SciCombinator

Discover the most talked about and latest scientific content & concepts.

Concept: Dioptre

27

To establish a corneal correction equation for the Shammas post-hyperopic laser in situ keratomileusis (LASIK) (Shammas-PHL) formula and to evaluate its accuracy in cases with and without available pre-LASIK data.

Concepts: Laser, Eye, Cornea, Refractive surgery, Lens, LASIK, Intraocular lens, Dioptre

22

This study aims to develop a new optical design method of soft multifocal contact lens (CLs) to obtain uniform optical power in large center-distance zone with optimized Non-Uniform Rational B-spline (NURBS). For the anterior surface profiles of CLs, the NURBS design curves are optimized to match given optical power distributions. Then, the NURBS in the center-distance zones are fitted in the corresponding spherical/aspheric curves for both data points and their centers of curvature to achieve the uniform power. Four cases of soft CLs have been manufactured by casting in shell molds by injection molding and then measured to verify the design specifications. Results of power profiles of these CLs are concord with the given clinical requirements of uniform powers in larger center-distance zone. The developed optical design method has been verified for multifocal CLs design and can be further applied for production of soft multifocal CLs.

Concepts: Optics, Lens, Contact lens, Corrective lens, Focal length, Dioptre, Interpolation, Splines

7

Among 4- and 5-year-old children, deficits in measures of attention, visual-motor integration (VMI) and visual perception (VP) are associated with moderate, uncorrected hyperopia (3 to 6 diopters [D]) accompanied by reduced near visual function (near visual acuity worse than 20/40 or stereoacuity worse than 240 seconds of arc).

Concepts: Eye, Vision, Visual perception, Visual system, Visual acuity, Eyeglass prescription, Book of Optics, Dioptre

1

Varifocal lenses, conventionally implemented by changing the axial distance between multiple optical elements, have a wide range of applications in imaging and optical beam scanning. The use of conventional bulky refractive elements makes these varifocal lenses large, slow, and limits their tunability. Metasurfaces, a new category of lithographically defined diffractive devices, enable thin and lightweight optical elements with precisely engineered phase profiles. Here we demonstrate tunable metasurface doublets, based on microelectromechanical systems (MEMS), with more than 60 diopters (about 4%) change in the optical power upon a 1-μm movement of one metasurface, and a scanning frequency that can potentially reach a few kHz. They can also be integrated with a third metasurface to make compact microscopes (~1 mm thick) with a large corrected field of view (~500 μm or 40 degrees) and fast axial scanning for 3D imaging. This paves the way towards MEMS-integrated metasurfaces as a platform for tunable and reconfigurable optics.

Concepts: Optics, Refractive index, Microscope, Frequency, Lens, Microelectromechanical systems, Focal length, Dioptre

0

For in vivo mouse retinal imaging, especially with Adaptive Optics instruments, application of a contact lens is desirable, as it allows maintenance of cornea hydration and helps to prevent cataract formation during lengthy imaging sessions. However, since the refractive elements of the eye (cornea and lens) serve as the objective for most in vivo retinal imaging systems, the use of a contact lens, even with 0 Dpt. refractive power, can alter the system’s optical properties. In this investigation we examined the effective focal length change and the aberrations that arise from use of a contact lens. First, focal length changes were simulated with a Zemax mouse eye model. Then ocular aberrations with and without a 0 Dpt. contact lens were measured with the Shack-Hartmann wavefront sensor (SHWS) in a customized AO-SLO system. Total RMS wavefront errors were measured for two groups of mice (14-month, and 2.5-month-old), decomposed into 66 Zernike aberration terms, and compared. These data revealed that vertical coma and spherical aberrations were increased with use of a contact lens in our system. Based on the ocular wavefront data we evaluated the effect of the contact lens on the imaging system performance as a function of the pupil size. Both RMS error and Strehl ratios were quantified for the two groups of mice, with and without contact lenses, and for different input beam sizes. These results provide information for determining optimum pupil size for retinal imaging without adaptive optics, and raise critical issues for design of mouse optical imaging systems that incorporate contact lenses.

