SEMI-ACTIVE DAMPING PERFORMANCE OF IRON PARTICLE FILLED SILICONE RUBBER

The aim of this work was to design, produce and evaluate a demonstrator to visualize the magneto-induced damping behaviour of materials. In contrast to standard materials, the damping coefficient of iron particle filled silicone rubbers can be controlled by a semi-active magnetic field. This field effect should be characterized in order to evaluate the suitability of these magnetorheological silicone elastomers for the use in different configurations and applications

COMPARISON OF VIRTUAL FIELDS METHOD, PARALLEL NETWORK MATERIAL MODEL AND FINITE ELEMENT UPDATING FOR MATERIAL PARAMETER DETERMINATION

Extracting material parameters from test specimens is very intensive in terms of cost and time, especially for viscoelastic material models, where the parameters are dependent of time (frequency), temperature and environmental conditions. Therefore, three different methods for extracting these parameters were tested. Firstly, digital image correlation combined with virtual fields method, secondly, a parallel network material model and thirdly, finite element updating. These three methods are shown and the results are compared in terms of accuracy and experimental effort

Intraocular Lens Power Calculation after Small Incision Lenticule Extraction

With more than 1.5 million Small Incision Lenticule Extraction (SMILE) procedures having already been performed worldwide in an ageing population, intraocular lens (IOL) power calculation in post-SMILE eyes will inevitably become a common challenge for ophthalmologists. Since no refractive outcomes of cataract surgery following SMILE have been published, there is a lack of empirical data for optimizing IOL power calculation. Using the ray tracing as the standard of reference - a purely physical method that obviates the need for any empirical optimization - we analyzed the agreement of various IOL power calculation formulas derived from the American Society of Cataract and Refractive Surgeons (ASCRS) post-keratorefractive surgery online calculator. In our study of 88 post-SMILE eyes, the Masket formula showed the smallest mean prediction error [-0.36 +/- 0.32 diopters (D)] and median absolute error (0.33D) and yielded the largest percentage of eyes within +/- 0.50D (70%) in reference to ray tracing. Non-inferior refractive prediction errors and +/- 0.50D accuracies were achieved by the Barrett True K, Barrett True K No History and the Potvin-Hill formula. Use of these formulas in conjunction with ray tracing is recommended until sufficient data for empirical optimization of IOL power calculation after SMILE is available

Impact of extreme (flat and steep) keratometry on the safety and efficacy of small incision lenticule extraction (SMILE)

Little is known about the connection between preoperative keratometry and postoperative results of myopic small-incision lenticule extraction (SMILE). To determine the influence of extreme (flat and steep) corneal keratometry on the safety and efficacy of SMILE, the databases of the Department of Ophthalmology, Ludwig-Maximilians-University Munich, Germany, and SMILE Eyes Linz, Austria, were screened for patients with steep and flat keratometry who had undergone SMILE. In this cross-sectional matched comparative cohort study, eyes with markedly flat (< 42.0 diopters; D) or steep (≥ 47.0D) preoperative corneal keratometry were matched to a cohort of eyes with regular keratometry (42.0-46.9D) by preoperative manifest refractive spherical equivalent and cylinder, age, corrected distance visual acuity and surgical SMILE parameters. The standardized graphs and terms for refractive surgery results were applied to compare the three groups. Changes in higher order aberrations (HOAs) were evaluated on Scheimpflug imaging. In total, 63 eyes (21 each) of 54 patients with a mean refractive spherical equivalent of - 5.21 ± 1.59 D were followed up for a mean of 9.2 ± 6.1 (minimum ≥ 3) months. Mean baseline keratometry was 41.3 ± 0.7D (flat), 45.5 ± 1.0D (regular) and 47.7 ± 0.6D (steep) (p < 0.0001). Compared to the regular group, the flat and the steep cornea group resulted in a non-inferior percentage of eyes within ± 0.50 D of target refraction (p = 0.20), uncorrected distance visual acuity (p = 0.95) and corrected distance visual acuity (p = 0.20). Flat corneas however experienced a stronger induction of spherical aberration (SA) compared to the steep group (p = 0.0005). In conclusion, non-inferior outcomes of SMILE can also be expected in eyes with steep (≥ 47D) or flat (< 42D) preoperative keratometry, while SMILE however induces more SA in eyes with a flat keratometry

Ex vivo excimer laser ablation of cornea guttata and ROCK inhibitor‐aided endothelial recolonization of ablated central cornea

