. Patients with Nd:YAG laser capsulotomy were not included in the PCO-analysis. For the analysis two slit lamp photographs in mydriasis were taken in retro-illumination and merged into an image with optimal lighting. The PCO behind the IOL-optic was objectively analyzed using a computer-based software (Evaluation of Posterior Capsule Opacification 2000, ePCO 2000, V6.2, Poweronline, Berlin, Germany). For the total PCO-score the density of the opacification was graded by the software (0/none to 4/severe) and multiplied with the affected area behind the IOL. The measurements were made by the same experienced observer (TS). In addition, the visibility of the curled-up capsule disc was analyzed.
Statistical Analysis
All descriptive statistical analysis was conducted using SPSS Version 28.0 (SPSS, Inc., Chicago, IL). The Friedman and post-hoc Wilcoxon signed rank tests were conducted to examine differences in the groups. A p value of less than 0.05 was considered statistically significant. To compare between groups, the Mann–Whitney U test was performed. A p value of less than .005 was considered statistically significant. Continuous variables were described with mean, standard deviation, median, and minimum and maximum values. Boxplots were used for the graphical illustration.