Concepts: Optics, Eye, Cornea, Lens, Adaptive optics, Focal length, Dioptre, F-number

0

To evaluate changes in regional corneal epithelial thickness after corneal crosslinking (CXL) using higher fluence (7.2 J/cm2) and accelerated treatment time (4 minutes) in eyes with progressive keratoconus using spectral-domain optical coherence tomography (SD-OCT) and to correlate focal epithelial and focal anterior curvature changes.

Concepts: Optics, General relativity, Cornea, Dioptre

0

To evaluate changes in corneal tomography after stromal lenticule implantation ex vivo, with respect to the dependency of the lenticule thickness and implantation depth on the corneal curvature and the postoperative biomechanical strength at increased chamber pressure.

Concepts: In vivo, Eye, Cornea, Dioptre

0

Current corneal assessment technologies make the process of corneal evaluation extremely fast and simple. Several devices and technologies allow to explore and manage patients better. Optical coherence tomography (OCT) technology has evolved over the years, and hence a detailed evaluation of anterior segment (AS) structures such as cornea, conjunctiva, tear meniscus, anterior chamber, iris, and crystalline lens has been possible in a noncontact and safe procedure. The purpose of this special issue is to present and update in the evaluation of cornea and ocular surface, and this paper reviews a description of the AS-OCT, presenting the technology and common clinical uses of OCT in the management of diseases involving cornea and ocular surface to provide an updated information of the clinical recommendations of this technique in eye care practice.

Concepts: Optics, Eye, Visual perception, Cornea, Sclera, Lens, Iris, Dioptre

0

Corneal inlays are a relatively new treatment option for presbyopia. Using biological inlays, derived from lenticules extracted from small incision lenticule extraction, may offer advantages over commercialized synthetic inlays in the aspect of biocompatibility. We conducted a non-human primate study to evaluate the safety, predictability, efficacy and tissue response after autogeneic, decellularized xenogeneic and xenogeneic lenticule implantation. The lenticule implantation effectively resulted in central corneal steepening (simulated keratometric values increased by 1.8-2.3 diopters), central hyper-prolate changes (asphericity Q values changed by -0.26 to -0.36), corneal anterior surface elevation (7.7-9.3 μm) and reasonable effective zone (1.5-1.8 times of the lenticule physical diameter), with no differences among the three groups. Slit lamp microscopy, transmission electron microscopy, confocal microscopy, histology and immunohistochemistry analyses confirmed the biocompatibility of the autogeneic and decellularized lenticules, whereas one eye in the xenogeneic group developed corneal stromal rejection during the study period. Our results showed that lenticule implantation has the potential for the management of presbyopia, and provide the basis for future clinical studies. The decellularization process may increase the potential utilization of lenticules without changing the efficacy.

Concepts: Electron, Effectiveness, Histology, Eye, Primate, Change, Microscopy, Dioptre

0

Despite the global pandemic of myopia, the precise molecular mechanism of the onset of myopia remains largely unknown. This is partially because of the lack of efficient murine myopic models that allow genetic manipulation at low cost. Here we report a highly practical and reproducible lens-induced myopia model by specially designed frames and lenses for mice. A lens power dependent myopic induction in mice was shown until minus 30 diopter lenses. The phenotype was significantly stronger than form-deprivation myopia. We presented the protocol for precise evaluations of the state of myopia, including refraction, corneal curvature and axial length using up-to-date devices. We also found that myopic mouse eyes showed decreased visual acuity on optokinetic response examination. Finally, we confirmed the anti-myopic effect of 1% atropine using this model, which showed its potential in drug screening. The strong phenotype, stable evaluation and the potential for gene manipulation utilizing the presented method in mice will accelerate the translational research of myopia.

Concepts: DNA, Gene, Cornea, Lens, Eyeglass prescription, Contact lens, Refractive error, Dioptre