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Ultra-Low Surface Brightness Imaging with the Dragonfly Telephoto Array
We describe the Dragonfly Telephoto Array, a robotic imaging system optimized for the detection of extended ultra-low surface brightness structures. The array consists of eight Canon 400 mm f/2.8 L IS II USM telephoto lenses coupled to eight science-grade commercial CCD cameras. The lenses are mounted on a common framework and are coaligned to simultaneously image the same position on the sky. The system provides an imaging capability equivalent to a 0.4 m aperture f/1.0 refractor with a 2.6° × 1.9° field of view. The system is driven by custom software for instrument control and robotic operation. Data is collected with noncommon optical paths through each lens, and with careful tracking of sky variations in order to minimize systematic errors that limit the accuracy of background estimation and flat-fielding. The system has no obstructions in the light path, optimized baffling, and internal optical surfaces coated with a new generation of antireflection coatings based on subwavelength nanostructures. As a result, the array's point-spread function has a factor of ∼10 less scattered light at large radii than well-baffled reflecting telescopes. The Dragonfly Telephoto Array is capable of imaging extended structures to surface brightness levels below μB = 30 mag arcsec-2 in ∼10 h integrations (without binning or foreground star removal). This is considerably deeper than the surface brightness limit of any existing wide-field telescope. At present, no systematic errors limiting the usefulness of much longer integration times have been identified. With longer integrations (50-100 h), foreground star removal, and modest binning, the Dragonfly Telephoto Array is capable of probing structures with surface brightnesses below μB = 32 mag arcsec-2. The detection of structures at these surface brightness levels may hold the key to solving the \"missing substructure\" and \"missing satellite\" problems of conventional hierarchical galaxy formation models. The Dragonfly Telephoto Array is therefore executing a fully automated multiyear imaging survey of a complete sample of nearby galaxies in order to undertake the first census of ultrafaint substructures in the nearby universe.
Journal Article
Descemet membrane endothelial keratoplasty combined with presbyopia‐correcting and toric intraocular lenses – a narrative review
Fuchs endothelial corneal dystrophy (FECD) is the leading indication for EK and may coexist with cataract and presbyopia. Notably, the outcomes of phacoemulsification in FECD patients are not as favorable as those in eyes without this condition. Historically, only monofocal intraocular lenses (IOLs) were recommended for these patients. However, recent reports have described the implantation of Premium-IOLs (such as Multifocal IOLs, Enhanced Depth of Focus IOLs, and Toric IOLs) in FECD eyes undergoing cataract surgery and Descemet membrane endothelial keratoplasty (DMEK). While the results are encouraging, they are not as optimal as those from unoperated eyes, especially when comparing simultaneous procedures to sequential ones. It’s advised to perform the DMEK first to improve the accuracy of IOL calculations. Still, even successfully operated eyes may experience secondary graft failure or graft rejection after DMEK. The success rate of a secondary DMEK is typically lower than that of the initial procedure. Furthermore, if the postoperative thickness after DMEK is less than anticipated, laser enhancements might not be an option. There’s a pressing need for more controlled and randomized clinical trials to ascertain the safety and effectiveness of Premium-IOLs for FECD eyes. This narrative review aims to collate evidence on the use of Premium IOL technologies in eyes receiving EK and to underscore key points for surgeons performing EK combined with cataract surgery.
Journal Article
Quantitative assessment of photic phenomena in the presbyopia-correcting intraocular lens
This was a prospective study to evaluate the feasibility of the photic phenomena test (PPT) for quantifying glare, halo, and starburst. We compared two presbyopia-correcting intraocular lenses (IOLs), the Symfony IOL and the PanOptix IOL, as well as the monofocal Clareon IOL in 111 IOL-implanted eyes of 111 patients who underwent the PPT 1 month postoperatively. The reproducibility of photic phenomena with the PPT was assessed in 39 multifocal IOL-implanted eyes of 20 patients and among the examiners. Patients with ocular diseases, except for refractive errors, were excluded. The mean values of the groups were evaluated. Bland–Altman plots were used to analyze statistical data (Easy R version 1.37; R Foundation for Statistical Computing, Vienna, Austria). The PPT reproducibility assessment revealed no fixed bias or regressive significance. Reproducibility was confirmed. The glare size did not differ significantly between the Symfony, PanOptix, and Clareon groups. The halo size was significantly larger in the Symfony group (p < 0.01) than in the PanOptix group. The halo intensity was significantly brighter in the PanOptix group (p < 0.01) than in the Symfony group. In contrast, no halos were perceived in the Clareon group. The starburst size or intensity did not differ significantly between the Symfony, PanOptix, and Clareon groups. We identified the photic phenomenon related to various IOLs.
Journal Article
Update on Contact Lens Treatment of Keratoconus
Keratoconus (KC) is a progressive disease that leads to a decrease in visual acuity and quality and impairs vision-related quality of life. Contact lens (CL) application has a primary place and importance in the correction of the optic problems due to the disease. The corneal changes and increased irregular astigmatism that occur with KC progression necessitate special CL designs and fitting methods. In addition to disease stage, the patient's lens tolerance also plays a role in the application of CLs in KC patients. With recent advances in materials and design technology, the CLs used in the treatment of KC have developed considerably and there are various types available. In this review, we discuss the wide range of CLs, including rigid and soft lenses, hybrid and scleral lenses, and even custom lens designs, in light of recent scientific advances. Keywords: Keratoconus, contact lenses, rigid gas-permeable lenses, soft lenses, piggyback lenses, hybrid lenses, scleral lenses
Journal Article