Lens Technology (China)

We discuss the requirements, concepts, simulations, implementation, and calibration of two dual Fabry-Perot (FPI)-based imaging spectropolarimeters, CRISP and CHROMIS, at the Swedish 1-m Solar Telescope, and CRISP2, which is under construction. These instruments are optimised for a large field of view and high cadence at the expense of a moderate spectral resolution, and use a combination of a high-resolution and a low-resolution etalon together with an order-sorting prefilter to define the bandpass. The overall design is made robust and stable by tailoring the low-resolution etalon reflectivity to accommodate expected cavity errors from both etalons, by using a compact optical design that eliminates the need for folding mirrors, and enclosing the entire system within a single container sealed by lenses. By using a telecentric design based on lenses rather than mirrors, image degradation by the FPI system is negligible, as shown in a previous publication, and the throughput of the system is maximised. The initial alignment, and maintaining that alignment over time, is greatly simplified. Moreover, the telecentric design allows the full calibration and/or modelling of essential system parameters to be carried out without interfering with the optical set-up or the cameras. We also discuss briefly the polarimeters developed for CRISP and CHROMIS. The high performance of CRISP and CHROMIS has been demonstrated in an earlier publication through measurements of the granulation contrast and comparisons with similar measurements simultaneously made through broadband continuum filters. Here, we focus on the aspects of the design that are central to enabling high performance and robustness, but also discuss the calibration and processing of the data, and use a few examples of processed data to demonstrate the achievable image and data quality. We put forward a proposal for a similar conceptual design for the European Solar Telescope and conclude by discussing potential problems of the proposed approach to designs of this type. Some aspects of these FPI systems may also be of interest outside the solar community.

Claire McDonnell discusses the less frequently encountered cases of syndromic myopia

To adapt the Quality of Vision Questionnaire (QoV) for measuring negative dysphotopsia and to validate the original and modified versions in the Dutch population. The QoV was translated into Dutch according to standardized methodology. Negative dysphotopsia items were constructed based on focus group interviews, literature review and clinical data. The questionnaire was completed by 404 subjects, including contact lens wearers, patients with cataract and after cataract surgery (95.5% with a monofocal, 4.5% with a multifocal intraocular lens). Rasch analysis was applied for evaluation of reliability and validity of the original QoV and modified version, Negative Dysphotopsia QoV (ND-QoV). The frequency, severity and bothersome scales of the QoV and ND-QoV demonstrated good measurement precision, good fit statistics for all but one item, but significant mistargeting of more than one logit. Item estimations were stable across the study groups and scales were unidimensional with more than 50% of variance explained by the measurements. There was a positive correlation between questionnaire scores and best corrected visual acuity (r = 0.3, p < 0.01). The quality of vision measured by all three scales was significantly poorer (p < 0.01) in patients with negative dysphotopsia compared to asymptomatic pseudophakic patients. The Dutch version of the QoV questionnaire has shown good psychometric properties comparable to the native version as well as good reliability and validity. The addition of negative dysphotopsia items is a valuable modification for the reliable assessment of quality of vision in pseudophakic patients.

Sophie Taylor-West describes a case of rigid corneal lens intolerance solved by refitting with a scleral contact lens

Purpose: To compare the effect of blue block lenses and anti-reflection coated (ARC) on reading speed in visual display unit (VDU) and printed chart and on visual fatigue questionnaire.

In order to improve the wettability and antiprotein adsorption property of PDMS, heptamethyltrisiloxane (a well-known superspreader) was coated onto the PDMS substrates by a swelling–deswelling process. PDMS films were first immersed in heptamethyltrisiloxane solution mixtures to coat heptamethyltrisiloxane onto PDMS. During the deswelling process, the hydrophobic siloxane group of the superspreader heptamethyltrisiloxane was trapped in the PDMS matrix, while the hydrophilic group EO was exposed to the surface. In this manner, heptamethyltrisiloxane was finally coated on the PDMS surface via swelling–deswelling process. Contact angle measurements, optical property analyses, X-ray photoelectron spectroscopy, and atomic force microscopy were used to confirm that durable hydrophilic and transparent PDMS surfaces were successfully obtained. The PDMS surface wettability could be adjusted by tuning the solubility parameters of the solution mixture. Additionally, antiprotein adsorption property was investigated and the result indicated the heptamethyltrisiloxane was tethered onto the PDMS surface. The swelling–deswelling method can be applied for the modification of other crosslinked polymers to obtain antifouling surfaces and functional materials for biomedical applications. A superspreading surfactant (Silwet-L77) was coated onto the PDMS surface by the swelling–deswelling process, to improve its hydrophilicity and antiprotein adsorption properties.

