Search Results (9)

Background: Managing post-keratoplasty astigmatism remains challenging. Even though graft viability is the main concern in keratoplasty, astigmatism might hinder vision recovery following a successful corneal transplant. Photorefractive keratectomy (PRK) and topography-guided PRK may be options for correcting refractive errors in patients who underwent keratoplasty. The aim of the study was to compare the results of PRK and topography-guided PRK in patients who had undergone corneal keratoplasty. Methods: This study was conducted at the Chair and Ophthalmology Clinic of the Medical University of Silesia, at the Railway Hospital Katowice, from 2023 to 2024. Patients who underwent penetrating keratoplasty due to keratoconus or corneal scar (post-traumatic and post-inflammatory) with a residual spherical myopic or mixed myopic astigmatic refractive defect were included in this study. The studied patients were divided into two groups: 15 patients underwent PRK and 15 patients underwent topography-guided PRK. Each participant underwent a preoperative examination, including uncorrected visual acuity (UCVA) and best spectacle-corrected visual acuity (BSCVA) measured on the Snellen chart (LCD panel for visual acuity testing Frey CP-400, Optotech Medical, Niepołomnice, Niepołomice, Poland), cycloplegic refraction, corneal pachymetry and topography (Schwind Sirius+, Pentacam), wavefront aberrations (Schwind Peramis, Pentacam), applanation tonometry, and anterior and posterior segment examinations, conducted at baseline and 1, 3, 6, and 12 months. Results: Keratoconus was the most common reason for keratoplasty (80% vs. 60%). Following PRK, the mean KI in group (1) decreased significantly to 43.88 ± 3.64 (p < 0.001), and in the group (2), the mean diopters decreased significantly after the intervention to 46.46 ± 2.80 (p < 0.001). The mean spherical refractive error in group (2) changed significantly after the intervention, reaching −2.72 ± 1.28 D (p < 0.001). The mean cylinder in group (1) changed significantly after PRK to have a mean of −2.75 ± 1.44 D (p < 0.001). Also, in group (2), it changed significantly after the intervention to have a mean of −2.95 ± 1.99 D (p < 0.001). There was a significant increase in both uncorrected visual acuity (UCVA) and best-corrected visual acuity (BCVA) after topography-guided PRK at all the follow-up points of 1, 3, 6, and 12 months (p < 0.001). The mean higher-order corneal aberrations (HOAs) after topography-guided PRK were 1.33 ± 0.50, ranging from 0.22 to 2.34 (p < 0.001). Conclusions: Topography-guided PRK is safer and more effective in correcting aberrations and refractive errors after corneal keratoplasty than regular PRK. Additionally, topography-guided PRK reduces high-order aberrations by utilizing advanced topographic mapping of the cornea, enabling precise customization of the treatment to address individual corneal surface irregularities. Full article

Objectives: To report a novel application within the USA of excimer ablation for the normalization of central corneal refractive irregularity, combined with higher fluence CXL in the effective management and visual rehabilitation of progressive keratoconus. Methods: 17 consecutive cases with progressive keratoconus were treated with corneal surface excimer laser ablation normalization using topography-guided (Contura) myopic ablation for customized corneal re-shaping with a 6 mm optical zone. The epithelial removal was accounted for by adding a −2.75 diopter correction to this topography-guided normalizing surface ablation followed by a second wavefront-optimized hyperopic excimer treatment of +2.75 diopters also with a 6 mm optical zone. The two sequential excimer ablations applied on the intact epithelium were followed by corneal crosslinking (CXL). Visual acuity, refraction, and keratoconus documentation via keratometry, topography, and pachymetry, as well as endothelial cell density were evaluated over 36 months. Results: Keratoconus stabilized in all cases. The severity and stage of keratoconus determined by the Amsler–Krumeich criteria improved for the OD from an average of 2.2 to 1. The median UDVA showed marked improvement at one-year follow-up (all values in LogMAR), from 0.8 preoperative to 0.3 at 12 months, and was stable through the 3 years at 0.3. The median CDVA increased from 0.5 to 0.1 at 1 year and was stable at 0.1 at 3 years. The average minimal corneal thickness decreased from 466 μm to 396 μm, as recorded the first year postoperatively, and then slightly increased to 405 μm at the 3-year follow-up. Conclusions: We introduce herein the initial clinical data for the use of a novel, off-label therapeutic excimer laser surface ablation application. It was designed to perform both epithelial removal and anterior corneal stroma reshaping and combined with CXL to apply the Athens Protocol CXL with US excimer laser-approved specifications. Full article