Purpose To determine whether excimer laser ablation of guttae is a viable strategy for removal of diseased tissue in Fuchs' endothelial corneal dystrophy (FECD) on excised human Descemet membranes and whether an excimer laser‐created wound on healthy human corneas ex vivo is recolonized with corneal endothelial cells. Methods Descemet membranes of FECD patients and corneal endothelium of normal human corneas were ablated ex vivo using an excimer laser licensed for glaucoma surgery. Specimens were kept in cell culture medium supplemented with 10 μm of rho‐kinase inhibitor ripasudil. Corneal endothelial cell regeneration was observed using light and electron scanning microscopy. Furthermore, the whole corneal samples were evaluated by haematoxylin/eosin staining and immunohistochemical analysis using antibodies against Na+/K+‐ATPase. Results Guttae and corneal endothelium could be ablated with an excimer laser without total ultrastructural damage to the Descemet membrane or stroma. Nearly complete endothelial wound closure was accomplished after 26–38 days in treated corneas. Light and electron scanning microscopy suggested the establishment of a layer of flat endothelial cells. Additionally, Na+/K+‐ATPase expression could only be observed on the inner side of the Descemet membrane. Conclusion Our proof of concept study demonstrated that excimer lasers can be used to ablate diseased tissue from excised FECD Descemet membranes ex vivo. Additionally, corneal endothelial cells recolonize a previously ablated endothelial area in healthy human corneas ex vivo under treatment with ripasudil. Thus, our results are the first experimental basis to further investigate the feasibility of an excimer laser ablation as a graftless FECD treatment option

Semiautomated SD-OCT Measurements of Corneal Sublayer Thickness in Normal and Post-SMILE Eyes

Purpose:To test the reliability of a novel algorithm for measuring corneal epithelial thickness (ET) and stromal thickness of normal eyes and post-small incision lenticule extraction (SMILE) corneas with spectral-domain optical coherence tomography.Methods:In this prospective observational study, a customized semiautomated software algorithm was developed and applied to measure corneal ET and stromal thickness along the horizontal corneal meridian. Measurements were performed by 2 examiners in a randomized fashion on a sample of 40 eyes with previous SMILE for treatment of myopia and a control group composed of 40 normal eyes. The intrauser repeatability and interuser reproducibility were analyzed by calculating typical indices including the coefficient of variation and intraclass correlation coefficient. Corneal sublayer thickness profiles were compared between normal and post-SMILE eyes.Results:In both groups, coefficients of variation were 3.2% or lower and intraclass correlation coefficients were 0.929 or higher indicating excellent reliability of the measurement method. Central ET was on an average 6 m greater in post-SMILE corneas (58.8 5.4 m) compared with normal eyes (52.8 +/- 4.0 m), with P < 0.01. Also, there was greater interindividual variability in ET in post-SMILE corneas and their horizontal epithelial profile seemed to show a lenticular appearance.Conclusions:Highly favorable indices of measurement reliability were achieved for this novel method of measuring corneal sublayer pachymetry not only in normal eyes but also in eyes with previous SMILE. The corneal ET profile was significantly altered in post-SMILE eyes compared with normal corneas

Intravitreal ranibizumab versus isovolemic hemodilution in the treatment of macular edema secondary to central retinal vein occlusion: Twelve-month results of a prospective, randomized, multicenter trial

PURPOSE This is a prospective, randomized, multicenter, investigator-initiated trial to evaluate the 12-month effectiveness of isovolemic hemodilution (IH) with prompt versus deferred intravitreal injections (IVI) of ranibizumab 0.5 mg for the treatment of macular edema secondary to early central retinal vein occlusion (CRVO). METHODS Eyes with macular edema due to CRVO having occurred not more than 8 weeks previously received either monthly ranibizumab IVI in combination with IH (group I, n = 28) or IH alone (group II, n = 30). From month 2 to 12, the patients in both groups could be treated with monthly intravitreal ranibizumab. The main outcome variables were gain of visual acuity and the course of central retinal thickness as measured with optical coherence tomography. RESULTS At 12 months, eyes in group I on average gained +28.1 (±19.3) letters compared to +25.2 (±20.9) letters in group II (p = 0.326). This result was achieved with significantly fewer injections in group II. Additionally, 30% of the eyes in group II did not need ranibizumab IVI during the 12 months of the trial. CONCLUSION Ranibizumab IVI in addition to IH proved to be highly effective in increasing visual acuity and reducing macular edema secondary to CRVO. Initial IH in early CRVO may be a first treatment option in patients anxious about IVI

Modern Corneal Eye-Banking Using a Software-Based IT Management Solution

Background. Increasing government legislation and regulations in manufacturing have led to additional documentation regarding the pharmaceutical product requirements of corneal grafts in the European Union. The aim of this project was to develop a software within a hospital information system (HIS) to support the documentation process, to improve the management of the patient waiting list and to increase informational flow between the clinic and eye bank. Materials and Methods. After an analysis of the current documentation process, a new workflow and software were implemented in our electronic health record (EHR) system. Results. The software takes over most of the documentation and reduces the time required for record keeping. It guarantees real-time tracing of all steps during human corneal tissue processing from the start of production until allocation during surgery and includes follow-up within the HIS. Moreover, listing of the patient for surgery as well as waiting list management takes place in the same system. Conclusion. The new software for corneal eye banking supports the whole process chain by taking over both most of the required documentation and the management of the transplant waiting list. It may provide a standardized IT-based solution for German eye banks working within the same HIS