The relationship between water (W) content and silicon (Si) content of silicone-hydrogel (SiHy) contact lens materials was inspected using identical methodologies, equipment, and operators for materials composing 16 types of commercially available SiHy contact lenses. Fluorine (F) content was included in the analysis for the three materials also containing a fluoropolymer. One type of lens consisted of a bulk SiHy material coated with thin layers of conventional hydrogel. SiHy materials were obtained in the form of 16 contact lens brands purchased on the open market in a common range of refractive powers from -3 to +6 D in single lots. All test lenses were equilibrated at room temperature in a standard saline recommended in the American National Standards Institute Z80.20-2016 and International Organization for Standardization (ISO) 18369-4:2017 standards. W content was obtained gravimetrically, in %, according to those standards for 16 lenses of each SiHy material. Si content was determined in % using inductively coupled plasma optical emission spectroscopy for four digested lenses of each material. F content was determined in % using an ion-selective electrode for four combusted lenses of each of the three fluorinated SiHy materials. W and Si contents of the bulk SiHy material of the coated lens were estimated by computational exclusion of the hydrogel layers. The linear coefficients of determination (R, n=16) were -0.7576 (relating mean dry Si content [n=4] to mean W content [n=16]) and -0.8819 (relating mean hydrated Si content [n=4] to mean W content [n=16]). When the 4 SiHy materials that were fluorinated or coated were excluded from the analysis, the R values (n=12) were -0.8869 and -0.9263, respectively. When F contents and the coating were added to the assessments, the linear coefficients of determination (R, n=16) became -0.8948 (relating mean dry [Si+F] content to mean W content) and -0.9397 (relating mean hydrated [Si+F] content to mean W content). There is a fundamental negative linear relationship between Si and W contents for SiHy contact lens materials above 35% W content that is followed when F content and hydrogel coatings are empirically added to the analysis below 35% W content. The relationship was tightest for hydrated (Si+F) content and W content, for which the regression equation had an R of -0.9397: (Si+F)=-0.3073 (W)+22.148. The relationship between (Si+F) and W therefore seems to be based on composition rather than structure of available SiHy contact lens materials.

Alkylating DNA Lesions Associated with Replication are Repaired by Homologous Recombination in Mammalian Cells

To monitor changes in corneal structure and level of inflammatory mediators in tears of myopic patients following orthokeratology (OK) and laser in situ keratomileusis (LASIK). Sixty-two myopic subjects were analyzed in this prospective study. Thirty-two had worn Paragon CRT contact lenses and 30 underwent standard LASIK. Thirty-two control subjects were also recruited. Pachometry and corneal topography were performed 12 months after both interventions. Tears were collected and assayed using ELISA for IL-6, IL-8, matrix metalloproteinase-9 (MMP-9), and epidermal growth factor (EGF). Corneal power decreased in the central area and increased in the paracentral area. Simultaneously, there was a central corneal thinning with mid-peripheral thickening for OK. No changes were observed for LASIK. In comparison with controls, IL-6, IL-8, MMP-9, and EGF levels were increased significantly for OK (P < 0.01). Only MMP-9 (P < 0.01) and EGF (P < 0.01) were increased for LASIK. Pro-inflammatory response was found to be associated with the degree of myopia in the OK group. The MMP-9 and EGF upregulation was linked to the presence of iron deposition in both groups, whereas increased levels of EGF were connected with the presence of myopic regression after LASIK. Both interventions involved important tissue reshaping. The physical presence of a reverse geometry contact lens caused certain markers to change significantly in comparison with no lens wear or LASIK in the long-term response. MMP-9 was significantly higher in tears of subjects presenting iron deposition after OK or LASIK, and EGF levels seemed to play an important role in postoperative refractive outcomes after LASIK.