Myopic traction maculopathy (MTM) affects 20% of eyes with pathologic myopia (PM). The MTM Staging System (MSS), published in 2020, describes the nomenclature of MTM as well as a proposal of pathogenesis, natural evolution, and prognosis. A study of customized treatment for each stage of MTM has been published previously and suggested to treat maculoschisis and detachment by placing a macular buckle (MB) behind the macula to push the sclera towards the retina, selecting pars plana vitrectomy (PPV) only in cases where a macular hole is associated with MTM. We hereby describe a new model of a macular buckle, known as NPB, and an NPB loading device, with the aim to standardize the surgical technique and render it more user friendly, efficient, and safe. Macular buckle is an effective and safe procedure to treat maculoschisis and macular detachment in MTM. We recommend using it as a unique and first-line treatment. Full article

This study aimed to investigate the reproducibility of pupil size measurements over time and between reading methods when comparing human-assisted reading to automated reading. Pupillary data were analyzed on a subset of myopic children enrolled in a multicenter randomized clinical trial on myopia control with low-dose atropine. Pupil size measurements were obtained prior to randomization at two time points (screening and baseline visits) using a dedicated pupillometer under mesopic and photopic conditions. A customized algorithm was built to perform automated readings, allowing comparisons between human-assisted and automated readings. Reproducibility analyses followed the principles of Bland and Altman and included the calculation of the mean difference between measurements and limits of agreement (LOA). We included 43 children. Mean (standard deviation) age was 9.8 (1.7) years and 25 (58%) children were girls. Using human-assisted readings, reproducibility over time showed mesopic mean difference of 0.02 mm with LOA from −0.87 mm to 0.91 mm, whereas photopic mean difference was −0.01 mm with LOA from −0.25 mm to 0.23 mm. Reproducibility between human-assisted and automated readings was also higher under photopic conditions, with mean difference of 0.03 mm and LOA from −0.03 mm to 0.10 mm at screening and mean difference of 0.03 mm and LOA from −0.06 mm to 0.12 mm at baseline. Using a dedicated pupillometer, we found that examinations performed under photopic conditions demonstrated higher reproducibility over time and between reading methods. We speculate whether mesopic measurements are sufficiently reproducible to be monitored over time. Furthermore, photopic measurements may be of greater relevance when evaluating the side effects of atropine treatment, such as photophobia. Full article

Almost every supplier faces uncertain and time-varying demand. E-commerce and online shopping have given suppliers unprecedented access to data on customers’ behavior, which sheds light on demand uncertainty. The main purpose of this research project is to provide an analytic tool for decentralized supply channel members to devise optimal long-term (multi-period) supply, pricing, and timing strategies while catering to stochastic demand in a diverse set of market scenarios. Despite its ubiquity in potential applications, the time-dependent channel optimization problem in its general form has received limited attention in the literature due to its complexity and the highly nested structure of its ensuing equilibrium problems. However, there are many scenarios where a single-period channel optimization solution may turn out to be myopic as it does not consider the after-effects of current pricing on future demand. To remedy this typical shortcoming, using general memory functions, we include the strategic customers’ cognitive bias toward pricing history in the supply channel equilibrium problem. In the form of two constructive theorems, we provide explicit solution algorithms for the ensuing Nash–Stackelberg equilibrium problems. In particular, we prove that our recursive solution algorithm can find equilibria in the multi-periodic variation of many standard supply channel contracts such as wholesale, buyback, and revenue-sharing contracts. Full article

In this work we try to understand the real effect of increase in aberrations after Femto-LASIK surgery on the patient’s final visual quality, specifically when the visual acuity measurement is considered. A clinical study with 37 eyes of 20 patients that underwent myopic Femto-LASIK surgery and different personalized eye model simulations were carried out. In clinical study, correlations between pre- and postoperative parameters with visual acuity were analysed. Eye simulations (based on real data) provided simulations of vision quality before and after surgery. Our main results showed a significant increase in aberrations was obtained after surgery; however, no differences were found between the preoperative corrected distance visual acuity (CDVA) and the postoperative uncorrected distance visual acuity (UDVA). This absence of differences in visual quality could be explained by performing different simulations on three eyes that would cover most of the possible clinical situations. Simulations were implemented considering a pupil size of 2.5 mm and the personalized data of each patient. Results showed that final visual acuity (VA) change are determined by the final high-order aberrations (HOAS) and their increase after surgery but measured under photopic conditions. In conclusion, customized analysis of higher-order aberrations in scotopic pupils better predicts patient visual acuity after Lasik surgery. Full article

Myopic macular foveoschisis maculopathy is an eye disease that is treated, in most cases, with surgical intervention, in which a macular buckle is applied to restore eye anatomy and functionality. A macular buckle is a type of exoplant that comes in various designs and sizes. Often, they are difficult to apply or they do not fit properly in the eye geometry since they have a generic form. In this work, the effort to develop the most suitable tailor-made macular buckle for each individual patient for treating myopic traction maculopathy is studied. Pattern recognition techniques are applied to the patient’s Computed Tomography (CT) data to develop the exact 3D geometry of the eye. Using this 3D geometry, the trajectory of the buckle is fitted and the buckle is formed, which is then 3D-printed with biocompatible polymer materials. It is expected that the power of technology will be used to activate the most precise approach for each individual patient. Considering the possible complications and technical difficulties of other surgical methods, the customized macular buckle is an appropriate, easy-to-use, and most precise piece of medical equipment for the treatment of myopic traction maculopathy. Full article

In a previous work, a parsimonious topic model (PTM) was proposed for text corpora. In that work, unlike LDA, the modeling determined a subset of salient words for each topic, with topic-specific probabilities, with the rest of the words in the dictionary explained by a universal shared model. Further, in LDA all topics are in principle present in every document. In contrast, PTM gives sparse topic representation, determining the (small) subset of relevant topics for each document. A customized Bayesian information criterion (BIC) was derived, balancing model complexity and goodness of fit, with the BIC minimized to jointly determine the entire model—the topic-specific words, document-specific topics, all model parameter values, and the total number of topics—in a wholly unsupervised fashion. In the present work, several important modeling and algorithm (parameter learning) extensions of PTM are proposed. First, we modify the BIC objective function using a lossless coding scheme with low modeling cost for describing words that are non-salient for all topics—such words are essentially identified as wholly noisy/uninformative. This approach increases the PTM’s model sparsity, which also allows model selection of more topics and with lower BIC cost than the original PTM. Second, in the original PTM model learning strategy, word switches were updated sequentially, which is myopic and susceptible to finding poor locally optimal solutions. Here, instead, we jointly optimize all the switches that correspond to the same word (across topics). This approach jointly optimizes many more parameters at each step than the original PTM, which in principle should be less susceptible to finding poor local minima. Results on several document data sets show that our proposed method outperformed the original PTM model with respect to multiple performance measures, and gave a sparser topic model representation than the original PTM. Full article

In service to sustainable development, consumers have begun to prefer green products for their special environmental characteristics, and many enterprises are introducing new products to improve their competitiveness, but this tactic may not work if customers are strategic, as they might choose to defer purchasing decisions while prices are high and wait for lower prices in the future. Considering the differences in purchase behavior, we divided customers into two groups—strategic customers and myopic customers. Furthermore, we distinguished three types of strategic customers according to their different preferences to analyze the optimal pricing and greenness strategies in sustainable supply chain in strategic customer scenarios. Our results led to the following conclusions. (1) Strategic customers’ individual preferences can affect optimum equilibrium and that a higher purchase price threshold can stimulate the manufacturer to improve greenness and set a higher price, while a higher greenness purchase threshold and purchase value threshold will force manufacturer to set a lower price. (2) We observed that strategic customers can increase demand and vender profit. As the number of strategic customers increases, selling price and greenness will experience downward trends in a price threshold scenario but upward trends in greenness threshold and value threshold scenarios. (3) A firm can take measures to mitigate the effects of strategic customers by adjusting price and greenness dynamically according to price and greenness sensitivity, which can play a leading role in actively influencing strategic customer behavior. Full article